UAV Quantitative Remote Sensing of Riparian Zone Vegetation for River and Lake Health Assessment: A Review

Abstract

River and lake health assessment (RLHA) is an important approach to alleviating the conflict between protecting river and lake ecosystems and fostering socioeconomic development, aiming for comprehensive protection, governance, and management. Vegetation, a key component of the riparian zone, supports and maintains river and lake health (RLH) by providing a range of ecological functions. While research on riparian zone vegetation is ongoing, these studies have not yet been synthesized from the perspective of integrating RLHA with the ecological functions of riparian zone vegetation. In this paper, based on the bibliometric method, the relevant literature studies on the topics of RLHA and unmanned aerial vehicle (UAV) remote sensing of vegetation were screened and counted, and the keywords were highlighted, respectively. Based on the connotation of RLH, this paper categorizes the indicators of RLHA into five aspects: water space: the critical area from the river and lake water body to the land in the riparian zone; water resources: the amount of water in the river and lake; water environment: the quality of water in the river and lake; water ecology:aquatic organisms in the river and lake; and water services:the function of ecosystem services in the river and lake. Based on these five aspects, this paper analyzes the key role of riparian zone vegetation in RLHA. In this paper, the key roles of riparian zone vegetation in RLHA are summarized as follows: stabilizing riverbanks, purifying water quality, regulating water temperature, providing food, replenishing groundwater, providing biological habitats, and beautifying human habitats. This paper analyzes the application of riparian zone vegetation ecological functions in RLH, summarizing the correlation between RLHA indicators and these ecological functions. Moreover, this paper analyzes the advantages of UAV remote sensing technology in the quantitative monitoring of riparian zone vegetation. This analysis is based on the high spatial and temporal resolution characteristics of UAV remote sensing technology and focuses on monitoring the ecological functions of riparian zone vegetation. On this basis, this paper summarizes the content and indicators of UAV quantitative remote sensing monitoring of riparian zone vegetation for RLHA. It covers several aspects: delineation of riparian zone extent, identification of vegetation types and distribution, the influence of vegetation on changes in the river floodplain, vegetation cover, plant diversity, and the impact of vegetation distribution on biological habitat. This paper summarizes the monitoring objects involved in monitoring riparian zones, riparian zone vegetation, river floodplains, and biological habitats, and summarizes the monitoring indicators for each category. Finally, this paper analyzes the challenges of UAV quantitative remote sensing for riparian zone vegetation at the current stage, including the limitations of UAV platforms and sensors, and the complexity of UAV remote sensing data information. This paper envisages the future application prospects of UAV quantitative remote sensing for riparian zone vegetation, including the development of hardware and software such as UAV platforms, sensors, and data technologies, as well as the development of integrated air-to-ground monitoring systems and the construction of UAV quantitative remote sensing platforms tailored to actual management applications.

1. Introduction

From ensuring environmental sustainability in the Millennium Development Goals (MDGs) to focusing on health and well-being, clean water, marine environments, and terrestrial ecology in the Sustainable Development Goals (SDGs), the global emphasis on the sustainable development of rivers and lakes has been highlighted in research. Since the 1980s, many countries have implemented ecological protection policies and enhanced water ecological monitoring, exemplified by management plans in the United States and Europe [1]. In the 21st century, more countries have established water ecological monitoring networks [2,3,4]. China also places great importance on this issue, maintains water health, and promotes ecological civilization through the nationwide implementation of the river and lake chief system [5].

Countries all over the world place great importance on the use and protection of water resources. On the one hand, they set up national Sustainable Development Goals for the use and protection of water resources [6,7,8]; on the other hand, they adopt a variety of scientific methods for the management, use, and protection of water resources [9,10,11]. This paper conceptualizes RLH from a scientific and systematic perspective, which is crucial for strengthening the management and protection of rivers and lakes, maintaining their health, and realizing the sustainable use of their functions.

As an important component of river and lake ecosystems, riparian zone vegetation is essential in RLHA systems. Since the 1970s, there has been a large number of reviews on riparian zone vegetation based on RLHA, covering a wide range of aspects such as ecological functions, environmental interactions, pollution control, and ecosystem services. On the one hand, scholars have focused on the interaction between vegetation and rivers, climate change, and greenhouse gas emissions [12,13,14,15,16]. Moreover, several scholars have studied ecological bank protection, riparian zone vegetation, and their role in water pollution control from different perspectives. Wang et al. focused on the development of ecological berms for non-point source pollution control, emphasizing the key role of vegetation in this with optimization methods [17]. Zhao et al. explored the removal mechanism of nitrogen pollution and its heterogeneity between submerged and riparian zones [18]. Wu et al. analyzed the role of riparian zone vegetation structures and mechanisms in the control of agricultural surface pollution [19]. Cai et al. summarized the research progress on the distribution of nitrogen and phosphorus in the riparian zones of inland water bodies in China, revealing the influence of water body interactions on nitrogen and phosphorus distribution [20]. Chen et al. studied the physiological and ecological responses of desert riparian zone vegetation under drought stress [21]. In addition, some other scholars focused on the ecological functions of riparian zone vegetation. Hoppenreijs et al. explored the potential impacts of anthropogenic activities on riparian zones in the Northern Hemisphere and the main processes affecting their vegetation composition [22]. Prado et al. researched the ecosystem services in riparian zones from 2000 to 2020, analyzed the countries and journals with the highest number of publications, and summarized the ecological functions of riparian zone vegetation primarily studied in the literature [23]. By summarizing the ecosystem functions provided by riparian zone vegetation, Singh et al. suggested integrated management of riparian zone to maintain RLH in the context of current environmental changes [24]. Scheuerell and LeRoy studied the effect of plant gender on riparian zone plant communities and ecosystems [25]. There are also several overview discussions on riparian zone vegetation from the perspective of remote sensing technology [26].

In general, scholars have failed to summarize the ecological function of riparian zone vegetation from the perspective of RLH, whether regarding the extent of the riparian zone, the interaction between riparian zone vegetation and the environment, or the ecological functions of the vegetation itself. In addition, advancements in information technology have promoted the development of RLH information technology, but due to the technical capabilities of the time, research on the process mechanism related to RLH is very limited. Currently, in the context of the intelligent era, the remote sensing technology of unmanned aerial vehicles is flourishing, significantly influencing the evolution of RLHA concepts, the innovation of technology, and the robustness of the assessment system.

Based on the bibliometric method, this paper screens, counts, and analyzes keywords, highlighting related literature on the two topics of RLHA and UAV remote sensing of vegetation. On the one hand, based on the connotation of RLH, this paper summarizes the indicators of RLHA and analyzes the key role of riparian zone vegetation in RLHA. By analyzing the application of riparian zone vegetation’s ecological function in RLH, this paper summarizes the correlation between RLHA indicators and the riparian zone vegetation’s ecological function. Moreover, based on the characteristics of UAV remote sensing technology, this paper analyzes the advantages of UAV remote sensing technology in quantitative remote sensing monitoring of riparian zone vegetation from the perspective of monitoring the ecological function of riparian zone vegetation. On this basis, this paper summarizes the content and monitoring indicators of UAV quantitative remote sensing monitoring of riparian zone vegetation for RLHA and summarizes the monitoring indicators covered by the monitoring objects in the monitoring content. Finally, this paper analyzes the challenges of UAV quantitative remote sensing for riparian zone vegetation at the present stage and looks forward to the future application prospects of RLHA in the era of ecological civilization, thereby contributing to the development of the RLHA system.

2. Materials and Methods

2.1. Documentation

In this paper, based on bibliometrics, the Web of Science Core Collection was used as the data source to collect the literature related to RLHA from 2004 to 2023. In analyzing the literature, the above analysis was achieved through software called CiteSpace, which mainly includes the aggregation of keywords in the literature, the timeframe of their occurrence, the conceptual progression, and transformation of keywords. In addition, it provides other information such as the year of publication, the country of the first author, and other features included within the software [27]. In addition, to ensure the completeness of the retrieved literature, two subject terms—water ecosystem health assessment and aquatic ecosystem health assessment—were added to this paper. In this paper, a total of 5109 literature studies were retrieved by using TS = (river and lake health assessment) OR TS = (water ecosystem health assessment) OR TS = (aquatic ecosystem health assessment) as the search formula. On this basis, this paper classifies the retrieved literature from five aspects: water space, water resources, water environment, water ecology, and water services, and analyzes the research hotspots related to RLHA in each aspect through five keywords: water space, water resources, water environment, water ecology, and water services. The research hotspots related to the RLHA in each area are analyzed.

2.2. Characteristics of the Issuance

2.2.1. Annual Number of Publications

Here, by analyzing the research intensities of different areas such as water space, water resources, water environment, water ecology, and water services under the framework of river and lake health, and identifying the respective research hotspots within each area, we can discern the overall trends and focal points in river and lake health research as a whole. In terms of the number of annual publications (Figure 1), the number of publications around the topic of RLHA shows a growing trend, with the number of publications increasing from 31 in 2004 to 788 in 2023, with an average annual growth rate of 18.56%. Among them, the five areas—water space, water resources, water environment, water ecology, and water services—all have different degrees of growth in the number of published articles. Moreover, the literature on water resources, water environment, and water services has seen a significant increase since 2017, accounting for 57% of the total number of publications by 2023.

2.2.2. Nation

This article analyzes relevant literature studies published in each country to gauge the level of importance attached to river and lake health and the development stage of river and lake health within those countries, setting the stage for focused case studies on river and lake health in the subsequent sections. The ten countries with the highest number of publications, in order, are China, the United States, India, Australia, Canada, the United Kingdom, Italy, Germany, Spain, and France. Among them (Figure 2), the total number of publications from China and the United States equals that of the other eight countries. Starting in 2018, China’s share of annual publications began to exceed that of the United States, and on average, for each year from 2018 to 2023, China’s annual publications accounted for more than 35% of the total annual publications of the ten countries.

2.2.3. Keyword Analysis

This paper analyzes the keywords in the search results (Figure 3), and the results show that RLHA has always been a research area of concern for scholars. The research on RLHA has changed from focusing on water quality to focusing on solving the problems of environmental management. At this stage, scholars are more concerned with the topics related to solid-phase extraction, wastewater treatment, and emerging contaminants, including the use of new technologies for the treatment of water pollutants and the study of new types of pollutants.

Scholars have paid more attention to the impact of human activities on RLH. On the one hand, human activities have damaged the river and lake ecosystems and resulted in pollutants [28]; on the other hand, human beings have caused damage to RLH while managing the river and lake ecosystems [29]. However, research on the process mechanisms of river and lake ecosystems in RLH assessments is incomplete. It is primarily analyzed from the perspective of the response of aquatic organisms to ecosystem health (Figure 3) and does not pay attention to the riparian zone, which is the important area where pollutants pass through before entering the ecosystems of rivers and lakes. Of these, studies on water space appeared less frequently before 2011, and research at this stage focuses on aspects such as the management of riparian zones [30] (Figure 3b); studies on water resources now mainly focus on the conversion of surface water to groundwater [31] and the use of water resources in urban riparian zones [32] (Figure 3c); studies on the water environment have focused on the management of novel pollutants such as organics [33] and antibiotics [34] (Figure 3d); studies on water ecology have focused on ecosystem health [35], risk assessment [36], etc. (Figure 3e); studies on water services have focused on land use change [37], soil [38], and microbial degradation [39] that can positively contribute to the ecosystem service functions of rivers and lakes (Figure 3f). In general, riparian zone vegetation is located in the transition zone between river and lake ecosystems and terrestrial ecosystems, which can intercept surface source pollutants from entering rivers and lakes and reduce the risk of river and lake pollution, so it is very important for the study of riparian zone vegetation [17].

3. RLHA

3.1. Progress in RLHA Research

Since the 1980s, water environment management policies in developed countries in Europe and America have begun to emphasize ecological protection and the quality of water ecology in river basins. They have conducted a series of RLH monitoring and evaluation research programs with aquatic organisms at the core. In 1984, the UK introduced a prediction and classification system for river and lake invertebrates, which predicted the distribution of macroinvertebrate communities in rivers and lakes under natural conditions using regional characteristics. The biological status was assessed by comparing the fauna observed in the field with the predicted fauna to evaluate the health status of rivers and lakes [40]. In 1992, Australia launched the National River and Lake Health Program and developed the Australian River and Lake Assessment Program based on the predictive model approach of the UK River and Lake Invertebrate Prediction and Classification System. This system uses aquatic macroinvertebrates to conduct RLH Assessments [41]. In 2000, the European Union issued the European Water Framework Directive, which elevated water ecological management to a legal standard. EU member states have conducted extensive research and practice in water ecological assessment and watershed management [42], shifting the development of management objectives from single pollution control to the protection of the integrity of the entire ecosystem.

