How good do forests recover from anthropogenic disturbances?

Since ages, humans are relying on forests, as a source for fire wood, furniture or food. According to the Global Forest Resources Assessment in 2010, the earth is covered with around 1.4 billion hectares of primary forests, which is roughly 1.5 times the size of the US. On the other hand, there are at least 3.6 billion hectares of secondary forests, which are characterized by logging and (re-)cultivation, for example. More than two third of the forests we are having on earth right now are therefore not native and had experienced any form of human activities and disturbance.

The ability of forests to recover is determined by their biodiversity. The more diverse an ecosystem, the better can the function of a lost species be replaced by another species, which has a similar role in the system. Therefore, the amount of species that can be replaced or recovered after human’s intervening, is crucial for the recovery of the ecosystem in whole.

Recent research on secondary forest ecosystems in China shows that the woody plant richness of secondary forests is close to fully recovered, compared to the biodiversity of primary forests in China. The recovery ratios ranged between 85 and 103%, depending on the region (see figure 3). The authors  argue that the main reason for these impressive recovering rates are the Chinese Natural Forest Protection Program and the Nature Reserves Construction Program, which had at the same time great impact on the quality and the area of secondary forests.

Furthermore, the authors discuss the heterogeneity in recovering rates between the various regions. They found out that the richness recovery varied greatly between forest types (forests with only one, dominant (coniferous) tree species vs. broad-leaf or mixed forests) and may also be influenced by factors like soil fertility (abiotic) or distance to a nearby primary forest with a high biodiversity (biotic).

Last but not least they could refute statistics, which argue that the woody plant richness could recover (nearly) entirely within 20 years after clear cutting. The authors rather identified a recovery peak after 21-40 years and another between 61-80 years (see figure 4).

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