Publication Date:
2016-09-06
Description:
Prosopis juliflora is a drought-tolerant fast-growing tree species originating from South and Central America with a high invasion potential in arid and semi-arid areas in Africa. It was introduced in Somaliland in the 1980s, and is reported to have spread vigorously since. Despite being recognised as a serious issue in the country, the actual scale of the problem is unknown. In this study, we mapped the species in a study area that includes the capital, Hargeisa, using Landsat 8 satellite imagery. During a field campaign in 2015 we collected canopy-level spectral signatures of P. juliflora and native trees, to analyse the potential use of spectral data in discriminating the invasive species. P. juliflor a was found to be generally distinguishable because of its greater vigour during the dry season. We tested the accuracy of the Random Forest classifier and different classification set-ups, varying the spatial resolution (original 30 m vs. pan-sharpened 15 m) and image acquisition dates (during the wet season, the dry season and a combination of the two). Best overall accuracy (84%) was achieved using pan-sharpened data from the two seasons. About 30 years since its introduction, the invasive species was detected in 9% of the total investigated area with highest occurrence in the proximity of human settlements and along seasonal water courses.
Print ISSN:
1085-3278
Electronic ISSN:
1099-145X
Topics:
Geography
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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