3.2. Indicators for RLHA

This paper analyzes RLHA programs implemented by major countries and organizations through a review of the development of RLHA, from which indicators selected by countries for RLHA were filtered (

Table 1. Evaluation indicators in typical RLHA programs in selected countries and organizations.

Countries and Organizations	Implementation Program	Primary Indicators	Secondary Indicators
United States	National Rivers and Streams Assessment	Biological indicators	Benthic macroinvertebrate community
			Fish community
		Chemical indicators	Nutrients
			Acidification
			Salinity
		Physical indicators	In-stream fish habitat
			Riparian disturbance
			Riparian vegetation cover
			Streambed sediments
		Human health	Algal toxins
		indicators	Enterococci bacteria
			Mercury in fish tissue plugs
			Fish tissue contamination in rivers
European Union	Internationally Coordinated	Ecological Status
	Management plan 2022–2027 for the International River Basin District of the Rhine	Ecological potential
		Chemical status
		Quantitative status
China	Scoring rules for water ecology	Water ecosystem	Number of fish species
	Assessment indicators in the Yangtze River Basin. (River water ecology assessment indicators)	health	Number of aquatic organisms under priority protection
			Number of macrobenthic species
		Aquatic habitat	Natural shoreline ratio
		protection	Water column connectivity
			Aquatic Habitat Anthropogenic Impact Index
			Quality of ecosystems in water-holding areas
		Water environmental	Combined pollution status
		protection	Pollution intensity during flood season
		Water security	Ecological flow compliance rate
	Scoring Rules for water ecology	Water ecosystem	Number of fish species
	Assessment indicators in the Yangtze River Basin. (Lake water ecology assessment indicators)	health	Number of aquatic organisms under priority protection
			Number of macrobenthic species
			Proportion of area covered by water bloom
			Percentage of aquatic vegetation cover
			zooplankton community structure
		Aquatic habitat	Natural shoreline ratio
		protection	Aquatic Habitat Anthropogenic Impact Index
			Quality of ecosystems in water-holding areas
		Water environmental protection	Integrated Nutritional Status
		Water security	Ecological flow compliance rate

) [43,44,45]. Various countries and organizations have adopted different indicators for RLHA. The National Rivers and Streams Assessment in the United States believes that healthy rivers and lakes can enhance people’s quality of life by providing drinking water, irrigating crops, facilitating navigation, and offering recreational activities, while also serving as shelter, food, and habitat for birds and wildlife. The evaluation indicators are thus categorized into four types: biological, chemical, physical, and human health indicators. The EU’s Internationally Coordinated Management Plan 2022–2027 for the International River Basin District of the Rhine has implemented several measures to address the pollution of the Rhine, significantly reducing point source pollution compared to the past. Point-source pollution is now significantly lower than in the past. Today, the main sources of pollutant and nutrient pollution are surface runoff and mining activities in the Rhine catchment area, as well as the climate change that Europe is experiencing. Therefore, the health of the Rhine was evaluated in terms of four aspects: ecological status, ecological potential, chemical status, and quantitative status. In China, a pilot river and lake health assessment was conducted in the Yangtze River, and scoring rules for water ecology assessment indicators were released for the Yangtze River Basin. These indicators are established in four categories: water ecosystem health, aquatic habitat protection, water environment protection, and water resources security.

The United States, as a country that paid attention to RLHA at an early stage, plays a role in RLHA in subsequent countries, whether in the pertinence of the RLHA program or the comprehensiveness of the RLHA index system. Based on the RLHA of each member state, the European Union introduced the landmark European Water Framework Directive in 2000, which elevates water ecological management to a legal standard. The management objective is to protect the integrity of the entire ecosystem. Following the introduction of the RLHA concept, China is also actively exploring the establishment of an RLHA system that aligns with its national conditions.

In general, each country faces different practical problems at different stages of development, and the RLHA system needs to progress and develop accordingly. Starting from the basic connotation of RLH and combined with the current research status and hotspots of RLHA, this paper summarizes the indicators of RLHA into five aspects: water space (which focuses on the process of river and lake water to the riparian zone land process), water resources (which measure the amount of water in the river and lake), water environment (which evaluates the quality of water in the river and lake), water ecology (which protects aquatic organisms in the river and lake), and water services (which maintain the functions of river and lake ecosystem services). This paper analyzes the key components of riparian zone vegetation in RLHA from these five aspects.

4. Riparian Zone Vegetation

4.1. Riparian Zone and Riparian Zone Vegetation

A riparian zone is one of the 15 terrestrial biomes in the world, which serves as a transition zone for the exchange of matter, energy, and information, and can intercept surface source pollutants from entering rivers and lakes, thereby reducing the risk of pollution. Additionally, riparian zones provide essential resources and habitats for survival, regulate the climate, offer opportunities for sightseeing and tourism, etc. [46]. With the in-depth study of riparian zones, the construction, protection, and management of riparian zones have received more attention. In the 1960s, the United States began to study riparian zones by formulating guidelines and regulations for the protection and construction of riparian zones, putting forward a variety of quantitative methods for calculating the widths of riparian zones, including the ecosystem management model of riparian zones, and clarifying the range of the width of riparian zones [47]. The widths and functional attributes of riparian zones are influenced by river size, river location, hydrology, and geomorphology. Hydrology is a powerful factor in regulating the structural and functional aspects of riparian zones [48]. It also controls the path of the water flow in the riparian zone. Five main characteristics of water flow—season, time, frequency, rate of change, and magnitude—are considered important factors in shaping plant communities in riparian zones. Riparian zone vegetation differs from other terrestrial vegetation in terms of structure due to the influences of river moisture, flooding, and soil properties [49,50,51]. River morphology, groundwater, and hydrological processes have significant impacts on the life cycle of riparian zone vegetation [52].

4.2. Ecological Functions of Riparian Zone Vegetation

Riparian zone vegetation protects and maintains RLH by providing a range of ecological functions [53,54,55]. Riparian zone vegetation can stabilize riverbanks, buffer sediments, and pollutants, regulate river and lake temperatures, provide ecological corridors, food, and habitat for wildlife, enhance groundwater recharge, and beautify human habitats [26].

