A Diachronic Analysis of a Changing Landscape on the Duero River Borderlands of Spain and Portugal Combining Remote Sensing and Ethnographic Approaches

Kyle P Hearn,Jesús Álvarez-Mozos

doi:10.3390/su132413962

Abstract

The Arribes del Duero region spans the border of both Spain and Portugal along the Duero River. On both sides of the border, the region boasts unique human-influenced ecosystems. The borderland landscape is dotted with numerous villages that have a history of maintaining and managing an agrosilvopastoral use of the land. Unfortunately, the region in recent decades has suffered from massive outmigration, resulting in significant rural abandonment. Consequently, the once-maintained landscape is evolving into a more homogenous vegetative one, resulting in a greater propensity for wildfires. This study utilizes an interdisciplinary, integrated approach of “bottom up” ethnography and “top down” remote sensing data from Landsat imagery, to characterize and document the diachronic vegetative changes on the landscape, as they are perceived by stakeholders and satellite spectral analysis. In both countries, stakeholders perceived the current changes and threats facing the landscape. Remote sensing analysis revealed an increase in forest cover throughout the region, and more advanced, drastic change on the Spanish side of the study area marked by wildfire and a rapidly declining population. Understanding the evolution and history of this rural landscape can provide more effective management and its sustainability.

Highlights

The analysis focused on visible (RGB), near infrared (NIR) and short-wave infrared (SWIR) spectral bands, with a spatial resolution of 30 m
Sincethe themid-20th mid-20thcentury, century,aanew new story storyisisbeing beingtold: told:aastory storyofofpopulation populationdecline, decline,ofofrural ruralabandonment, abandonment,and andofofchanging changing perceptions perceptionsofofthis thislandscape landscapefrom fromstakeholders stakeholderswho whonow nowvalue valuethe thelandscape landscapeless lessfor forits its traditional land use but instead for its ecological singularity and, to a lesser degree, the traditional land use but instead for its ecological singularity and, to a lesser degree, the socioeconomic benefits that can be reaped from this ecological distinction and its evolving land cover
After implementing an initial time series of vegetation indices for the region, we developed a quantifiably accurate and effective landscape classification with stable training sites, which was used to demonstrate diachronic land cover change over a 34-year period

Summary

Introduction

In the European Union, Spain and Portugal are among the most affected in this demographic shift, in terms of rural agricultural land abandonment. According to the European Commission, by 2030 Spain is expected to lose the highest level of agricultural land due to land abandonment in the European Union, at over 1 million hectares. Causes of rural land abandonment vary among demographic [4], political [5], socioeconomic, and ecological shifts [6,7]. Rural abandonment has undoubtedly led to more wild vegetative growth, in some regions it has had positive effects as a means of carbon sequestration, the improvement of water quality, or the prevention of soil erosion [8,9]. For the Mediterranean region, it has often led a decrease in biodiversity [10]

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