Restoration of Degraded Tropical Forest Landscapes

Background

The rapid loss and degradation of tropical forests has been one of the defining features of the 20th century, with an estimated 350 million ha deforested and another 500 million ha (primary and secondary forest) in degraded status. There have been three major responses to this process: expanding protected areas; improving agricultural productivity on cultivated and abandoned lands; and plantation-style reforestation using a very limited number of species. These methods have proven unsuccessful in slowing the rate of deforestation or providing adequately for livelihoods.

Research goals & methods

This review article discusses methods of reforestation in recent use that may be more effective in reforestation and forest management. Enrichment planting in recently cleared sites to bring back species without a local seedbank has proven effective in some cases. However, in other sites, especially with major or long-term degradation, thresholds are crossed that make reforestation difficult, often in the case of erosion or conversion to grassland.

Restoration plantings have also been widely used, either of a low diversity of pioneer species or a much greater diversity of early- and later-successional species. The latter approach generally carries a much higher cost, especially with inadequately developed PES markets, and is rarely suitable for subsequent timber harvesting.

Conclusions & takeaways

Further development of diverse mosaic plantings and further development of PES models will aid in the ambition and effectiveness of reforestation efforts. The biggest challenge, however, will be moving restoration from a site-based activity to a landscape activity. It is at the landscape level that restoration can be used to complement the existing protected area network, and it is at the landscape level that biodiversity restoration and production (and hence poverty alleviation) can be most easily made complementary.