Rooting for effective reforestation: landscape context and woodland cover

By Dr Matthew Dennis

Native broadleaf woodland in the UK stands at 14.5% land-cover compared to 40% for Europe as a whole. Government targets aim to reach 17% by 2030 – a huge increase on the ground in a short space of time. In this article, Dr Matthew Dennis demonstrates how the question of where to create new woodland is key to ensuring new woodlands provide an antidote to ongoing biodiversity loss in the UK.?

• Planners and policymakers tasked with woodland restoration face challenges in where to locate new woodlands.
• University of Manchester research analysed two conflicting approaches – larger, more connected patches of woodland, or more numerous smaller, fragmented patches.
• The opportunistic acquisition of land for reforestation needs to be balanced – reforestation strategy should be led by the landscape context.

Branching out – where to locate new woodlands

Current debates in landscape ecology centre on whether large areas of intact habitat are needed for effective nature conservation or whether smaller more numerous patches can achieve the same levels of protection. The answer to this question is relevant at all scales of landscape management and could help land managers, conservation trusts and local authorities make more informed and cost-effective decisions around nature protection.

This is of particular importance given the recent requirement for local authorities in the UK to develop Local Nature Recovery Strategies to address wide-spread biodiversity loss. A key component in the challenging task of reversing biodiversity loss is the restoration of native broadleaf woodland, one of our most threatened habitats. However, land-use pressures including the need for timber (through the plantation of non-native woodland), agriculture and increasing area required for human settlements make the problem of planning new woodland ever more complex. At the heart of this complexity is the question of where? If space is limited, how should we attempt to fit new woodland into already complex landscape mosaics?

Can’t see the wood for the trees? Conflicting approaches

Historically, protected habitat design has called for a bigger, better, more joined-up approach, underpinned by ideas from island biogeography, landscape ecology and, government white papers . However, recent evidence within conservation biology research has split scientists between those calling for the prioritisation of fewer larger patches and those who argue that fragmentation (smaller more numerous patches) promotes greater species richness .

The adoption of either of these perspectives could limit the options available to planners and landscape managers seeking to restore nature through woodland creation. Therefore, ?knowledge of whether large, connected patches of woodland or a more fragmented pattern delivers greater chances of nature recovery is key to the effective assigning of resources. A prime example of a large woodland restoration project that would benefit from such knowledge is the recently proposed Northern Forest . The Northern Forest is an ambitious reforestation project pledging to plant at least fifty million trees across the North of England covering just over ten thousand square miles. The area covers multiple gradients of urbanisation, agricultural intensity and tree cover.

University of Manchester research – getting to the root of the problem

Research carried out through the University of Manchester CASTOR project shows that the ability of woodland to support biodiversity is shaped by the intensity of the surrounding land-use.

The question we explored in our research was how gradients of different non-habitat land-use (often referred to as the “matrix” in landscape ecology studies) might determine whether large, connected patches or more numerous small woodland patches are better for wildlife.

Specifically, we looked at woodland mammals as this group is particularly sensitive to habitat loss and fragmentation. When we looked at these species, we found that in areas of the Northern Forest landscape that are dominated by grassland, or whenever cover by urban or arable land-use was low, the bigger, better, more-joined up approach did not perform as well as expected. In such contexts, any pattern of increasing woodland cover will do, with a greater number of patches usually leading to greater species richness. However, in areas subject to high urbanisation, larger, better-connected patches were optimal (because large patches and ease of movement between them is required to buffer against negative edge-effects).

Another key finding of our study was the strongly homogenising effect of arable land-use. We found that, as cover by arable land-use increased, overall land-cover diversity reduced, along with mammalian species richness. This means, in landscapes dominated by crops, the pattern of woodland in the landscape is relatively unimportant from a nature recovery perspective and efforts should be made instead to diversify the surrounding land-cover as much as possible (for example, by incorporating hedgerows, wood pasture, scrublands and patches of native woodland).

In a nutshell – policy recommendations

These findings can be directly integrated into planning policy, with particular relevance for large-scale landscape restoration. Within such contexts a range of woodland creation options should be employed and opportunistic acquisition of land for reforestation should not be the only consideration in restoration schemes. Instead, restoration should be led by the landscape context.

For example, in grassland landscapes, opportunistic planting of new woodland may be appropriate and woodland increase of any size and shape ought to be encouraged. In more hostile contexts such as where urbanisation is high, resources should be directed at large and well-connected woodland patches, otherwise nature recovery efforts may be wasted. Similarly, in areas undergoing restoration that are dominated by crop production, aiming at pre-determined patterns of woodland cover is less important than ensuring the sufficient provision of a diversity of resources in the wider landscape.

DEFRA and landscape planners should therefore work to increase land-cover diversity in addition to woodland creation, and they should consider adopting the following:

• Large connected patches when urbanisation is high (“negative edge-effects”)
• Increasing the amount and number of woodland patches when the surrounding matrix is more benign (e.g. in grassland landscapes).
• Increasing land-cover diversity when crop production dominates.

Our team’s research strongly indicates that these policymakers should prioritise woodland creation protocols aimed at nature recovery and tailored to the context of restoration rather than simply based on opportunistic land acquisition.