Woody vegetation dynamics in the Andes from 2001 to 2014: the impacts of land use change and climate.
AIDE, M.; GRAU, H.R.; GRAESSER, J.; ANDRADE NUÑEZ, M.J.; ARÁOZ, E.; BARROS, A.P.; CAMPOS-CERQUEIRA, M. ; CHACÓN MORENO, E.
GLOBAL CHANGE BIOLOGY
WILEY-BLACKWELL PUBLISHING, INC
Lugar: Londres; Año: 2019
The interactions between climate and land use change are dictating the distribution of flora and fauna and reshuffling biotic community composition around the world. Tropical mountains are particularly sensitive because they often have a high human population density, a long history of agriculture, range-restricted species, and high-beta diversity due to a steep elevation gradient. Here we evaluated the change in distribution of woody vegetation in the tropical Andes of South America above 1000 m for the period 2001 to 2014. For the analyses we created annual land cover/land use maps using MODIS satellite data at 250-m pixel resolution, calculated the cover of woody vegetation (trees and shrubs) in 9,274 hexagons of 115.47 km2, and then determined if there was a significant 14-year linear trend (positive ? forest gain, negative ? forest loss) within each hexagon. Of the 1,358 hexagons with significant trends, 36.7% (n=498) lost forests and 63.3% (n=860) gained forests. We estimated an overall net gain of ~500,000 ha in woody vegetation. Forest loss dominated the 1000-1499 m elevation zone and forest gain dominated above 1500 m. The most important transitions were forest loss at lower elevations for pastures and agriculture, forest gain in abandoned pastures and cropland in mid elevation areas, and shrub encroachment into highland grasslands. Expert validation confirmed the observed trends, but some areas of apparent forest gain were associated with new coffee, pine, or eucalypt plantations. The interactions among climate change, demographic dynamics, economic activity as reflected by nighttime lights, and land tenure conflicts underlie many of the observed patterns. Although we document an overall gain in forest cover, the recent reversal of forest gains in Colombia demonstrates that these coupled natural-human system are highly dynamic and there is an urgent need of a regional real-time land use, biodiversity, and ecosystem services monitoring network.