Upscaling biodiversity - ecosystem functioning research using intertidal forests as a model system (BEF-SCALE)

Human activities have already raised global species extinction rates a thousand-fold and have pushed an additional million species towards extinction. Biodiversity is also rapidly changing on more local scales as climate change drives the redistribution of species, and pressures such as overharvesting and habitat fragmentation intensify in many areas. Understanding how biodiversity influences ecosystem functions, such as carbon capture and fisheries productivity, is a crucial challenge directly relevant to meeting the UN sustainable development goals, and UK policy imperatives of harnessing biodiversity to achieve sustainable economic growth and using nature-based solutions to help meet 'net-zero' emissions by 2050.

Since the mid- 1990s, several hundred experiments have tested how changes in biodiversity influence ecosystem functions and services, with many studies indicating that biodiversity loss does not reduce functioning as long as the single best-performing species is retained. However, these studies have focused on local-scale interactions between species in small habitat units such as grassland plots, field enclosures, or aquarium tanks; we therefore lack studies that consider BEF relationships on the larger landscape-, regional- or even national- scales most relevant to the public, ecosystem managers, and policy makers. Ecological theory suggests that biodiversity is more important for ecosystem services as scale increases due to greater environmental variation, but it cannot currently be evaluated in real ecosystems because we lack BEF studies across scales and environmental gradients.

In this project we aim to bridge the gap between experiments and relevant larger scales by using Great Britain's intertidal forests as a model system. These highly productive and valuable ecosystems occur extensively around the GB's varied and complex coastlines and are formed by a manageable suite of seaweed species which can be easily manipulated across multiple distinct environmental gradients.

To meet our overall aim, we will incorporate multiple environmental factors into experiments, observations and models delivered across three inter-linked work packages which together provide a generalised approach and scaling relationships for BEF.

Our first work package uses a 100km stretch of the south Wales coastline - which incorporates gradients in wave exposure and turbidity - as an accessible template to experimentally test the causal effect of intertidal forest biodiversity on ecosystem functioning from small patches to the whole coastline. Our second package combines a network of standardised observations in intertidal forests around GB, with satellite remote sensing and statistical modelling, to test how BEF relationships scale-up -- from 1 m to 1000km scales -- in naturally assembled communities. The third and final work package uses the new experimental and observational data to inform dynamic models, allowing us to test how species traits such as dispersal and environmental tolerances interacts with environmental variability to determine BEF relationships across scales. A key innovation here is the explicit - and empirically informed - integration of spatial environmental variability in multiple environmental factors. These will be generalised to represent how the environment varies in a range of different ecosystems from forests, to agricultural landscapes, and to coral reefs.

The advancement of our project aim will deliver a revised appreciation of the role of diversity in ecosystems and demonstrate a generalizable approach for upscaling biodiversity - ecosystem functioning relationships. We anticipate that this will feed into predictions for how biodiversity changes will influence ecosystem functioning and services on large, relevant- scales, in intertidal forests and beyond, with a range of applications from natural capital models, to the design of large-scale ecosystem restoration projects.