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Sci Total Environ. 2016 Apr 1;548-549:390-401. doi: 10.1016/j.scitotenv.2015.12.137. Epub 2016 Jan 21.

Evaluating the trade-off between food and timber resulting from the conversion of Miombo forests to agricultural land in Angola using multi-temporal Landsat data.

Author information

1
University of Trier, Department of Environmental Remote Sensing and Geoinformatics, Behringstr. 21, 54286 Trier, Germany. Electronic address: schneibel.anne@uni-trier.de.
2
University of Trier, Department of Environmental Remote Sensing and Geoinformatics, Behringstr. 21, 54286 Trier, Germany. Electronic address: stellmes@uni-trier.de.
3
University of Trier, Department of Environmental Remote Sensing and Geoinformatics, Behringstr. 21, 54286 Trier, Germany. Electronic address: roeder@uni-trier.de.
4
University of Hamburg, Department of Biodiversity, Evolution and Ecology of Plants, Biocentre Klein Flottbek and Botanical Garden, Ohnhorststr. 18, 22609 Hamburg, Germany. Electronic address: manfred.finckh@uni-hamburg.de.
5
University of Hamburg, Department of Biodiversity, Evolution and Ecology of Plants, Biocentre Klein Flottbek and Botanical Garden, Ohnhorststr. 18, 22609 Hamburg, Germany. Electronic address: rasmus.revermann@botanik.uni-hamburg.de.
6
University of Trier, Department of Environmental Remote Sensing and Geoinformatics, Behringstr. 21, 54286 Trier, Germany. Electronic address: frantz@uni-trier.de.
7
University of Trier, Department of Environmental Remote Sensing and Geoinformatics, Behringstr. 21, 54286 Trier, Germany. Electronic address: hillj@uni-trier.de.

Abstract

The repopulation of abandoned areas in Angola after 27years of civil war led to a fast and extensive expansion of agricultural fields to meet the rising food demand. Yet, the increase in crop production at the expense of natural resources carries an inherent potential for conflicts since the demand for timber and wood extraction are also supposed to rise. We use the concept of ecosystem services to evaluate the trade-off between food and woody biomass. Our study area is located in central Angola, in the highlands of the upper Okavango catchment. We used Landsat data (spatial resolution: 30×30m) with a bi-temporal and multi-seasonal change detection approach for five time steps between 1989 and 2013 to estimate the conversion area from woodland to agriculture. Overall accuracy is 95%, user's accuracy varies from 89-95% and producer's accuracy ranges between 92-99%. To quantify the trade-off between woody biomass and the amount of food, this information was combined with indicator values and we furthermore assessed biomass regrowth on fallows. Our results reveal a constant rise in agricultural expansion from 1989-2013 with the mean annual deforestation rate increasing from roughly 5300ha up to about 12,000ha. Overall, 5.6% of the forested areas were converted to agriculture, whereas the FAO states a national deforestation rate for Angola of 5% from 1990-2010 (FAO, 2010). In the last time step 961,000t per year of woodland were cleared to potentially produce 1240t per year of maize. Current global agro-economical projections forecast increasing pressure on tropical dry forests from large-scale agriculture schemes (Gasparri et al., 2015; Searchinger and Heimlich, 2015). Our study underlines the importance of considering subsistence-related change processes, which may contribute significantly to negative effects associated with deforestation and degradation of these forest ecosystems.

KEYWORDS:

Agricultural expansion; Earth observation; Ecosystem services; Fallow regeneration; Multi-temporal analysis; Trade-off analysis

PMID:
26803737
DOI:
10.1016/j.scitotenv.2015.12.137
[Indexed for MEDLINE]

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