This blog post discusses a recent paper by Mia Derhé, ‘Measuring the success of reforestation for restoring biodiversity and ecosystem functioning‘.

Restoring rainforests: Recovering both biodiversity and ecosystem functioning

Rapid anthropogenic forest change means that many countries are now running out of large areas of primary forest and so the future of tropical forest biodiversity depends more than ever on the effective management and restoration of human modified landscapes. Ecological restoration is therefore becoming increasingly applied in tropical forests to mitigate biodiversity losses and recover ecosystem functions.

What are we trying to recover and how do we measure it?

Ecological restoration can have a variety of intended outcomes, from increasing the abundance of certain threatened species, to improving soil stability or protecting watersheds. In order to determine the success of such projects, clear goals need to be set, and progress towards these pre-determined goals needs to be effectively assessed.

Two of the main goals of ecological restoration are the recovery of biodiversity and the recovery of ecosystem functioning, yet most researchers assume that increasing species diversity equates with an intrinsic recovery of ecosystem function, but this is very rarely tested and is not always the case. We need to understand the mechanistic link between biodiversity and ecosystem functioning in order to focus on restoring this relationship so that we can create healthy, stable ecosystems.

In a new paper published yesterday in the Journal of Applied Ecology, researchers from Lancaster University, CSIRO and the Queensland Museum show how diversity and ecosystem processes simultaneously respond to tropical forest restoration, and examine the mechanistic link between faunal diversity and ecological functions.

Simultaneous assessment of diversity and functioning

The researchers used pitfall traps to sample 3,317 dung beetles from 12 different restoration sites of varying ages (2 – 17 years) and compared them with 4 reference rainforest sites and 4 degraded pasture sites within the Wet Tropics of Australia. Species diversity metrics, community structure and functional diversity metrics of dung beetles were examined, along with important ecosystem functions that they mediate (secondary seed dispersal, dung removal and soil excavation).

The findings reveal that replanting of native tree species to previously deforested areas can recover faunal communities and ecosystem functions in a relatively short period of time (< 20 years). Most strikingly, however, the study demonstrated that the traditional species-based view of diversity is insufficient when exploring the relationship between diversity and functioning and predicting the response of ecosystem functions to restoration. The findings show that functional diversity measures, which define the diversity and abundance distribution of traits within a community, are more accurate predictors of functional recovery than species-based metrics.

Conservation implications

“Functional diversity captures differences in species’ morphology, life-history traits and ecological niches, which affect community reassembly processes and subsequent changes to ecosystem function. Traditional taxonomic indices do not capture these complexities and so could potentially misjudge the true response of biodiversity and functioning to land-use change, disturbance and ecological restoration” said lead author Mia Derhé of Lancaster University Environment Centre.

“We provide clear evidence that species-based measures of diversity are insufficient predictors of ecosystem functioning in the context of forest restoration. We therefore recommend that scientists and practitioners incorporate functional trait information and measures of ecological functions when evaluating the efficacy of restoration practices. This is particularly important, since effective assessment of ecological restoration projects is critical in justifying the use of restoration in natural resource management as well as improving best practice.”