Globally, the fragmentation of forests, which is the decay of large forest areas into smaller, isolated forest islands, is constantly progressing with numerous negative effects like the loss of biodiversity as well as increased carbon degradation and emissions to the atmosphere. Estimating the current state of global forest fragmentation is necessary to understand and project how forest fragmentation will develop in the future. Remote sensing allows for the quantification of global deforestation with high spatial resolution and enabled us to achieve substantial advances in the analysis of the continental-wide fragmentation of tropical forests. Based on high-resolution maps of forest cover, we calculated the number and size of connected forest fragments in three continents across the tropical belt. To understand the observed fragmentation structures and to project future developments of forest fragmentation, we developed a dynamic fragmentation model which is simulated and analyzed for each tropical region per continent under different future deforestation scenarios.
Results/Conclusions
We identified roughly 130 million forest fragments in three continents that show surprisingly similar power law size and perimeter distributions as well as fractal dimensions. Power law distributions have been observed in many natural phenomena like wild fires and earth quakes. Here, the principles of percolation theory provide one explanation for the observed patterns and suggest that forest fragmentation is close to the critical point of percolation. Our dynamic fragmentation model supports this hypothesis and reveals that the observed patterns do not only emerge from random deforestation (as described by percolation theory) but also from a wide range of deforestation and forest recovery regimes. Predictions of our model outline that additional forest loss will strongly increase the total number of forest fragments (maximum by factor 33 over 50 years while fragment sizes decrease) – a consequence that can be only partly mitigated by reforestation and forest protection.