Two major global initiatives have set ambitious goals for ecological restoration over the next decade. The Convention on Biological Diversity (CBD) has the objectives of restoring ecosystems critical for vital ecosystem services, enhancing carbon storage through forest restoration and restoring 15% of the world’s degraded ecosystems all by 2020. Similarly Reducing Emissions from Deforestation and Degradation (REDD+) aims to enahance carbon forest storage and reduce biodiversity loss, partly through forest restoration.
These are worthy goals, but they will only be achievable if there is social and political will to achieve them. However, quite apart from this problem these goals also raise vital questions for applied ecologists. One of these is, how good are we at actually restoring ecosystem services?
The honest answer is that it’s difficult to tell. Apart from carbon storage and pollination most services are extremely difficult to measure. However, by considering some ecosystem functions, such as nutrient cycling, to be intermediate ecosystem services (those that support the final benefits to human well-being) we can estimate some of the potential impacts of restoration.
A meta-analysis of restoration projects carried out by Jose Rey Benayas and colleagues did just that 1. They compared measures of biodiversity and intermediate ecosystem services in degraded, restored and relatively undisturbed reference sites. Restored sites showed a 25% increase in intermediate ecosystem service provision compared to degraded sites . However, restoration sites showed approximately 20% lower provision of services when compared to reference sites .
We appear to be relatively good at restoring biodiversity when compared to function – measures of biodiversity were 43% higher in restored than degraded sites, while they were 15% lower in restored compared to reference sites. A recent meta-analysis looking at restoration in wetlands produced remarkably similar results with functions being restored to 75% of reference levels 2.
Given this evidence, restoration appears to be relatively good at restoring ecosystem function. However, different ecosystems vary in how they respond to restoration with forests generally considered to be the amongst slowest to recover. Given that both the CBD and REDD+ initiatives target forest restoration to improve ecosystem service provision, this may be a slow process.
On the whole I would guess that we are probably better at restoring biodiversity than ecosystem services. Or at least we are better at restoring the biodiversity that people value and that is easily measurable. The are various reasons for this. Firstly, the primary goal of many restoration projects is to restore populations of particular species. Secondly, metrics of biodiversity are often easier to quantify than functions and particularly ecosystem services. Thirdly, we know more about limiting factors of species population size than how complex functions work and how these link to services.
Done well restoration can provide benefits to both nature and humans. Given that ecosystems survival ultimately depends on their relationship to the people that inhabit them, it is vital more work investigates how restoration alters the provision of ecosystem services.
1. Rey Benayas, J. M., Newton, A. C., Diaz, A., Bullock, J. M., & Benayas, J. M. R. (2009). Enhancement of biodiversity and ecosystem services by ecological restoration: a meta-analysis. Science, 325(5944), 1121-4.
2. Moreno-Mateos, D., Power, M. E., Comín, F. A., & Yockteng, R. (2012). Structural and functional loss in restored wetland ecosystems. PLoS biology, 10(1), e1001247. Public Library of Science. doi:10.1371/journal.pbio.1001247