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Uncontrolled hunting and habitat degradation decimate and extirpate forest hornbills in Ghana, West Africa
Abstract
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.
... In urban-forest mosaics of KwaZulu-Natal, occupancy modelling showed that large trees had a positive influence on Trumpeter Hornbill (Bycanistes bucinator) presence, while human presence negatively influenced its detection probability (Chibesa and Downs 2017). Holbech et al. (2018) identified two small-bodied hornbill species in Ghana that are not subject to hunting pressure that have seen population declines, suggesting limited resilience to forest degradation (Holbech et al. 2018). In Ghana, while the versatile West African Pied Hornbill (Lophoceros semifasciatus) persists in fragmented forests, this fragmentation was thought to be a factor driving significant population declines (Holbech et al. 2018). ...
... In urban-forest mosaics of KwaZulu-Natal, occupancy modelling showed that large trees had a positive influence on Trumpeter Hornbill (Bycanistes bucinator) presence, while human presence negatively influenced its detection probability (Chibesa and Downs 2017). Holbech et al. (2018) identified two small-bodied hornbill species in Ghana that are not subject to hunting pressure that have seen population declines, suggesting limited resilience to forest degradation (Holbech et al. 2018). In Ghana, while the versatile West African Pied Hornbill (Lophoceros semifasciatus) persists in fragmented forests, this fragmentation was thought to be a factor driving significant population declines (Holbech et al. 2018). ...
... Holbech et al. (2018) identified two small-bodied hornbill species in Ghana that are not subject to hunting pressure that have seen population declines, suggesting limited resilience to forest degradation (Holbech et al. 2018). In Ghana, while the versatile West African Pied Hornbill (Lophoceros semifasciatus) persists in fragmented forests, this fragmentation was thought to be a factor driving significant population declines (Holbech et al. 2018). ...
Background: Seven out of ten hornbill species in the Philippines are threatened with extinction. Among these is the endangered Visayan Hornbill ( Penelopides panini ), found on the islands of Panay and Negros. Threatened by habitat loss and hunting, its population size is thought to have declined from 1800 individuals 20 years ago to less than 1000. However, a recent study on Negros estimated 3564 individuals across three core forest blocks. This study aims to quantify the Visayan Hornbill population size in and around the Northwest Panay Peninsula Natural Park (NWPPNP) on Panay, the largest contiguous low-elevation forest landscape remaining across its range, and its broad habitat associations across a gradient of environmental degradation.
Methods: Hornbills were surveyed using 10-min distance sampling point counts ( n = 367) along transects (average length 1.1 km). Environmental variables were recorded along transects, while habitat was classified into primary forest, secondary forest, plantation, or open habitat. Distance software was used to estimate population densities stratified by habitat, with the overall population estimate taken as a mean of habitat density estimates weighted by habitat area. Using generalized linear mixed models, hornbill occurrence was modelled using combinations of nine environmental variables as main and two-way fixed effects.
Results: Surveys covered 204.4 km ² of the 374.8 km ² Northwest Panay Peninsula. Hornbills were not recorded in plantations or open habitats. Hornbill density was significantly higher in primary forest (17.8 individuals/km ² ± 26.9% CV) than in secondary forest (3.7 individuals/km ² ± 33.2% CV; z = 15.212, P < 0.001). The overall population estimate for the NWPPNP and environs is 2109 individuals, and 2673 individuals for the entire Northwest Panay Peninsula. Hornbill presence was best explained by a model including distance from the Park boundary alongside five interaction effects and transect as a random effect. Distance, and the interaction between distance and medium-sized trees were significant predictors of hornbill presence.
Conclusions: Our study evidences the habitat preference of the Visayan Hornbill, highlights the importance of the NWPPNP for the species’ conservation, and provides strong evidence for re-assessing the global population size.
... Hunting threatens wildlife conservation by driving wildlife species to extirpation (Annorbah et al., 2016;Holbecha et al., 2018). Harrison (2011) described how hunters have deprived tropical forests of wildlife species and the ecological services they provide. ...
... In this study, it is not surprising to observe the predominant use of fire by the farmer-hunters since fire is commonly used for clearing of the land. The use of fire in hunting tends to be indiscriminately used, causing huge tracts of forest cover to be burnt, destroying wildlife habitats, and driving extirpation in some species (Holbecha et al., 2018). ...
