Reconstructing Long Term High Andean Forest Dynamics Using Historical Aerial Imagery: A Case Study in Colombia

Grischa Brokamp,Thomas Borsch,Mariasole Calbi,Nicola Clerici

doi:10.3390/f11080788

Grischa Brokamp, Thomas Borsch + Show 2 more

Open Access

https://doi.org/10.3390/f11080788

Copy DOI

Abstract

High Andean forests are biodiversity hotspots that also play key roles in the provisioning of vital ecosystem services for neighboring cities. In past centuries, the hinterland of Andean fast-growing cities often experienced a dramatic decline in forested areas, but there are reports that forest cover has been recovering recently. We analyzed aerial imagery spanning the years 1940 to 2007 from nine administrative localities in the Eastern Andean Cordillera of Colombia in order to elucidate precise patterns of forest vegetation change. To this aim, we performed image object-based classification by means of texture analysis and image segmentation. We then derived connectivity metrics to investigate whether forest cover trajectories showed an increase or decrease in fragmentation and landscape degradation. We observed a forest cover recovery in all the examined localities, except one. In general, forest recovery was accompanied by an increase in core habitat areas. The time scale of the positive trends identified partially coincides with the creation of protected areas in the region, which very likely furthered the recovery of forest patches. This study unveils the long-term dynamics of peri-urban high Andean forest cover, providing valuable information on historical vegetation changes in a highly dynamic landscape.

Highlights

Landscape change is the result of a broad variety of human activities with various effects on ecosystems, which depends on the nature and intensity of these activities [1,2]
Edge width was set to five meters, which we considered to be an adequate threshold in our particular study system, to distinguish between the fragment edge and core areas
Even though overall accuracy (OA), user accuracy (UA) and producer accuracy (PA) values for classes T, G and B generally fulfilled a minimum threshold of goodness, some omission errors are noticeable for the PA values for class B in some of the aerial scenes

Summary

Introduction

Landscape change is the result of a broad variety of human activities with various effects on ecosystems, which depends on the nature and intensity of these activities [1,2]. Land cover change does interfere with the structure and functioning of ecosystems, and affects the interactions with the atmosphere, contributing to local and global climate change [3,4]. In this context, habitat fragmentation modifies the availability of resources by creating artificial patch edges and by altering the degree of isolation of patches [5,6]. Landscape fragmentation poses severe threats to the native tree flora [11] and induces higher individual mortality [12] and extinction rates either at the species level [13] or at the population level [14,15].

Objectives

Methods

Discussion

Conclusion