Browsing by Author "Phalan, B."
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Item Biodiversity in a forest-agriculture mosaic - The changing face of West African rainforests(Biological Conservation, 2010-10) Norris, K.; Asase, A.; Collen, B.; Gockowksi, J.; Mason, J.; Phalan, B.; Wade, A.The biodiversity of West African rainforests is globally significant but poorly described, little understood in terms of its functional significance, and under threat from forest loss and degradation. Estimates suggest that about 10 million ha of forest may have been lost in the 20th Century, and around 80% of the original forest area is now an agriculture-forest mosaic. These highly modified forests provide food, fuel, fibre and a range of ecosystem services for over 200 million people. As a consequence, the future of biodiversity in the region is intimately linked with the lives and livelihoods of local people. The available evidence suggests that forest loss and degradation has been caused primarily by agricultural expansion, sometimes facilitated by other human activities such as wood extraction. This expansion is a response to the demand generated by a growing and increasingly urbanised human population, but has been exacerbated by small increases in crop yields over recent decades. We synthesize and review our state of knowledge on the value of human-modified habitats for forest biodiversity in the region. Data on biodiversity are patchy, but we show that across plant, invertebrate and vertebrate groups, there is a significant loss of forest species as tree cover is reduced and vegetation structure simplified. Agricultural expansion clearly causes significant local biodiversity loss. We argue that replicated landscape-scale studies are now needed that describe changes across a range of biodiversity groups (above and below ground) in relation to land-use and landscape context to address knowledge gaps and biases. Such descriptive studies need to be complemented by a deeper understanding of the causes of species turnover patterns, together with work on the consequences of biodiversity loss for ecosystem function and services. Biodiversity conservation in the region is becoming increasingly embedded within a more multi-functional view of agriculture-forest mosaics that attempts to recognise and value the range of services provided by tree cover and other land-uses. This relatively new perspective has the potential, at least in principle, to re-shape the drivers of land-use change because tree cover can generate additional revenue through carbon trading or certification schemes. It will become clearer over the coming decades whether this potential can be realised, but the implications for biodiversity conservation in the region are potentially profound. The socio-economic processes that have driven forest loss and degradation in West Africa are having an increasing impact on the relatively undisturbed rainforest of the Congo Basin. We conclude by pointing out that while West African forest landscapes are a potent reminder of what might happen in Central Africa in the near future, they also provide insights for developing policies and practice that might avoid comparable levels of forest loss and degradation. © 2010 Elsevier Ltd.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