Hunting is a prevalent threat to wildlife conservation. Understanding hunting behavior and attitudes toward wildlife are instrumental to effective wildlife conservation. The concept of wildlife value orientation (WVO) presents an opportunity to understand how people value and want wildlife to be managed. Little attention has been given to how demographics influence wildlife value orientations with the hunting context. This article assessed hunting behavior and demographic dimensions of WVO of farmer-hunters. Using a survey, 140 respondents were sampled using convenience sampling. Differences in the important WVOs based on demographics were determined using independent-samples t-test and one-way between-groups ANOVA. Results indicated that farmers-hunters generally exhibit more of mutual belief orientation than domination orientation. There was a significant difference in value orientation based on education, indicating that education can influence the opportunity to actively engage them to support wildlife conservation.
... large hornbills, Sierra Leone Prinia Schistolais leontica and Timneh Parrot Psittacus timneh (cf. Annorbah et al. 2016, Holbech et al. 2018. Surveys should target sites with recent records, IBAs where the species has been reported in the past, and other areas with apparently suitable conditions. ...
... MEA (2005) has also noted the importance of catchment protection, non-timber forest products, and hunting in rural areas. However, hunting can be environmentally degrading, especially where hunters intentionally or unintentionally set forest on fire with the objective of increasing their capture of wild animals (Holbech et al., 2018). ...
Since the 1990s, integrated catchment management (ICM) has been promoted as a holistic and integrated approach to water resources management. However, there is evidence to show that the costs and benefits associated with ICM are often inequitably distributed. This study investigates impacts of the implementation of catchment strategies on four rural communities and the coping mechanisms available to residents to cope with concomitant socioeconomic hardships within the Densu River basin, Ghana. The study relies on data collected through reviewing regulatory and policy documents, interviews, observations, and a household survey of 327 respondents. The results show that the implementation of the catchment strategies has negatively impacted the economies of all communities leading to local resistance. Increasing unemployment, decreasing incomes, and decreasing sales are generating increasing crime rates, out migration, and changing gender roles with additional burden on women. What compounds the problem are that socioeconomic interventions and coping mechanisms have failed to make any significant impact. We argue that for effective ICM, proportional representation of local people on catchment committees should be central in order to incorporate a thorough understanding of the local socioeconomic issues and integrating those issues into the implementation process; otherwise catchment strategies risk disproportionately impacting rural communities.
... Abedi-Lartey (1998) saw evidence of heavy hunting and noted that the forest reserve was easily accessible, under intense pressure from local communities and itinerant illegal mineral prospectors, and that old and new farms cultivating oil palm ran right up to the reserve boundary. A survey by Gatti (2010) covered 50 km (36 hours and 30 minutes) and yet failed to see this species, but he noted that an ornithologist, Ben Phalan, had heard a group calling (see Holbech et al. 2018), that a captive juvenile had been confiscated in a nearby village, and that his team had seen them prior to his survey. However, an unpublished survey carried out in September/October 2011, organised by the NGO West African Primate Conservation Action (WAPCA) and led by David Osei, did record white-naped mangabeys in the reserve (WAPCA, WD & CRC, 2011). ...
The white-naped mangabey Cercocebus lunulatus is severely threatened by logging, mining, and hunting. In the last decade, wild populations have been confirmed in just three forested areas in Ghana and a handful of sites in neighboring Côte d’Ivoire and Burkina Faso. Sightings of this species were recently reported in a fourth area in Ghana, the Cape Three Points Forest Reserve, a forest patch in western Ghana, 60 km from the nearest recorded wild population, which is in the Ankasa Conservation Area. We deployed 14 camera traps across 21 different locations throughout the reserve, with the intention of confirming the presence of this species. Images of the white-naped mangabey were captured at four locations, consolidating recent evidence for a fourth sub-population of this species in Ghana and providing only the second-ever photograph of a wild member of this species in the country. We observed evidence of numerous illegal anthropogenic activities in the reserve, which threaten these mangabeys, and we make recommendations for the protection of the reserve, essential for the conservation of this highly endangered species.
The marabou stork ( Leptoptilos crumenifer ) is widespread and generally abundant in East and Southern Africa, but recent research has found range loss indicative of a population decline in West Africa in recent decades. In the absence of population data, we conducted an in‐depth review of the status of the marabou in the region using a plethora of sources together comprising the largest database on the occurrence of the species. Despite caveats and coarseness of the assessment, we estimate the range loss at 52% in West Africa, including extirpation of approximately 64% of known nesting colonies since 2000. The resulting fragmentation has left a metapopulation of likely no more than 100 breeding pairs in The Gambia and Benin and an unknown number of breeders in Cameroon. Knowledge gaps about marabou population ecology in West Africa are significant and prevent an empirical assessment of regional extinction probability. Therefore, we recommend immediate field surveys, especially for breeding colonies, and research into threats and population dynamics. We also recommend the West African metapopulation be listed as regionally critically endangered and that a working group be formed comprising stakeholders from across the region to aid in assessing threats and implementing research and conservation action.
