Space-time detection of deforestation, forest degradation and regeneration in montane forests of Eastern Tanzania
Naturally isolated montane forests in East Africa are hotspots of biodiversity, often characterised by high species endemism, and are fundamental contributors to water services. However, they are located in areas highly suitable for agriculture, making them a prime target for agricultural activities...
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| Format: | Article |
| Language: | English |
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Elsevier
2020-06-01
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| Series: | International Journal of Applied Earth Observations and Geoinformation |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S0303243419310529 |
| _version_ | 1811228457587179520 |
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| author | Eliakim Hamunyela Patric Brandt Deo Shirima Ha Thi Thanh Do Martin Herold Rosa Maria Roman-Cuesta |
| author_facet | Eliakim Hamunyela Patric Brandt Deo Shirima Ha Thi Thanh Do Martin Herold Rosa Maria Roman-Cuesta |
| author_sort | Eliakim Hamunyela |
| collection | DOAJ |
| description | Naturally isolated montane forests in East Africa are hotspots of biodiversity, often characterised by high species endemism, and are fundamental contributors to water services. However, they are located in areas highly suitable for agriculture, making them a prime target for agricultural activities. The Eastern Arc Mountains (EAM) in Eastern Tanzania are within the target regions for agricultural development under the Southern Agricultural Growth Corridor of Tanzania (SAGCOT). However, forest monitoring initiatives that track long-term forest dynamics and the ecological impact of current agricultural development policies on forests, are lacking. Here, we use the STEF (Space-Time Extremes and Features) algorithm and Landsat time series to track forest disturbances (deforestation and degradation) and forest gains (regeneration) as spatio-temporal events over seventeen years (2001–2017) in the montane forests of the Mvomero District in Tanzania. We found that 27 % (∼ 20 487 ha) of montane forests were disturbed between 2001 and 2017, mainly led by deforestation (70 %). Small-scale crop farms with maize, banana, and cassava crops, were the most planted on deforested areas. Most disturbances occurred at lower elevation (lowland montane), but there was an increasing shift to higher elevations in recent years (2011–2017). Forest disturbances exclusively occurred at small spatial scales, a pattern similar to other forest montane landscapes in Africa, which lowers detection capabilities in global forest loss products. Our locally calibrated and validated deforestation map (Producer's accuracy = 80 %; User’s accuracy = 78 %) shows a gross underestimation of forest cover loss (>10 000 ha) by global forest loss products in these mountainous forest landscapes. Overall, we found few areas undergoing forest regeneration, with only 9 % of the disturbed forest regenerating over 17 years. Long-term conversion to cropland prevented regeneration in the lowlands, with regeneration mainly happening at higher elevations. However, the shift of deforestation and forest degradation to higher elevations may challenge high elevation regeneration trends, leaving the remaining blocks of montane forest in the Mvomero District at a risk of degradation and disappearance. Without effective forest conservation measures, market-driven agricultural development is likely to trigger an expansion of cropland at the expense of forests to meet the increased demand for the agricultural products promoted, with negative impact on biodiversity, carbon sequestration and water services. |
| first_indexed | 2024-04-12T09:58:07Z |
| format | Article |
| id | doaj.art-f1fe202c84b943aa96a23ac3b0d951d8 |
| institution | Directory Open Access Journal |
| issn | 1569-8432 |
| language | English |
| last_indexed | 2024-04-12T09:58:07Z |
| publishDate | 2020-06-01 |
| publisher | Elsevier |
| record_format | Article |
| series | International Journal of Applied Earth Observations and Geoinformation |
