Fast-tracking nature recovery by restoring forest habitat complexity

There is growing awareness that restoring natural ecosystems is essential if we are to mitigate climate change, curb rapid biodiversity declines and transition to a more sustainable future. In countries like the UK – where tree cover is lower than almost all other developed nations – nature restoration has largely become synonymous with forest creation and expansion. Trees form structurally complex canopies that not only store substantial amount of carbon in their stems and branches, but also provide irreplaceable habitat for countless species. Moreover, the physical scaffolding created by tree crowns also profoundly alters microclimatic conditions within and beneath the canopy – decreasing temperature fluctuations and extremes by several degrees, increasing moisture availability and modifying light environments. In turn, these shifts in microclimate shape local biodiversity and the biological processes it underpins by directly constraining the physiology, behaviour and demography of organisms. However, we currently have a very limited understanding of how these key axes of habitat complexity – canopy 3D structure and microclimate – recover over time following forest restoration. Nor do we know how different approaches to forest creation – such as active tree planting and natural colonisation – differ in their structural, microclimatic and biodiversity recovery trajectories. This knowledge gap fundamentally limits our ability to guide large-scale restoration interventions and maximise their outcomes for both nature and people. The overarching goal of this project is to generate the first comprehensive picture of how tree planting and natural colonisation drive the recovery of canopy 3D structure, microclimate, biodiversity and associated ecosystem processes during the critical first few decades of restoration in temperate forests. To achieve this goal, we will use a powerful combination of two complementary approaches: a fully replicated 60-year chronosequence of planted and naturally colonised forest landscapes in southern England, and whole-forest manipulative experiments where we will alter canopy 3D structure in a targeted way to determine the cascading impacts on microclimate, biodiversity and soil nutrient cycling. To fully characterise habitat complexity, we will use cutting-edge terrestrial laser scanning technologies to generate detailed 3D models of forest canopies and a network of over 1000 microclimate sensors providing continuous measurements of temperature and humidity throughout the full vertical profile of the canopy and soil. We will then combine this unprecedented picture of habitat complexity with comprehensive biodiversity data generated using field surveys, ecoacoustic and eDNA, as well as detailed measurements of key processes related soil carbon and nutrient cycling. In doing so we aim to mechanistically link temporal shifts in biodiversity and ecosystem functioning that occur during woodland creation to changes in habitat complexity – addressing a fundamental ecological question that has its origins in the 1950s and that today has direct applications to forest restoration, conservation and management. Our work will inform the UK’s ambitious national forest expansion strategy, which aims to add 30,000 ha of new forests each year as part of efforts to meet national net zero and biodiversity net gain targets. By working in partnership across academia and government, our project will deliver a series of practical recommendations and tools that enhance the ecological and social value of newly created forests in the UK and beyond – benefitting researchers, policy makers, the forestry sector, NGOs and other land managers.