In Africa, overhunting of tropical wildlife for food remains an intractable issue. Donors and governments remain committed to invest in efforts to both conserve and allow the sustainable use of wildlife. Four principal barriers need to be overcome: 1) communities are not motivated to conserve wildlife long-term because they have no formal rights to benefit from wildlife, or to exclude others from taking it on their land; 2) multi-species harvests, typical of bushmeat hunting scenarios, place large-bodied species at risk of extinction; 3) wildlife production cannot expand, in the same way that livestock farming can, to meet the expected growth in consumer demand; and 4) wildlife habitat is lost through conversion to agriculture, housing, transportation networks, and extractive industries. In this review, we examine the actors involved in the use of wildlife as food and discuss the possible solutions required to address urban and rural bushmeat consumption. Interventions must tackle use and conservation of wildlife through the application of context-relevant interventions in a variety of geographies across Africa. That said, for any bushmeat solution to work there needs to be concurrent and comparable investment in strengthening the effectiveness of protected area management and enforcement of wildlife conservation laws.
The heavily traded Grey Parrot Psittacus erithacus is believed to have undergone rapid population decline, yet there are almost no quantitative data on abundance changes over time from anywhere within its huge range. We reviewed the species' historical abundance across Ghana, undertook targeted searches during 3- to 5-day visits to 42 100-km(2) cells across the country's forest zone, repeated counts at 22 parrot roosts first performed two decades ago and gauged around 900 people's perceptions of the decline and its causes. In over 150days of fieldwork, just 32 groups (maximum group size=12) were recorded in 10 cells. Encounter rates averaged 0.15 individuals per hour of targeted search, around 15 times lower than those recorded in the early 1990s. No active roosts were found, and only 18 individuals were recorded in three roost areas that each harboured 700-1200 birds two decades ago. Interviewees stressed the importance of very tall trees of commercially important species such as Terminalia superba and Ceiba pentandra for nesting and roosting, and believed that the felling of large trees on farmland (42% of responses) and trapping for trade (37%) were the two main causes of decline. Ghana has lost 90-99% of its Grey Parrots since 1992, a time when the population had presumably already been seriously reduced by two decades of extremely heavy trade. There is no evidence that, away from one or two localities, declines are less severe anywhere else within the West African range of P.erithacus, or across the entire range of the recently split Timneh Parrot Psittacus timneh.
The avifauna of the moist evergreen Bia Forest in southwest Ghana was studied for six months using standardised repeated line transect walks. Three sites were selected for comparative studies; two logged areas with respectively two and 14 years of regeneration, and an unlogged site serving as control. Logging intensity was assessed quantitatively, and the vegetation structure was classified according to vertical strata coverage. Over 9,600 bird presence records were made, involving over 130 species. Species richness, diversity and relative abundance of birds were highest in recently logged forest whereas virgin and old logged forest sites were similar regarding these parameters. Species similarity was high (75-88 per cent) and guild compositions varied little between any of the sites. Out of 98 species with sufficient statistical data for comparative site testing, only 15 per cent were adversely affected on long term, whereas 34 per cent appeared to benefit from logging, leaving 51 per cent unaffected on long term. Several nationally rare species seemed to persist well in logged areas, and only three rare species were under-represented in both early and late regenerating forest, including one IUCN Red List species restricted to Upper Guinea forest biome. Low extraction levels of 1-2 trees per ha in Bia had only moderate and short-term negative impacts on theavifauna, hence the Bia forestry model may serve as general regional guidelines for ecologically sustainable selective logging, which seems compatible with bird conservation objectives. These findings, dating back almost 25 years, however, contrast the current development of forestry practises and timber exploitation in Ghana, in which extraction levels often exceeds 5-6 trees per ha, providing only limited recovery of forest birds. The experiences from Bia, are also discussed in comparative terms with similar studies in West, Central and East Africa, and tentative recommendations on sustainable logging with respect to Upper Guinea forest bird conservation objectives are proposed.