4.2.1. Stabilizing Riverbanks

Streambank instability and the resulting sediment load can have deleterious effects on the overall ecological health of river and lake ecosystems [56]. Riparian zone vegetation root networks enhance soil cohesion through a mixture of physical and hydrological effects, thereby increasing streambank stability and helping to reduce streambank erosion [57]. In terms of physical effects, riparian zone vegetation strengthens the soil through the root system [58]. Whereas, in terms of hydrological effects, riparian zone vegetation reduces soil moisture through canopy interception and evapotranspiration, and the growth of riparian zone vegetation hinders river flow and reduces the average flow velocity, thereby affecting sediment erosion [59].

4.2.2. Purifying Water Quality

Riparian zone vegetation purifies the water quality of rivers and lakes by filtering nutrients such as nitrogen and phosphorus from sediments [60,61]. Riparian zone vegetation improves water quality through physical, chemical, and biological processes [62,63]. In physical processes, vegetation enhances hydraulic roughness, which reduces surface flow, increases infiltration rates, and promotes sediment and nutrient deposition in the riparian zone. In chemical processes, riparian zone vegetation alters the redox potential and aids in nutrient transformation, which leads to nutrient loss and release. In biological processes, riparian zone vegetation reduces nutrient concentrations by assimilating nutrients into plant biomass or by microbial immobilization.

4.2.3. Regulating Water Temperature

Water temperature is critical to RLH [64,65,66,67]. Most aquatic organisms are thermostatic; therefore, water temperature affects their metabolic rate, growth, development, survival, and distribution [66]. For example, water temperature affects the growth, survival, and population characteristics of cold water-adapted fish [68]. Riparian zone vegetation regulates river and lake temperatures by shading the river and lake and reducing incident solar radiation [69]. Geographic location, groundwater inputs, and the composition, density, and width of riparian zone vegetation determine the extent to which riparian zone vegetation influences river and lake temperatures [70]. Riparian zone vegetation also controls the dense growth of aquatic macrophytes through canopy shading [71].

4.2.4. Providing Food

Riparian zone vegetation can also input a large amount of dead leaves, fruits, etc. into rivers and lakes, providing food for microorganisms in rivers and lakes [72], as well as food sources for fish [73] and other organisms [74] in rivers and lakes. Studies have shown that riparian zone vegetation contributes a large amount of organic matter to rivers and lakes annually, becoming the primary source of food and energy for river and lake organisms [75,76].

4.2.5. Replenishing Recharge

Riparian zone vegetation facilitates the exchange between surface water and groundwater [63]. Riparian zone vegetation has direct access not only to water from rivers and lakes but also to groundwater flowing into or out of rivers and lakes. Water enters the soil through the root hairs of the vegetation and enriches the aquifer. Riparian zone vegetation enhances the infiltration capacity of the soil, thus allowing water to infiltrate into the aquifer [77]. Riparian zone enhances evapotranspiration and rainfall interception while reducing surface runoff [78]. These effects enhance the relationship between baseflow and runoff, suggesting that riparian zone vegetation plays a key role in groundwater recharge. Deadfall from this vegetation also significantly contributes to groundwater recharge, with surface aprons retaining more water and improving infiltration into the soil compared to bare soil [79].

4.2.6. Providing Biological Habitats

Riparian zones are one of the terrestrial biophysical habitats on Earth [80]. Landscape attributes of riparian zone vegetation, such as proximity to water sources, nutrient availability, diverse vegetation structures, and conditions of low light and cold temperatures, are important factors that support biodiversity [80,81,82]. Riparian zone vegetation provides habitat for a wide range of organisms, from plants, algae, and insects to fish, migratory and resident birds. Among them, riparian zone vegetation is considered an important habitat for migratory and resident birds [82]. For migration, water, food, safety, rest, shelter, breeding, nesting and roosting, dispersal, or movement between habitat patches, birds choose riparian zone vegetation [83,84,85,86]. Riparian zone vegetation is a habitat for various invertebrates, including dung beetles, ground-scavenging ants, and butterflies [80,87]. Riparian zone vegetation also serves as a crucial shelter for conservation efforts [80].

4.2.7. Beautifying Human Habitats

The rich vegetation resources of wetland, grassland, and forest ecosystems in the riparian zone enhance the landscape effect of the watershed. The transition zone between land and water, in particular, possesses high ornamental value, providing people with experiences of beauty and sensory enjoyment [88].

4.3. Correlation between the Ecological Function of Riparian Zone Vegetation and Indicators for RLHA

Riparian zone vegetation can provide a wealth of ecological functions that are closely related to RLH (

Table 2. Correlation between the ecological function of riparian zone vegetation and indicators for RLHA.

Ecosystem Services of Riparian Zone Vegetation	RLHA
Stabilizing riverbanks	Water space
Purifying water quality	Water environment
Regulating water temperature
Providing food	Water ecology
Providing biological habitats
Replenishing groundwater	Water resources
Beautifying human habitats	Water services

). It is important to analyze the role that ecological functions play in RLH and to analyze the changes that occur in RLH by monitoring the changes in ecological functions, for better RLHA. In this paper, the relevance of each ecological function of riparian zone vegetation to the connotation of RLHA is analyzed.

Stabilizing riverbanks mainly affect the water space in RLHA. In the riparian zone, plant morphological properties, biomechanical properties, and spatial distribution significantly influence water flow characteristics, sediment transport and trapping, soil development and fertility, and geomorphic stability. These factors collectively contribute to riparian stability [89,90,91,92]. In addition, river and lake water levels change with seasonal and weather changes, and changes in water levels can contribute to riparian instability, which is mitigated by the presence of vegetation [93].

Purifying water quality primarily impacts the water environment in RLHA. Riparian zone vegetation directly absorbs and stores nutrients from the water. As dead plants decompose, nutrients are released, helping to improve soil quality.

Regulating water temperature primarily affects the aquatic ecology in RLHA. Water temperature limits the growth and survival of aquatic organisms; therefore, the shading provided by riparian zone vegetation plays a crucial role in inhibiting the warming of water flows. Riparian zone vegetation mitigates the adverse effects on ecosystems by providing shade to prevent excessive heating [94,95].

Providing food mainly affects the water ecology in RLHA. Aquatic organisms depend on organic matter provided by riparian zone vegetation. This organic matter is mainly in the form of apoplastic leaves, which, once in the water, are subject to decomposition by microbial decomposers, increasing the source of nutrients for macroinvertebrates, and contributing to increased macroinvertebrate diversity [72].

Replenishing groundwater primarily affects the water resources in RLHA. Water is transferred from deep soils to overlying dry soils through plant root systems. In addition to being influenced by gravity, soil moisture can be actively transported downward from the surface to deeper soil layers through the plant root system, which maintains root vigor, promotes root growth in dry soils, and alters water allocation.

