A Contemporary Assessment of Change in Humid Tropical Forests

Abstract

In recent decades the rate and geographic extent of land-use and land-cover change has increased throughout the world's humid tropical forests. The pan-tropical geography of forest change is a challenge to assess, and improved estimates of the human footprint in the tropics are critical to understanding potential changes in biodiversity. We combined recently published and new satellite observations, along with images from Google Earth and a literature review, to estimate the contemporary global extent of deforestation, selective logging, and secondary regrowth in humid tropical forests. Roughly 1.4% of the biome was deforested between 2000 and 2005. As of 2005, about half of the humid tropical forest biome contained 50% or less tree cover. Although not directly comparable to deforestation, geographic estimates of selective logging indicate that at least 20% of the humid tropical forest biome was undergoing some level of timber harvesting between 2000 and 2005. Forest recovery estimates are even less certain, but a compilation of available reports suggests that at least 1.2% of the humid tropical forest biome was in some stage of long-term secondary regrowth in 2000. Nearly 70% of the regrowth reports indicate forest regeneration in hilly, upland, and mountainous environments considered marginal for large-scale agriculture and ranching. Our estimates of the human footprint are conservative because they do not resolve very small-scale deforestation, low-intensity logging, and unreported secondary regrowth, nor do they incorporate other impacts on tropical forest ecosystems, such as fire and hunting. Our results highlight the enormous geographic extent of forest change throughout the humid tropics and the considerable limitations of the science and technology available for such a synthesis.

Targeted carbon conservation at national scales with high-resolution monitoring

“…Accounting for 26 ± 9% of the ACD variation, woody canopy cover is foremost a function of precipitation (14), which decreases along a steep gradient from the wet Amazon to the dry Pacific side of the Andes. In closed-canopy forests, decreases in woody canopy cover are tightly coupled to deforestation (15). Elevation also has a large overarching effect (18 ± 6%) on ACD (SI Appendix, Fig.…”

Responses of Soil Fungi to Logging and Oil Palm Agriculture in Southeast Asian Tropical Forests

“…Tropical forests contain more than two-thirds of all terrestrial plant and animal species [1][2][3], but long-term prospects for their survival are uncertain, as more than half of the original extent of these forests has already been degraded by human land-use change and other perturbations [4]. Agricultural expansion continues to be the main driver of tropical deforestation [5] with more than one third of the global terrestrial land area currently under cultivation [6].…”

“…Agricultural expansion continues to be the main driver of tropical deforestation [5] with more than one third of the global terrestrial land area currently under cultivation [6]. Selective logging is the next largest contributor to tropical forest degradation and recent surveys show that more than 20 % of tropical forests are being actively logged [4]. The cumulative result of these activities is that the majority of tropical forest landscapes now exist in various stages of disturbance and recovery, with primary forests now representing a small fraction of the total remaining habitat [7,8].…”

Slow recovery of a secondary tropical forest in Southeast Asia

“…Secondary forests now constitute a substantial portion of forest area in the tropics due to widespread and ongoing anthropogenic disturbances and conversions (Asner et al, 2009;Chazdon, 2003). These perturbations take many forms including swidden agriculture, semi-permanent agriculture, grazing and logging.…”