Conservation is at a critical juncture because of the increase in poaching which threatens key species. Poaching is a major public concern, as indicated by the rises in rhino and elephant poaching, the United for Wildlife Initiative and the London Declaration, signed by 46 countries in February 2014. This is accompanied by an increasing calls for a more forceful response, especially to tackle the involvement of organized crime in wildlife trafficking. However, there is a risk that this will be counter-productive. Further, such calls are based on a series of assumptions which are worthy of greater scrutiny. First, calls for militarization are based on the idea that poverty drives poaching. Yet, poaching and trafficking are changing because of the shifting dynamics of poverty in supply countries, coupled with changing patterns of wealth in consumer markets. Second, the ways increases in poaching are being linked to global security threats, notably from Al Shabaab are poorly evidenced and yet circulate in powerful policy circles. There is a risk that militarization will place more heavily armed rangers in the centre of some of the most complex regional conflicts in the world (such as the Horn of Africa and Central Africa/Sahel region).
Tropical forest conservation and restoration require an understanding of the movements and habitat preferences of important seed dispersers. With forests now being altered at an unprecedented rate, avian frugivores are becoming increasingly vital for forest regeneration. Seed movement, however, is highly dependent on the behavioral characteristics of their dispersers. Here, we examined the movements, habitat preferences, and range sizes of two African frugivores: the Black-casqued (Ceratogymna atrata) and the White-thighed (Bycanistes albotibialis) Hornbill, in the lowland rain forests of southern Cameroon. Using satellite transmitters, we tracked eight hornbills for 3 yr to characterize their movements and relate them to environmental landscape features. Hornbill movements differed significantly, with B. albotibialis ranging over larger areas (mean = 20,274 ha) than C. atrata (mean = 5604 ha), and females of both species covering over 15 times the area of males. Evidence suggests that movements are irruptive during particular periods, perhaps driven by low resource availability. In addition, hornbills often returned to the same localities within a year, although movements were not characterized as migratory. Both species displayed significant differences in habitat preference, with B. albotibialis utilizing disturbed habitat more frequently than C. atrata (t = -22.04, P = 2.2 × 10-16). Major roads were found to act as barriers for C. atrata, but not for B. albotibialis. The ability of both hornbill species to move large distances suggests hornbills will play a vital role in the maintenance and regeneration of rain forests in Central Africa as forest fragmentation increases and terrestrial vertebrates decline in numbers.
The commercial bushmeat trade threatens numerous species in the forests of West and Central Africa. Hunters shoot and trap animals, which are transported to rural and urban markets for sale. Village-based surveys of hunter offtake and surveys of bushmeat markets have shown that mammals and reptiles are affected most, followed by birds. However, hunters also consume some animals in forest camps and these may have been overlooked in surveys that have focused on bushmeat extracted from the forest. A number of studies have used indirect methods, such as hunter diaries, to quantify this additional offtake but results can be difficult to verify. We examined discarded animal remains at 13 semi-permanent hunting camps in the Ebo Forest, Cameroon, over 272 days. Twenty-one species were identified from 49 carcasses, of which birds constituted 55%, mammals 43% and other taxa 2%. The mammals identified were typical of those recorded in previous bushmeat studies but we recorded several species of birds rarely recorded elsewhere. Offtake of bird species increased with mean body mass. We extrapolated our results to the 34 known hunting camps in the Ebo Forest and estimated that a minimum of 97 birds are hunted annually in a catchment area of c. 479 km
2
. We conclude that some bird species may be hunted more frequently than previous research suggests and this has important conservation implications for larger-bodied species such as raptors and hornbills.
The African lion has declined to <35,000 individuals occupying 25% of its historic range. The situation is most critical for the geographically isolated populations in West Africa, where the species is considered regionally endangered. Elevating their conservation significance, recent molecular studies establish the genetic distinctiveness of West and Central African lions from other extant African populations. Interventions to save West African lions are urgently required. However formulating effective conservation strategies has been hampered by a lack of data on the species' current distribution, status, and potential management deficiencies of protected areas (PAs) harboring lions. Our study synthesized available expert opinion and field data to close this knowledge gap, and formulate recommendations for the conservation of West African lions. We undertook lion surveys in 13 large (>500 km(2)) PAs and compiled evidence of lion presence/absence for a further eight PAs. All PAs were situated within Lion Conservation Units, geographical units designated as priority lion areas by wildlife experts at a regional lion conservation workshop in 2005. Lions were confirmed in only 4 PAs, and our results suggest that only 406 (273-605) lions remain in West Africa, representing <250 mature individuals. Confirmed lion range is estimated at 49,000 km(2), or 1.1% of historical range in West Africa. PAs retaining lions were larger than PAs without lions and had significantly higher management budgets. We encourage revision of lion taxonomy, to recognize the genetic distinctiveness of West African lions and highlight their potentially unique conservation value. Further, we call for listing of the lion as critically endangered in West Africa, under criterion C2a(ii) for populations with <250 mature individuals. Finally, considering the relative poverty of lion range states in West Africa, we call for urgent mobilization of investment from the international community to assist range states to increase management effectiveness of PAs retaining lions.
