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Understanding the dynamics of natural ecosystems in highly transformed landscapes is key to the design of regional development plans that are more sustainable and otherwise enhance conservation initiatives. We analyzed secondary forest and shrubland dynamics over 30 years in a densely populated area of the Colombian Andes using satellite and biophysical data. We performed a land-cover change analysis, assessed landscape fragmentation, and applied regression models to evaluate the effects of environmental and geographical correlates with the observed forest transitions. Forest cover area increased during the 30 year-span, due mostly to forest regrowth in areas marginal for agriculture, especially during the first half of the study period. However, a high dynamic of both forest regrowth and clearing near urban centers and roads was observed. Soil fertility turned out to be a key correlate of both forest recovery and deforestation. Secondary forests, <30 years old represent the most fragmented component. Our findings reflect the complexity of the processes occurring in highly transformed and densely populated regions. Overall, this study provides elements for a better understanding of the factors driving land cover change near large urban areas, and raises new iideas for further research.proportion of the world's biodiversity and have experienced unprecedented rates of deforestation [17]. Yet many other tropical ecosystems such as the Brazilian Cerrado, Atlantic forests, Chilean matorrals, and tropical dry forests, have lost proportionately more natural vegetation cover than the forests of the Amazon Basin. The deforestation of these ecosystems adds up to 3.6 million km 2 [18]. Indeed, between 2000 and 2012, 58% of the deforested area in South America took place outside the Amazonian region [19].Among the most diverse and threatened tropical ecosystems are those hosted by the Andean mountain ranges, considered a major biodiversity hotspot [20]. The Northern Andes in Colombia are particularly vulnerable to land cover change, as they own an extraordinary level of species diversity and endemism [11,21]. Unfortunately, Andean forests have been subject to substantial forest loss, as they have been densely settled and exploited since the Spanish colonization [22]. Current drivers of landscape change are cropping and cattle grazing, and to a lesser extent, to mining. In remote areas, illicit crops are also an important cause of deforestation and forest fragmentation [23][24][25]. As a result, only 31% of the Andean natural forests were left at the beginning of the century [26,27].During the last decade, Andean ecosystems have experienced considerable vegetation recovery thanks to land abandonment resulting from spontaneous or forced population migration. As an example, in the 2001-2010 period, about 65% of the total national woody net gain occurred in different Andean montane forest ecoregions in South America [28]. Secondary forests provide multiple ecosystem services and serve as critical reservoirs for thousands of ter...

Periurban forests are key to offsetting anthropogenic carbon emissions, but they are under constant threat from urbanization. In particular, secondary Neotropical forest types in Andean periurban areas have a high potential to store carbon, but are currently poorly characterized. To address this lack of information, we developed a method to estimate periurban aboveground biomass (AGB)-a proxy for multiple ecosystem services-of secondary Andean forests near Bogotá, Colombia, based on very high resolution (VHR) GeoEye-1, Pleiades-1A imagery and field-measured plot data. Specifically, we tested a series of different pre-processing workflows to derive six vegetation indices that were regressed against in situ estimates of AGB. Overall, the coupling of linear models and the Ratio Vegetation Index produced the most satisfactory results. Atmospheric and topographic correction proved to be key in improving model fit, especially in high aerosol and rugged terrain such as the Andes. Methods and findings provide baseline AGB and carbon stock information for little studied periurban Andean secondary forests. The methodological approach can also be used for integrating limited forest monitoring plot AGB data with very high resolution imagery for cost-effective modelling of ecosystem service provision from forests, monitoring reforestation and forest cover change, and for carbon offset assessments.

En Colombia existen actualmente 1.391 áreas protegidas y tanto en su interior como en sus fronteras (zonas de amortiguación) se desarrollan muchas actividades humanas. El estudiante doctoral de la Facultad de Ciencias Naturales Kristian Rubiano mapeó 51 áreas protegidas para determinar las trayectorias de cambio en el uso de la tierra. Los resultados, que fueron presentados en la 58a Reunión Anual de la Asociación para la Biología Tropical y Conservación (ATBC), mostraron que las áreas protegidas están cumpliendo parcialmente su rol de conservar los ecosistemas.