Providing biological habitats primarily influences the water ecology in RLHA. The physical structures of most terrestrial habitats are controlled by plant communities, and riparian zones are transitional areas between terrestrial and aquatic ecosystems that support high levels of biodiversity by providing unique microclimate and habitat conditions. Riparian zone vegetation can change the habitat structures for reptiles and amphibians, as well as geomorphological types of habitats [96], and influence microclimatic conditions such as temperature and humidity, which are important for insect abundance.

Beautifying human habitats mainly affects the water services in RLHA. On the one hand, the riparian zone, as a transitional area between terrestrial and aquatic ecosystems, serves as a crucial link for the exchange of energy, materials, and information. This is essential for maintaining ecosystem stability and providing living space for organisms. Moreover, recreational activities in riparian zones bring people closer to nature, offering a space for stress relief and relaxation [88,97].

5. UAV Quantitative Remote Sensing of Vegetation in Riparian Zone

Since the 1980s, with the development of satellite remote sensing technology, large-scale spatial and temporal monitoring of riparian zone vegetation has become possible. However, due to the high cost of launching satellites, most satellite data have long been available at a high cost [98], except for a few datasets like the Landsat series, which are partially free. During this period, many remote sensing index methods based on the spectral features of ground targets have primarily used free Landsat satellite data, with other satellite data being used to a lesser extent.

In addition to high costs and limited availability, remote sensing satellite data are constrained by several other factors. The observation capability of remote sensing satellites is determined by their sensors; once a satellite is launched, its sensors cannot be replaced, meaning the satellite’s observation performance cannot be improved during its life cycle. Moreover, remote sensing satellites can only observe targets directly beneath them and while traveling along their orbital paths, limiting the ability to capture targets from specific angles. Optical remote sensing satellites, which rely on visible and infrared light reflected from the observation target, are also affected by lighting conditions. For panchromatic, multispectral, and hyperspectral satellites, poor lighting can severely degrade observation quality, and effective remote sensing images can only be obtained when the satellite is over the target and lighting conditions are good [99]; for optical remote sensing satellites, meteorological conditions, such as cloud cover, will also affect the observation results [100]. As remote sensing satellites are far away from ground targets, the spatial resolution values of their images are usually low, and even if there are image data with resolution values better than 1 meter, their coverage is limited and the acquisition cost is high [101]. These constraints not only limit the scope of remote sensing research but also affect the direction of research. In recent years, the emergence of UAVs has gradually improved the above limitations of remote sensing research.

5.1. UAV Remote Sensing

Since the 20th century, UAV technology has seen significant development, with Chinese UAVs at the forefront globally. UAV manufacturers, such as DJI Innovation, Zongheng Automation, and Pegasus Robotics, have led the application of UAV remote sensing technology across various fields, such as land surveying, environmental monitoring, geological surveys, and emergency disaster relief [102]. Nowadays, UAVs have become mainstream aerial remote sensing platforms due to their low cost, high intelligence, mobility, and flexibility [103]. After development in recent decades, UAVs, along with small remote sensing sensors and data processing software, have made great progress and now play a key role in remote sensing technology [104]. This paper analyzes the main research content and current status of UAV remote sensing technology at this stage, focusing on RLHA indicators and the ecological functions of riparian zone vegetation.

5.2. Riparian Zone Vegetation and UAV Quantitative Remote Sensing Monitoring Content

Riparian zone vegetation affects changes in river and lake morphology [49]. At the same time, riparian zone vegetation can increase biodiversity [105], provide protection for endangered species, serve as a breeding ground for species, and limit pollution [17]. The management of riparian zone vegetation has been increasing, and scientific research in this area has followed suit. As a result, managers and scientists require tools that can effectively sense, characterize, and monitor vegetation quality while operating efficiently in riparian zones. The spatial and temporal complexity of vegetation cover makes it challenging to develop generalized tools for this purpose. Currently, there are two main approaches to vegetation monitoring: image analysis [106] and field surveys [107]. Over the past few decades, improvements in resource availability and image diversity have led to significant advances in image analysis techniques. Moreover, enhanced computer processing power, geographic information system technology, and the availability of advanced image analysis software have contributed to these advancements. As a result, image analysis and remote sensing techniques are now widely used in resource management and vegetation research [26].

In this paper, based on bibliometrics, literature related to UAVs and vegetation was screened, and 3889 documents were screened by constructing the search formula TS = (UAV) AND TS = (vegetation), and the screened documents were analyzed. In terms of the number of annual publications, studies on UAVs and vegetation show a growing trend (Figure 4), with an annual growth rate of 41.23% from 2004 to 2023. Among them, from 41 articles in 2014 to 706 articles in 2023, there was a 16-fold increase. In terms of the countries to which the authors of the literature belong, China, the United States, Spain, Italy, Germany, Australia, Brazil, the United Kingdom, Canada, and Japan are the ten countries with the highest number of publications, in that order. The U.S. was an early leader in researching related content and has consistently been at the forefront in terms of the number of articles published. However, since 2010, China has steadily increased its number of publications. In 2018, China surpassed the United States in annual publications, and by 2023, China accounted for 40% of the total annual publications of all countries in the world.

By analyzing the keywords, it can be seen that current research on UAVs and vegetation primarily focuses on the application of UAV remote sensing data for vegetation information extraction (Figure 5a). As shown in Figure 5b, on the one hand, scholars have approached this in two ways: first, by analyzing and mining UAV remote sensing data to study the type and distribution of vegetation, and second, by focusing on the inversion of vegetation parameters based on UAV remote sensing technology. These parameters include leaf area index, plant biomass, chlorophyll content, and so on.

Through the above analysis of the current state and research hotspots in UAV and vegetation studies, this paper summarizes the content of UAV quantitative remote sensing monitoring of riparian zone vegetation for RLHA, based on RLHA indicators and the ecological functions of riparian zone vegetation (Figure 6). The monitoring content mainly includes the delineation of riparian zone extent, vegetation type and distribution, the influence of vegetation on changes in the river floodplain, vegetation cover, plant diversity, and the impact of vegetation distribution on biological habitats.