Arboreal frugivores, such as primates and hornbills, are important seed dis- persers for many tropical plant species, yet the degree to which they use the same resources is unknown. If primates and hornbills consume the same fruit species, they may be redundant in their roles as seed dispersers, and the loss of one of these taxa may be compensated for by the other. To examine resource use by tropical frugivores, we quantified the feeding habits of two hornbill species, Ceratogymna atrata and C. cylindricus, and five primate species, Colobus guereza, Lophocebus albigena, Cercopithecus pogonias, C. cephus, and C. nictitans, in the lowland rainforest of south-central Cameroon. Based on over 2200 feeding observations recorded between January and December 1998, we characterized the diets and estimated dietary overlap among frugivore species. Previous studies have cal- culated dietary overlap by counting the number of diet species that two animals share, often leading to inflated estimates of overlap. Our method incorporated the proportional use of diet species and fruit availability into randomization procedures, allowing a clearer as- sessment of the actual degree of overlap. This added complexity of analysis revealed that, although the diets of a hornbill and a primate species may have as many as 36 plant species in common, actual dietary overlap is low. These results suggested that there are distinct hornbill and primate feeding assemblages, with primates consuming a greater diversity of plant species and higher levels of nonfruit items like leaves and seeds. Using Correspon- dence Analysis, we also identified two primate assemblages, separated largely by degree of frugivory and folivory. In addition, we found that hornbills feed at significantly higher strata in the forest canopy and eat fruits of different colors than primates. Averaged across the year, overlap between groups (hornbill-primate) was significantly lower than combined within-group overlap (primate-primate and hornbill-hornbill), showing that primates and hornbills have dissimilar diets and are not redundant as seed dispersers. In equatorial Africa, primate populations face greater declines than hornbill populations because of hunting. It is unlikely that seed dispersal by hornbills will compensate for the loss of primates in maintaining forest structure.
International donors and private citizens have invested billions of dollars to protect biodiversity in developing nations. The most popular investments aim to encourage economic activities that indirectly protect ecosystems and species. An alternative form of investment is to pay directly for conservation outcomes, as is commonly done in high-income nations. While not a “silver bullet,” direct approaches may, in many cases, be more effective and efficient than indirect ones, and thus merit greater attention in developing nations. This article is reprinted with permission from Science, Volume 298, Issue 5599, Issue of 29 November 2002, page 1718-1719. Copyright © 2002 by The American Association for the Advancement of Science. All rights reserved. Full text available in print version of the journal. Himalayan Journal of Sciences 1(2): 81-83, 2003
Starting in 2004, a system to monitor patrol staff performance, illegal wildlife use and trends in large-mammal populations was established in nine protected areas in Ghana. The main objectives were to use monitoring feedback as the foundation for informed decisions to aid adaptive and performance management, and to identify the most important factors contributing to wildlife conservation. The competitive management system resulted in a doubling of patrol performance. As a result, in the six savannah sites, poaching was reduced to acceptable levels by the end of 2007, but in the three forest sites, poaching remained high. To reverse poaching trends in the forest required a conventional patrol effort that was 10 times higher than that in the savannah.
