Woody vegetation dynamics in the tropical and subtropical Andes from 2001 to 2014: Satellite image interpretation and expert validation

Abstract

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 for the period 2001–2014. 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 statistically significant (p < 0.05) 14 year linear trend (positive—forest gain, negative—forest loss) within each hexagon. Of the 1,308 hexagons with significant trends, 36.6% (n = 479) lost forests and 63.4% (n = 829) gained forests. We estimated an overall net gain of ~500,000 ha in woody vegetation. Forest loss dominated the 1,000–1,499 m elevation zone and forest gain dominated above 1,500 m. The most important transitions were forest loss at lower elevations for pastures and croplands, 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 shade coffee, pine, or eucalypt plantations. In addition, after controlling for elevation and country, forest gain was associated with a decline in the rural population. Although we document an overall gain in forest cover, the recent reversal of forest gains in Colombia demonstrates that these coupled natural‐human systems are highly dynamic and there is an urgent need of a regional real‐time land‐use, biodiversity, and ecosystem services monitoring network.

Elevation and latitude drives structure and tree species composition in Andean forests: Results from a large-scale plot network

“…dendrometer bands) in all the permanent forest plots of the Network; 6) detecting situations that are locally important; 7) promoting comparative research for monitoring the impacts of anthropogenic activities across the region, including the dynamics of invasive species (i.e. the case of Ligustrum lucidum in Argentina) [79], or primary/secondary succession as a result of volcanism, forest fires, hurricanes, or land use change (abandonment of agricultural and livestock lands); 8) exploring in detail the association between changes in permanent plots and changes in remotely sensed descriptors of functioning (e.g., NDVI) [80], promoting joint research to develop high resolution models of climate change for the Andean region, and descriptions of land use change [12].…”

“…Andean forests face a high risk of degradation as a result of climate change [9,10] and land use change [11,12] due to human population growth [7] and migration [12,13,14,15], and a combination of these factors [15]. Changes in Andean forest cover includes both forest regrowth mostly frequent above 2000 m asl and deforestation that often concentrates below 1000 m asl [12].…”

“…Andean forests face a high risk of degradation as a result of climate change [9,10] and land use change [11,12] due to human population growth [7] and migration [12,13,14,15], and a combination of these factors [15]. Changes in Andean forest cover includes both forest regrowth mostly frequent above 2000 m asl and deforestation that often concentrates below 1000 m asl [12]. Some Andean countries have already lost~50-60% (~550.500 km 2 total) of their cloud forests [16] due to historical and ongoing land use changes, linked to the expansion of the agricultural frontier, increase in extension of cattle ranching areas for pastures, and other economic activities such as mining, road constructions among others [17,18,19].…”

Hydroclimate of the Andes Part I: Main Climatic Features

“…The complexity of the topography and the relative low density/short period of the meteorological network over the Andes have been an inconvenience for a proper characterization of the main atmospheric circulation patterns and their relationships with the main hydroclimatic features, including the spatio-temporal characterization of precipitation over the whole of the Andes chain. Sustainable development in the Andes is currently menaced by changes ranging from local and regional (land use and deforestation; e.g., Nobre et al, 2016;Aide et al, 2019) to global (climate change; Magrín et al, 2014), which in turn would affect its climate and water resources, from glaciers retreat (Rabatel et al, 2013) to water supply and ecosystem services (Vuille et al, 2018).…”

Current and future suitable habitat areas for Nasuella olivacea (Gray, 1865) in Colombia and Ecuador and analysis of its distribution across different land uses

“…In the period 2001-2014, at 1,500-4,000 m, a ligneous vegetation gain of 130,000 and 190,000 ha has occurred in Ecuador and Colombia, respectively (Aide et al 2019), which is a hopeful factor for the conservation of the Mountain Coati.…”