Global patterns of tropical forest fragmentation

Satellite data and modelling reveal that tropical forest fragments have similar size distributions across continents, and that forest fragmentation is close to a critical point, beyond which fragment numbers will strongly increase. Forest fragmentation patterns Agriculture, logging and urban growth have caused unprecedented losses of tropical forest in the past few decades. Franziska Taubert and colleagues examine patterns of tropical forest fragmentation using high-resolution satellite data. They identify 130 million forest fragments across three continental regions, which each have size frequency distributions that are similar, being described by power laws with almost identical exponents. The principles of percolation theory provide one explanation for the observed patterns, and suggest that forest fragmentation is close to a critical threshold, beyond which fragmentation can be expected to accelerate strongly. Numerical modelling supports this hypothesis, suggesting that additional forest loss will strongly increase the total number of forest fragments over the next 50 years. However, the simulations also suggest that reforestation and reductions in deforestation can mitigate this projected increase in fragmentation. Remote sensing enables the quantification of tropical deforestation with high spatial resolution 1 , 2 . This in-depth mapping has led to substantial advances in the analysis of continent-wide fragmentation of tropical forests 1 , 2 , 3 , 4 . Here we identified approximately 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 5 , 6 , 7 have been observed in many natural phenomena 8 , 9 such as wildfires, landslides and earthquakes. The principles of percolation theory 7 , 10 , 11 provide one explanation for the observed patterns, and suggest that forest fragmentation is close to the critical point of percolation; simulation modelling also supports this hypothesis. The observed patterns emerge not only from random deforestation, which can be described by percolation theory 10 , 11 , but also from a wide range of deforestation and forest-recovery regimes. Our models predict that additional forest loss will result in a large increase in the total number of forest fragments—at maximum by a factor of 33 over 50 years—as well as a decrease in their size, and that these consequences could be partly mitigated by reforestati