| spelling | doaj.art-f1fe202c84b943aa96a23ac3b0d951d82022-12-22T03:37:38ZengElsevierInternational Journal of Applied Earth Observations and Geoinformation1569-84322020-06-0188102063Space-time detection of deforestation, forest degradation and regeneration in montane forests of Eastern TanzaniaEliakim Hamunyela0Patric Brandt1Deo Shirima2Ha Thi Thanh Do3Martin Herold4Rosa Maria Roman-Cuesta5University of Namibia, Faculty of Humanity and Social Sciences, Private Bag 13301, Windhoek, Namibia; Corresponding author.Center for International Forestry Research (CIFOR), P.O. Box 30677, 00100, Nairobi, Kenya; Wageningen University & Research, Laboratory of Geo-Information Science and Remote Sensing, Droevendaalsesteg 3, PB Wageningen, 6708, the NetherlandsSokoine University of Agriculture, Department of Ecosystems and Conservation, TanzaniaCenter for International Forestry Research (CIFOR), P.O. Box 30677, 00100, Nairobi, Kenya; Forest Research Centre, Southern Cross University, Lismore, NSW 2480, AustraliaWageningen University & Research, Laboratory of Geo-Information Science and Remote Sensing, Droevendaalsesteg 3, PB Wageningen, 6708, the NetherlandsCenter for International Forestry Research (CIFOR), P.O. Box 30677, 00100, Nairobi, Kenya; Wageningen University & Research, Laboratory of Geo-Information Science and Remote Sensing, Droevendaalsesteg 3, PB Wageningen, 6708, the NetherlandsNaturally isolated montane forests in East Africa are hotspots of biodiversity, often characterised by high species endemism, and are fundamental contributors to water services. However, they are located in areas highly suitable for agriculture, making them a prime target for agricultural activities. The Eastern Arc Mountains (EAM) in Eastern Tanzania are within the target regions for agricultural development under the Southern Agricultural Growth Corridor of Tanzania (SAGCOT). However, forest monitoring initiatives that track long-term forest dynamics and the ecological impact of current agricultural development policies on forests, are lacking. Here, we use the STEF (Space-Time Extremes and Features) algorithm and Landsat time series to track forest disturbances (deforestation and degradation) and forest gains (regeneration) as spatio-temporal events over seventeen years (2001–2017) in the montane forests of the Mvomero District in Tanzania. We found that 27 % (∼ 20 487 ha) of montane forests were disturbed between 2001 and 2017, mainly led by deforestation (70 %). Small-scale crop farms with maize, banana, and cassava crops, were the most planted on deforested areas. Most disturbances occurred at lower elevation (lowland montane), but there was an increasing shift to higher elevations in recent years (2011–2017). Forest disturbances exclusively occurred at small spatial scales, a pattern similar to other forest montane landscapes in Africa, which lowers detection capabilities in global forest loss products. Our locally calibrated and validated deforestation map (Producer's accuracy = 80 %; User’s accuracy = 78 %) shows a gross underestimation of forest cover loss (>10 000 ha) by global forest loss products in these mountainous forest landscapes. Overall, we found few areas undergoing forest regeneration, with only 9 % of the disturbed forest regenerating over 17 years. Long-term conversion to cropland prevented regeneration in the lowlands, with regeneration mainly happening at higher elevations. However, the shift of deforestation and forest degradation to higher elevations may challenge high elevation regeneration trends, leaving the remaining blocks of montane forest in the Mvomero District at a risk of degradation and disappearance. Without effective forest conservation measures, market-driven agricultural development is likely to trigger an expansion of cropland at the expense of forests to meet the increased demand for the agricultural products promoted, with negative impact on biodiversity, carbon sequestration and water services.http://www.sciencedirect.com/science/article/pii/S0303243419310529Forest lossRegenerationTanzaniaMontane forestSAGCOT |
| spellingShingle | Eliakim Hamunyela Patric Brandt Deo Shirima Ha Thi Thanh Do Martin Herold Rosa Maria Roman-Cuesta Space-time detection of deforestation, forest degradation and regeneration in montane forests of Eastern Tanzania International Journal of Applied Earth Observations and Geoinformation Forest loss Regeneration Tanzania Montane forest SAGCOT |
| title | Space-time detection of deforestation, forest degradation and regeneration in montane forests of Eastern Tanzania |
| title_full | Space-time detection of deforestation, forest degradation and regeneration in montane forests of Eastern Tanzania |
| title_fullStr | Space-time detection of deforestation, forest degradation and regeneration in montane forests of Eastern Tanzania |
| title_full_unstemmed | Space-time detection of deforestation, forest degradation and regeneration in montane forests of Eastern Tanzania |
| title_short | Space-time detection of deforestation, forest degradation and regeneration in montane forests of Eastern Tanzania |
| title_sort | space time detection of deforestation forest degradation and regeneration in montane forests of eastern tanzania |
| topic | Forest loss Regeneration Tanzania Montane forest SAGCOT |
| url | http://www.sciencedirect.com/science/article/pii/S0303243419310529 |
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