Abstract
Abstract. High-Andean wetlands from northern Chile are considered worldwide biodiversity hot spots, however, they are subdued to high anthropic pressure. The monitoring of state variables, such as vegetation, allows to know the ecosystem’s global condition, which could be assessed by the analysis of spectral vegetation indices. The main goal of this paper was to detect changes in the high-Andean wetland vegetation, with remote sensing tools, to focalize surveillance efforts and the use of resources from environmental agencies. NDVI time series were constructed spanning from 1986 to 2019 based on Landsat data, which were analyzed based on the vegetation change detection using BFAST Monitor method. Detected changes were categorized to highlight certain types of changes that were considered more relevant. Wetlands were separated in two rankings (A and B) based on detected changes and territorial context. From 5,622 wetlands, 81 were categorized into group A and 510 into group B. One affected wetland was used as study case to assess the method’s efficiency, being able to detect changes and assign a relative importance to the case. It is shown that the proposed method has the capacity to detect vegetation degradation processes in high-Andean wetlands and could improve in the efficiency and effectiveness of the environmental agencies control labors over these ecosystems.
Highlights
High-Andean wetlands located in northern Chile have a high ecological value due to the high species richness that can be found in these ecosystems because of the high spatial heterogeneity, being considered biodiversity hotspots (Ahumada, Faúndez, 2009)
3.3.1 Generation of vegetation index: Time series for vegetation monitoring are based on the Normalized Difference Vegetation Index (NDVI) (Rouse et al, 1974), which is used as a proxy for vegetation vigor and/or cover and has been proven to be precise in the estimation of vegetation cover for arid zones (Barati et al, 2011)
With the aim to detect the wetlands that experienced the most relevant changes and help to eliminate false change detections due to the own methods limitations, a pixel-level categorization was done based on the magnitude and slope of the historic period and monitoring period linear trends
Summary
High-Andean wetlands located in northern Chile have a high ecological value due to the high species richness that can be found in these ecosystems because of the high spatial heterogeneity, being considered biodiversity hotspots (Ahumada, Faúndez, 2009) They provide ecosystem services which are very important for local communities, such as hydrological cycle regulation and food supply (RamsarMMA, 2015, ten Brink et al, 2013). Their azonal distribution is associated to temporally or permanently saturated soil strata due to local hydrogeological conditions This makes them highly susceptible to changes in hydrological regimes of the systems that feed them, which are considered one of the main drivers of change (Ahumada et al, 2011; Ahumada, Faúndez, 2009). They are only analyzed based on specific inspections caused by complaints and to a lesser extent by scheduled inspections
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