5.2.1. Riparian Zone Extent Delineation

To understand the accuracy of riparian zone vegetation identification, it is necessary to consider the accuracy and extent of channel boundary locations. UAV remote sensing imagery with centimeter-level spatial resolution provides favorable conditions for accurate extraction of channel boundary information, but factors such as the direction of river flow [108] and image shading can affect the accuracy of channel boundary delineation. In fixed-width riparian zone reaches, the accuracy of the channel boundary is particularly important because it directly affects the accuracy of the riparian zone reach. In variable-width riparian zone reaches, the accuracy of the channel boundary does not directly affect the accuracy of the riparian zone extent because the extent of the riparian zone is derived directly from the digital elevation model rather than the channel boundary [109]. However, it is still important to accurately determine the channel location, as this can be used to validate the variable width riparian zone extent by confirming the channel’s location. The direction of river flow has little effect on the accuracy of channel boundary delineation. The higher the river terrace and the wider the channel, the greater the accuracy of boundary delineation. Riparian zone vegetation identification studies should prioritize improving the accuracy of narrower channel boundary delineation, which would significantly enhance the overall accuracy of channel boundary mapping. It has been noted that image shading affects the accuracy of mapping applications. A study by Ge Pu et al. found that image shading does impact the delineation of river boundaries, making it more challenging to accurately define river channels in shaded areas [110]. A combination of LiDAR and deep learning models can be used to effectively improve the accuracy of channel boundary delineation in narrower rivers [111]. Williams et al. recently combined terrestrial laser scanning with optical bathymetry to produce a continuous DTM of a braided river system [112]. UAVs can monitor changes in morphology throughout the river channel more accurately than traditional methods, having an accurate, high-resolution river DTM [113].

5.2.2. Vegetation Type and Distribution

Riparian zone vegetation is the most important factor interacting with the physical characteristics of the river channel, its morphological dynamics, and its flow regime. Remote sensing provides continuous datasets that help to determine the spatial coverage and functional structural complexity of vegetation [106]. Several scholars have interpreted RGB photographs of riparian zone vegetation [114,115] and classified surface features into basic textural categories such as bare ground, water, deciduous forest, coniferous forest, and herbaceous.

UAVs are suitable for riparian zone vegetation studies because they have a finer scale [116]. UAVs can now be equipped with a variety of sensors such as the visible band, multispectral and hyperspectral sensors, and LiDAR. Among them, RGB images are widely used due to their convenience, speed, and low price. Some studies have achieved mapping vegetation cover dynamics by UAVs equipped with RGB cameras [117]. Some studies have identified watersheds, vegetation, and gravel based on UAV RGB images and multispectral imagery using supervised classification methods such as maximum likelihood classification, random forests, or convolutional neural networks [118,119]. Therefore, vegetation distribution research using UAV images has become a very promising research direction.

5.2.3. Influence of Vegetation on Changes in River Floodplain

Riparian zone vegetation is closely related to changes in river floodplains. Riparian zone vegetation is studied to assess the interrelationships between vegetation and channel dynamics. Targeted monitoring related to channel morphology and vegetation can be used to understand changes in river floodplains, with studies focusing on comparing the effects of land cover class and channel parameters on changes in river floodplains [120,121,122,123]. In addition, several studies have explored the relationship between river morphology and vegetation type, as well as the effects of floods and high-intensity events [124,125,126] or post-dam hydrological alterations on riparian zone vegetation and rambling [127,128,129].

The development of UAVs has greatly improved the identification and monitoring of riparian zone vegetation [130,131]. UAVs help to monitor fluvial geomorphological evolution as well as changes in river morphology during flood events [113,132,133]. Among others, Rusnák et al. outlined an overview of fluvial geomorphological studies using UAV technology, fully demonstrating the potential of UAV application in studying riverine floodplain changes [126].

5.2.4. Vegetation Cover

The traditional vegetation cover survey method in the riparian zone is based on a manual field survey, and the survey process is limited by traffic conditions, geographic environments, weather, and other restrictions, which cannot cover the whole study area. The results of the survey deviate from the actual situation. With the development of satellite remote sensing technology, spatial–temporal large-scale remote sensing monitoring of vegetation cover has become the preferred choice, and is widely used because it can avoid the bias generated by manual field surveys [26].

UAVs have great potential for monitoring riparian zone vegetation as they can frequently produce detailed maps of greenness and vegetation height [134]. Over time, these height and greenness attributes can improve the classification accuracy of riparian zone vegetation, as these characteristics exhibit specific seasonal changes depending on the vegetation type [134]. A study on riparian zone vegetation classification based on UAV imagery demonstrated that spectral and vertical structural variables were the most discriminating factors [135]. Point cloud data and LiDAR data derived from UAV RGB imagery have been mainly used for elevation change mapping, showing vertical accuracy of 5–8 cm for bare surfaces [136,137]. Bendig et al. extracted barley height using a crop surface model from UAV RGB imagery, with a vertical error of 0.25 m [138]. For natural vegetation, UAV-derived DSM can be used to estimate vegetation height with an error range of 0.17–0.33 m.

5.2.5. Plant Diversity

Riparian zones are important areas for biodiversity. Riparian zone vegetation provides a range of ecosystem services such as soil and water conservation, nutrient retention, and transformation [139]. However, groundwater extraction and severe water scarcity are detrimental to the growth and development of riparian zone vegetation and have led to a reduction in riparian zone habitats [140]. Therefore, understanding the spatial structure of riparian zone vegetation is important for protecting and restoring riparian zone plant diversity [141].

Traditional field surveys of riparian zone vegetation can provide detailed information on site-specific biodiversity, but they usually require significant time and resources and can be very expensive when sampling large areas [142]. Limited by the spatial extent and temporal frequency, it is difficult for field surveys to obtain information on plant diversity on a large scale [143,144]. Remote sensing has the advantage of collecting information on a large scale [145,146]. However, herbaceous plants in riparian zone vegetation, which are small in satellite remote sensing images, are difficult to distinguish, so UAV remote sensing technology becomes useful. In particular, the rapid development of UAV remote sensing technology in recent years [147,148] has provided a new means for plant diversity monitoring [149]. In the past decades, many remote sensing methods for plant diversity monitoring have been proposed and developed [150,151]. In general, methods for estimating plant diversity using remotely sensed data are categorized into two approaches: direct identification of plant species and their distributions through visual interpretation or image classification algorithms, and the derivation of species distributions by establishing relationships between biodiversity and remotely sensed spectral data [152].

