Tree Hollows

Reforestation is an important tool for reducing or reversing biodiversity loss and mitigating climate change. However, there are many potential compromises between the structural (biodiversity) and functional (carbon sequestration and water yield) effects of reforestation, which can be affected by decisions on spatial design and establishment of plantings. We systematically review the environmental responses to reforestation and show that manipulating the configuration of plantings (location, size, species mix and tree density) increases a range of environmental benefits. More extensive tree plantings (> 10 ha) provide more habitat, and larger improvements to carbon and water cycling. Planting a mixture of native trees and shrubs is best for biodiversity while traditional plantation species, generally non-native species, sequester C faster. Tree density can be manipulated at planting or during early development to accelerate structural maturity and to manage water yields. A diversity of habitats will be created by planting in a variety of landscape positions and imitating the patchy distribution of forest types, which historically has characterized many regions. Areas with shallow aquifers can be planted to reduce water pollution or avoided to maintain water yields. Reforestation should be used to build forest networks that are surrounded by low-intensity land use and that provide links within regions and between biomes. While there are adequate models for C sequestration and changes in water yields after reforestation, the quantitative understanding of changes in habitat resources and species composition is more limited. Development of spatial and temporal modelling platforms based on empirical models of structural and functional outcomes of reforestation is essential for deciding on how to reconfigure agricultural regions. To build such platforms, we must quantify: (a) the influence of previous land uses, establishment methods, species mixes and interactions with adjacent land uses on environmental (particularly biodiversity) outcomes of reforestation; and (b) the ways in which responses measured at the level of individual plantings scale up to watersheds and regions. Models based on this information will help widespread reforestation for carbon sequestration improve native biodiversity, nutrient cycling and water balance at regional scales.

Hollow-bearing trees in native forests and woodlands are significant habitat resources for many Australian fauna but habitat removal, commercial timber harvesting and urban development continue to threaten these ecosystems. Protection for these habitats and their species is purportedly provided for in legislation, policy, and strategic management plans. However, public debate and disagreement surrounding forest management has resulted in the disintegration of national plans as interpreted by states and territories as well as individual stakeholders, resulting in gaps in policy implementation. This paper presents a hierarchical review of the current legislation and policy mechanisms underpinning forest conservation in Australia, with specific attention paid to important habitat features such as hollow-bearing trees. Apart from federal and state legislation acknowledging the importance of hollow bearing trees to biodiversity, sufficient mechanisms to halt the ongoing loss of this resource from Australian landscapes at the local level appear to be lacking. Hollow-bearing tree conservation strategies from 46 local councils in Victoria, New South Wales, Tasmania, and Queensland were reviewed. Very few (<5%) respondents  from local councils across all states indicated that they have specific plans for the conservation and management of hollow bearing trees, highlighting policy implementation gaps at the local level. Furthermore, apparent environmental management strategies and actions rank relatively low on local council priorities. Therefore, a stronger focus on conservation actions towards management of critical habitat features across the landscape supported by robust local, national, and international policy is needed.