Browsing by Author "Sanchun, A."
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Item Land cover dynamics following a deforestation ban in northern Costa Rica(IOP Science, 2013) Fagan, M. E.; DeFries, R. S.; Sesnie, S. E.; Arroyo, J. P.; Walker, W.; Soto, C.; Chazdon+, R. L.; Sanchun, A.Forest protection policies potentially reduce deforestation and re-direct agricultural expansion to already-cleared areas. Using satellite imagery, we assessed whether deforestation for conversion to pasture and cropland decreased in the lowlands of northern Costa Rica following the 1996 ban on forest clearing, despite a tripling of area under pineapple cultivation in the last decade. We observed that following the ban, mature forest loss decreased from 2.2% to 1.2% per year, and the proportion of pineapple and other export-oriented cropland derived from mature forest declined from 16.4% to 1.9%. The post-ban expansion of pineapples and other crops largely replaced pasture, exotic and native tree plantations, and secondary forests. Overall, there was a small net gain in forest cover due to a shifting mosaic of regrowth and clearing in pastures, but cropland expansion decreased reforestation rates. We conclude that forest protection efforts in northern Costa Rica have likely slowed mature forest loss and succeeded in re-directing expansion of cropland to areas outside mature forest. Our results suggest that deforestation bans may protect mature forests better than older forest regrowth and may restrict clearing for large-scale crops more effectively than clearing for pasture.Item Tracking deforestation and tree plantation expansion in a Costa Rican biological corridor using a Landsat time series(2012) Fagan, Matthew E.; Sesnie, S. E.; Arroyo, J.P.; Walker, W.; Soto, C.; Chazdon, R.L.; Sanchun, A.; Small, C.; DeFries, R.S.We evaluated forest policies and programs to reestablish connectivity in a fragmented tropical landscape spanning approximately 2500 km2: the San Juan-La Selva Biological Corridor (SJLSBC) in northern Costa Rica. National forest conservation programs have concentrated payments for environmental services (PES) within corridors to establish tree plantations and protect forests on private land; the corridor program was instituted in 1996 as part of a Forest Law that also banned deforestation country-wide. Despite the innovative nature of this program, agricultural pressures on the SJLSBC may have impeded its implementation. To effectively and efficiently monitor forest protection laws and conservation incentives, new remote sensing-based methods are needed that can overcome difficulties in distinguishing between tropical tree plantations, mature forests, and forest regrowth using low-cost moderate- (10- 100 m) to coarse-resolution (100-300 m) satellite sensors. The objective of this study was to accurately map changes in the area of these three forest types and agriculture in northern Costa Rica using Landsat imagery spanning a 25 year period (1986-2011). We used a combined hierarchical approach that integrates temporal image-object segmentation and machine-learning classification techniques to track forest cover change and distinguish between spectrally-similar forest types. Results indicate that, during the 15 years since its creation, the deforestation ban has been effective in protecting mature lowland forests. The area of secondary forest declined however, indicating that agricultural pressures on easily-clearable land are increasing. Tree plantations expanded rapidly over the time period analyzed, although the rate of increase has slowed. Agricultural intensification was notable during the period of study; pineapple cultivation expanded dramatically into former pastures and threatens to bisect the corridor zone by expanding down major river valleys. Although the SJLSBC program and national deforestation ban have protected mature forest and promoted tree plantation establishment, the expansion of intensive agriculture and long-term decline in secondary forest may lead to a semi- permanent loss of forest connectivity in this developing region.