5.2.6. Influence of Vegetation Distribution on the Biological Habitat

The abundance and distribution of fauna depend on riparian zone vegetation and its structure [153]. Remote sensing data monitors land cover in riparian zones based on water level classes and vegetation distribution, establishing links between physical indicators and parameters derived from satellite data [154]. Some scholars have primarily focused on classifying potential habitats based on remotely sensed data [155], examining habitat changes due to vegetation shifts [156], or identifying parameters to be used in the calculation of habitat richness indices. Arantes et al. [157] and Mollot and Bilby [158] have combined habitat data, environmental data, and remotely sensed mapped landscape structures together to determine habitat preferences and assess habitat conditions. In addition, several studies have focused on determining habitat suitability indices [159], ground nesting probabilities, their reflection in environmental constraints [160], the use of vegetation indices in multispectral imagery as predictors of insect habitat [161,162], and bird abundance [163].

In recent years, the development of UAV remote sensing technology has provided new powerful tools for wildlife monitoring [164,165,166]. UAV remote sensing technology is capable of low-intensity interference, precise location, accurate counting, and close observation of wildlife, providing a data source for wildlife conservation [167,168]. In addition, UAVs are increasingly used for waterfowl surveys and monitoring, including evaluating the nesting status of canopy breeding birds [169], identifying bird species [170], locating ground nests of songbirds [171], and counting bird populations [172,173].

5.3. Indicators for Quantitative Remote Sensing Monitoring of Vegetation in Riparian Zone by UAV

This paper analyzes the correlation between RLHA indicators and the ecological function of riparian zone vegetation. It summarizes the monitoring content of UAV quantitative remote sensing for riparian zone vegetation and outlines the monitoring objects involved: riparian zone, riparian zone vegetation, floodplains, and bio-habitats. The paper also details the monitoring indicators for each category of monitoring objects (

Table 3. Objects and indicators of quantitative remote sensing monitoring of riparian zone vegetation by UAV.

Monitoring Content		Monitoring Indicators	Sensor Type
Riparian zone	Direct indicators	River Boundary	RGB
		Topography around the river	Lidar
		River landscape	RGB, Multispectral, Hyperspectral
	Indirect indicators	Riparian zone extent	——
Riparian zone vegetation	Direct indicators	Individual vegetation	RGB, Multispectral, Hyperspectral
		Vegetation type	RGB, Multispectral, Hyperspectral
	Indirect indicators	Vegetation cover	——
		Plant diversity	——
		Biomass	——
River floodplain	Direct indicators	Channel topography	Ground penetrating radar
		Water depth	Ground penetrating radar
		Turbidity and suspended sediment	RGB, Multispectral, Hyperspectral
	Indirect indicators	Channel change	——
		Land cover	——
Biological habitats	Direct indicators	Water velocity	RGB, Lidar
		Water temperature	Thermal infrared
	Indirect indicators	Biological Habitat	——

). These indicators are divided into two types: direct indicators, which can be monitored directly, and indirect indicators, which are calculated from the direct indicators.

Firstly, delineating the extent of the riparian zone is crucial because its accuracy impacts the identification of riparian zone vegetation. This extent is analyzed by monitoring the river boundary, surrounding topography, and the landscape of the river and lake. Secondly, monitoring of riparian zone vegetation involves four main aspects: individual vegetation, vegetation type, vegetation cover, and plant diversity. Through UAV remote sensing technology, it is possible to extract the vegetation individuals and types, as well as derive the vegetation coverage and plant diversity. Again, the study of the river floodplain focuses on comparing the influence of riparian zone vegetation and river channel parameters on the floodplain’s changes. On the one hand, the temporal change of the river floodplain should be analyzed, which involves the river channel, the topography of the river channel, and the hydrodynamics of the river; on the other hand, the response of the surrounding land cover should be analyzed during the change of the river floodplain. By monitoring the river channel’s topography, depth, turbidity, and suspended sediment content, the analysis will determine the relationship between river channel changes and the surrounding land cover. Moreover, the response of the surrounding land cover should be analyzed by observing these same factors. Finally, biological habitat is an important aspect of RLHA. At this stage, more analysis is conducted in areas where the river flows more slowly and where there are significant differences in water temperatures, to indirectly assess whether the environment is suitable and biologically viable.

6. Challenges and Prospects

6.1. Existing Challenges

This article summarizes the existing challenges of UAV remote sensing technology in the context of the above practical application of quantitative UAV remote sensing of vegetation in riparian zones.

6.1.1. Insufficient Research on RLH

This study shows that UAV-based RLH research is more concerned with the application of UAV remote sensing data in the extraction of information on river and lake water quality [174], vegetation monitoring in riparian zones [175], plant diversity [176], aquatic habitats [177], etc., but not the process mechanisms by which UAVs play a role in RLHA from the perspective of RLHA, based on the integrity of river and lake ecosystems.

6.1.2. Limitations of UAV Platforms and Sensors

• Insufficient stability.
  When UAVs fly in complex environments, they are susceptible to interference from external factors such as airflow and precipitation, which leads to unstable flight attitudes and affects the quality of remote sensing data collection [178]. The riparian zone vegetation, located near rivers and lakes, often lies in complex terrains like mountains and hills. In such areas, UAV flights demand that pilots maintain clear visibility of the UAV or equip the UAV with obstacle avoidance sensors. Pilots must navigate carefully, striving to maintain a safe distance from the ground to ensure the safety of the flight.
• Shorter range.
  The limited battery capacity of a UAV results in a short single flight time, making it difficult to meet the demand for long-duration, wide-area remote sensing monitoring [179]. The riparian zone generally stretches from the upstream to the downstream of a river, spanning from a few to thousands of kilometers. For effective monitoring of riparian zone vegetation, UAVs must have long endurance. Additionally, in areas of the riparian zone that are inaccessible to personnel, UAVs are also required to have a prolonged flight time to facilitate long-distance monitoring.
• Insufficient load.
  The limited payloads of UAVs restrict their ability to carry multiple high-precision and high-performance sensors at the same time, which restricts the efficiency of riparian zone vegetation monitoring [180]. Vegetation monitoring in the riparian zone requires visual assessments of the vegetation using RGB cameras as well as analyses of vegetation growth conditions through multiple sensors, including multispectral, hyperspectral, radar, thermal infrared technologies, and so on.

6.1.3. Complexity of Information in UAV Remote Sensing Data

• Complexity of data processing.
  Data obtained from UAV remote sensing monitoring need to be processed and analyzed, and for the identification of riparian zone vegetation, it is necessary to accurately identify individual vegetation and distinguish vegetation types. There are high requirements for algorithms and software.
• Data real-time.
  For the riparian zone, which is an area with more drastic changes and not obvious change characteristics, the lagging interpretation of remote sensing monitoring data will not be able to guide the riparian zone management and other applications in a timely manner, and it is necessary to solve the challenges associated with data transmission and the timely processing of data to realize real-time monitoring of the riparian zone vegetation. The application of real-time data for UAVs is still in its infancy [181,182,183] and will be a hotspot for UAV application research.
• Universality of algorithms and models.
  The spatial resolution of image data acquired by UAV remote sensing is better than 1 centimeter. Compared with satellite-based remote sensing, it can reflect more detailed and complex subsurface types and features. This poses a challenge to the universality of algorithms and models used for extracting vegetation parameter information. Most current algorithms or models are only applicable to specific research and lack stability, universality, and generality, which restricts their application and promotion across a wide range of fields. For riparian zones under different climatic conditions, the vegetation types and parameters vary. It is necessary to select and adjust the model parameters according to local conditions to achieve regional adaptability. Algorithms and models based on UAV data are now hotspots of research [101,184,185,186,187], and future research should continue in this direction.

6.2. Application Prospects

6.2.1. Improvements in UAV Flight Platforms

In response to the challenge of vegetation in the more complex riparian zone environment, the UAV flight platform could be further enhanced in the future. This includes improving the stability of the UAV to adapt to rainfall, high winds, and other complex weather conditions. In addition, further improvements can be made to adapt to the characteristics of the natural environment by, on the one hand, improving the stability of the signal so that it will not be lost due to the terrain and vegetation, causing mission failure, and on the other hand, improving the flexibility of the UAV, which can only fly horizontally, and should be given a more flexible flight mode to avoid obstacles.

6.2.2. Improvements in UAV Sensors

UAVs are generally only capable of acquiring data from one sensor at a time, which greatly limits the efficiency of the UAV. Future research can start with the development of integrated sensors so that UAVs can realize multiple sensor data acquisition in one flight.

6.2.3. Advances in UAV Information Processing Technology

The information contained in UAV remote sensing data is informative and complex. Currently, the analysis of UAV remote sensing data has improved based on methods used in satellite remote sensing. With the advancement of new technologies such as machine learning and artificial intelligence, scholars should, in the future, propose information processing techniques specific to UAV remote sensing data. For example, scene modeling and other methods could be developed that are well-suited to the characteristics of UAV remote sensing technology. In addition, the detailed nature of UAV remote sensing data should be fully utilized to accurately depict the refined structure of research subjects, such as vegetation in riparian zones, including the transfer and flow of matter, energy, and information at the microscopic scale.

6.2.4. Integrated Air-to-Ground Monitoring

The most widely used areas of integrated space-heaven monitoring technology are water quality monitoring and water resource surveys. Traditional water quality monitoring is conducted through water quality monitoring stations or field deployment points. However, the distribution of these points is limited and not suitable for large-scale development, making it challenging to capture the characteristics of the spatial distribution of pollutants. Remote sensing monitoring, through UAVs and satellite images, allows for the assessment of river water quality across entire river basins, facilitating dynamic monitoring and distribution of information on water quality. Water resource surveys primarily rely on data from hydrological stations, employing mathematical statistics principles and methods. Water quantity is calculated through hydrological analysis, but the limited and uneven distribution of hydrological stations somewhat restricts the accurate calculation of water quantities. The total amount of surface water resources in a region can be obtained based on remote sensing surveys and unmanned boat underwater topographic measurements.

6.2.5. Construction of a Platform for the Quantitative Remote Sensing of Vegetation in Riparian Zones by UAVs

With the continuous maturation and popularization of UAV technology, the operation and maintenance of UAVs will gradually become autonomous in the future. Through the establishment of remote monitoring centers and intelligent airport maintenance platforms for UAVs, remote monitoring, fault diagnosis and automatic maintenance of UAVs can be achieved, reducing operation and maintenance costs and improving operation and maintenance efficiency. UAVs will have stronger autonomous navigation and intelligent identification capabilities and will be able to autonomously plan routes, adjust flight attitudes, and collect data according to preset tasks. At the same time, through the integration of intelligent algorithm models, UAVs can achieve real-time analysis and early warning of monitoring data, thereby improving emergency response speed. Building on this technology, a real-time monitoring platform for riparian zone vegetation can be established, combining meteorological data and hydrological data of rivers and lakes to predict changes in riparian zone vegetation and effectively manage and protect riparian zone vegetation.

7. Conclusions

7.1. RLHA System

Based on bibliometrics, this paper comprehends the development history of RLHA, analyzes RLHA programs implemented by major countries and organizations, summarizes and analyzes a series of indicators selected for RLHA, and clarifies the five aspects of the RLHA system, namely, water space, water resources, water environment, water ecology, and water services.

7.2. Ecological Functions of Riparian Zone Vegetation

This paper analyzes riparian zone vegetation to clarify the importance of riparian zone vegetation in river and lake ecosystems from the perspective of RLHA. The ecological functions of riparian zone vegetation are summarized in this paper as stabilizing riverbanks, purifying water quality, regulating water temperature, providing food, replenishing groundwater, providing biological habitats, and beautifying human habitats.

7.3. Indicators for Quantitative Remote Sensing Monitoring of Vegetation in Riparian Zones by UAVs

This paper summarizes the content of UAV quantitative remote sensing monitoring of riparian zone vegetation for RLHA, based on RLHA indicators and the ecological function of riparian zone vegetation while incorporating the research hotspots of UAV remote sensing of vegetation. The monitoring content primarily includes the delineation of riparian zone extent, vegetation type and distribution, the influence of vegetation on river floodplain changes, vegetation cover, plant diversity, and the impact of vegetation distribution on biological habitats. The paper outlines the monitoring contents, the monitoring objects involved—such as the riparian zone, riparian zone vegetation, river floodplain, and biological habitats—and the monitoring indicators associated with each category of monitoring objects.

7.4. Challenges and Perspectives of Quantitative Remote Sensing of Vegetation in Riparian Zones by UAVs

In this paper, we address some existing challenges of UAV quantitative remote sensing for riparian zone vegetation monitoring, primarily focusing on the difficulties encountered by UAV remote sensing technology. In addition, this paper anticipates and envisions future applications of UAV remote sensing for riparian zone vegetation, including developments in the hardware and software of UAV platforms, sensors, information, and data technology. We also address the application of air–heaven integration monitoring, and the construction of a UAV remote sensing platform for quantitative monitoring of riparian zone vegetation in practical management.