Browsing by Author "Arcilla, N."
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Item Severe declines of understory birds follow illegal logging in Upper Guinea forests of Ghana, West Africa(Biological Conservation, 2015-08) Arcilla, N.; Holbech, L.H.; O'Donnell, S.We investigated how legal logging history and recent illegal logging affected forest bird community structure in Ghana. Ghanaian forests belong to West Africa’s highly fragmented Upper Guinea rain forests, part of a global priority “biodiversity hotspot” under intense pressure from anthropogenic degradation. Between 1995 and 2010, officially-reported legal logging intensities increased up to ∼600%, while illegal logging, which now accounts for 80% of timber extraction in Ghana, has driven logging intensities to ∼6 times greater than the maximum sustainable rate. We collected data in 2008–2010 and used a comparable dataset collected in 1993–1995 to assess impacts of recent logging on understory bird communities in large forest fragments (100–524 km2) in southwest Ghana. Forest understory bird species abundance declined by >50% during this period. Species richness also showed declining trends. Whereas analysis based on data collected in 1993–1995 estimated a partial post-logging recovery of the understory bird community at that time, data from 2008–2010 showed no indication of post-logging recovery, likely due to ongoing illegal logging following intensive legal logging operations. Forest generalist species and sallying insectivores declined significantly in logged compared to unlogged forests. These severe declines of Upper Guinea forest understory birds indicate the rapidly deteriorating conservation status of a biodiversity hotspot and could signal collapsing ecosystem processes. Immediate conservation actions are urgently required to protect surviving forest fragments from further degradation and avian declines.Item Uncontrolled hunting and habitat degradation decimate and extirpate forest hornbills in Ghana, West Africa(Elsevier Ltd, 2018) Holbech, L.H.; Annorbah, N.N.D.; Phalan, B.; Arcilla, N.Tropical forests are on the front lines of the current global extinction crisis. Species with restricted habitat requirements and slow reproductive rates, such as the spectacular hornbills (Bucerotidae) of the Paleotropics, are particularly vulnerable. We present the first long-term quantitative population assessment of nine forest hornbill species in Ghana, part of the Upper Guinea forest biodiversity hotspot in West Africa. From 1990 to 2009, hornbill encounter rates declined with 32–88% across eight species found in the region. Seven separate surveys between 1990 and 2014 indicated declines in at least six of eight species detected, with large-bodied species hardest hit. Depleted remnant populations of large hornbills mainly persist in two large and relatively well-protected wildlife reserves, Ankasa Resource Reserve and Kakum National Park. Contrastingly, the five largest species of the nine hornbills known to Bia Biosphere Reserve, one of Ghana's few forest wildlife reserves, apparently vanished completely since the 1990s, mainly due to uncontrolled hunting. Similarly, several large hornbills have disappeared from forest reserves where hunting is widespread. We conclude that uncontrolled hunting is the major driver of the recent drastic declines and population extirpations of large hornbills, while reductions in small insectivorous species may be related to extensive fragmentation and habitat disturbances of the Ghanaian forest biome. We call for urgent conservation action to prevent further declines and impending extirpations of forest hornbills and other wildlife in West Africa. © 2018 Elsevier Ltd