An Amazonian rainforest and its fragments as a laboratory of global change

Laurance et al (2017), Biol. Rev. doi: 10.1111/brv.12343

We synthesize findings from one of the world’s largest and longest-running experimental investigations, the Biological Dynamics of Forest Fragments Project (BDFFP). Spanning an area of ∼1000 km2 in central Amazonia, the BDFFP was initially designed to evaluate the effects of fragment area on rainforest biodiversity and ecological processes. However, over its 38-year history to date the project has far transcended its original mission, and now focuses more broadly on landscape dynamics, forest regeneration, regional- and global-change phenomena, and their potential interactions and implications for Amazonian forest conservation. The project has yielded a wealth of insights into the ecological and environmental changes in fragmented forests. For instance, many rainforest species are naturally rare and hence are either missing entirely from many fragments or so sparsely represented as to have little chance of long-term survival. Additionally, edge effects are a prominent driver of fragment dynamics, strongly affecting forest microclimate, tree mortality, carbon storage and a diversity of fauna. 

Even within our controlled study area, the landscape has been highly dynamic: for example, the matrix of vegetation surrounding fragments  has changed  markedly over time, succeeding from large  cattle  pastures or forest clearcuts to secondary regrowth  forest. This, in turn,  has influenced the dynamics  of plant  and animal  communities and their trajectories of change over time. In general, fauna and flora have responded differently to fragmentation:  the most locally extinction-prone  animal  species are those that  have both large  area  requirements and low tolerance of  the  modified  habitats  surrounding  fragments,  whereas  the  most  vulnerable plants  are  those  that  respond poorly to edge effects or chronic forest disturbances, and that rely on vulnerable animals for seed dispersal or pollination. 

Relative  to intact  forests, most fragments are hyperdynamic,  with unstable or fluctuating populations of species in response to a variety  of external vicissitudes. Rare weather events such as droughts, windstorms and floods have had strong impacts on fragments and left lasting legacies of change. Both forest fragments and the intact forests in our study area appear to be influenced by larger-scale  environmental drivers operating at regional or global scales. These drivers are apparently increasing forest productivity and have led to concerted, widespread increases in forest dynamics and plant growth,  shifts in tree-community composition, and increases in liana (woody vine) abundance.

Such large-scale drivers are likely to interact synergistically with habitat fragmentation, exacerbating its effects for some species and ecological phenomena. Hence, the impacts of fragmentation on Amazonian biodiversity and ecosystem processes appear to be a consequence not only of local site features but also of broader changes occurring at landscape, regional and even global scales.

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith