Friday, November 5, 2010

The effects of forest fragmentation after 30 years

ResearchBlogging.orgLarge-scale alteration of nature landscapes has had profound implications for biological diversity. The single biggest contributor to the current extinction crisis is the wholesale destruction of habitats. As habitats are destroyed, formerly contiguous landscapes become fragmented into smaller patches. But what exactly the effects of fragmentation are, independent of habitat destruction, is not always so clear (e.g., Simberloff 2000. What do we really know about fragmentation? Texas Journal of Science 52: S5-S22).

The biological dynamics of forest fragments project (BDFFP) in the Amazon, was started in 1979 and created 11 tropical forest patches ranging from 1 to 100 ha in size. The dynamics of these fragments have been consistently monitored and compared to plots in intact forest. This experiment represents the world's largest, longest-running fragmentation experiment and has told us more about fragmentation then any other study system. In a recent publication by William Laurance and many colleagues involved in this project, they summarize 30 years of data and show how fragmentation affects ecological patterns and processes.
Fragments turn out to be very dynamic and defined by change, compared to interior plots. They have higher tree mortality and are much more susceptible to weather events such as storms or droughts. The effects are especially pronounced at the edges of these fragments. The edge community face high mortality but also have higher tree density. Faunal communities in fragments and especially near edges are depauperate.

One interesting aspect highlighted by this 30 years of research is that the edge effects are strongly influenced by what is happening around the fragments. The fragment edge effects are sensitive to the composition of the inter-patch matrix, giving managers the opportunity to influence fragment diversity and health by managing the matrix in ways that support fragments. Because of over 30 years of perseverance of the researchers involved, this experiment give scientists, managers and policy-makers information to help manage an increasingly fragmented world and to find ways to reduce to negative impacts of habitat destruction.

Laurance, W., Camargo, J., Luizão, R., Laurance, S., Pimm, S., Bruna, E., Stouffer, P., Bruce Williamson, G., Benítez-Malvido, J., & Vasconcelos, H. (2010). The fate of Amazonian forest fragments: A 32-year investigation Biological Conservation DOI: 10.1016/j.biocon.2010.09.021

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