In Ghana, budgetary allocations for protected area management have been consistently low. To improve cost-effectiveness and performance of law enforcement, monitoring feedback was used to provide the foundation for informed management decisions. Between 2004 and 2006, a system to monitor staff performance, patrol effort, illegal wildlife use, and trends in large-mammal populations was established in seven protected areas. In two national parks, where GIS-based monitoring systems were in place, in the course of 2006, data were standardised and analysed in the same way. Encounters on patrol with illegal activities and large mammals were corrected for patrol effort and the size of the area to enable comparing encounter rates in different protected areas. In December 2005, law-enforcement performance was evaluated in six protected areas. Through dissemination of the evaluation report, the poor performance of patrol staff and high levels of illegal activity in five out of six sites entered the public domain, and created a spirit of competition between protected areas. The present evaluation showed that in the course of 2006, in the six sites evaluated, patrol performance improved by 59% on average, compared to only 11% in the two parks that were not evaluated. In the four savannah sites evaluated, poaching was reduced by 72%, but only by 17% in the two forest sites evaluated. This compares with a reduction in poaching of 33% in the two parks. Patrol data were open to several types of error. Although reliability of patrol data was checked at different hierarchical levels, the final check was at headquarters in Accra, comparing seasonal fluctuations in large-mammal encounters with those in two control areas.
In healthy forests, vertebrate frugivores move seeds from intact to degraded forests, aiding in the passive regeneration of degraded forests. Yet vertebrate frugivores are declining around the world, and little is known about the impact of this loss on regeneration of degraded areas. Here, we use a unique natural experiment to assess how complete vertebrate frugivore loss affects native seed rain in degraded forest. All native vertebrate frugivores (which were primarily avian frugivores) have been functionally extirpated from the island of Guam by the invasive brown tree snake (Boiga irregularis), whereas the nearby island of Saipan has a relatively intact vertebrate frugivore community. We captured seed rain along transects extending from intact into degraded forest and compared the species richness, density and condition of the seed rain from native bird-dispersed tree species between the two islands. Considering seeds from native bird-dispersed species, approximately 1.66 seeds landed per 26 days in each square meter of degraded forest on Saipan, whereas zero seeds landed per 26 days per square meter in degraded forest on Guam. Additionally, on Saipan, 69% of native bird-dispersed seeds in intact forest and 77% of seeds in degraded forest lacked fleshy fruit pulp, suggesting ingestion by birds, compared to 0% of all seeds on Guam. Our results show an absence of seed rain in degraded forests on Guam, correlated with the absence of birds, whereas on Saipan, frugivorous birds regularly disperse seeds into degraded forests, providing a mechanism for re-colonization by native plants. These results suggest that loss of frugivores will slow regeneration of degraded forests on Guam.
The White-breasted Guineafowl Agelastes meleagrides is one of 15 bird species endemic to the Upper Guinea Forests of West Africa. The Tate d'Ivoire probably holds one of the largest remaining populations of this species. We assessed population density in two different sectors in the southern part of Ta1, density: 32.9 ind. km National Park (encounter rate: <0.002 detections km region. Our data also suggest that past disturbance from logging does not constitute an obstacle for its persistence. The population size in Taï National Park and N'Zo Faunal Reserve should be between 42,000 and 120,000 individuals.
More than 18% of tropical rainforests are now covered by totally protected areas. If these were well protected, we could feel reasonably confident that current conservation strategies might succeed in preserving a substantial proportion of tropical biodiversity. However, in most parts of the tropics, poachers enter and leave reserves with impunity. On the basis of reports from the hunting literature, it seems likely that a majority of tropical nature reserves may already be considered empty forests—meaning that all bird and mammal species larger than approximately two kilograms—barring a few hunting-tolerant species—have either been extirpated or exist at densities well below natural levels of abundance. The disruption of ecological functions caused by the loss of symbionts further compromises the capacity of these reserves to conserve biodiversity over the long term. A substantial shift toward improving the management and enforcement of tropical protected-area networks is required.
Human activities that are likely to affect primate populations in the Kakum Conservation Area in Ghana were monitored over three years in relation to number of primates sighted over the same period. The main aim was to monitor and determine trends of illegal activities in relation to primate numbers and seasons of the year. Along the patrol route, the patrol officers enumerated all encounters with human activities associated with hunting, capturing or harming animals, and all sightings of primate groups within the visual range of the observer. These encounters were examined in terms of monthly man-days of patrol effort and distances walked (km), providing indices of encounter. In all, six primate species were encountered from 2007 to 2009: bush baby (Galagoides demidoff), Bossman potto (Perodictus potto), Lowe's monkey (Cercopithecus campbelli lowei), spot-nose monkey (Cercopithecus petaurista petaurista), olive colobus (Procolobus verus), and Geoffroy's pied colobus (Colobus vellerosus). Categories of illegal activities documented in the 360 km 2 protected area included poachers arrested, firearms confiscated, used cartridges found, gunshots heard, snares found, poacher's camps encountered, primates found killed, and skins confiscated. The indices for these illegal activities showed a decrease over the three years, while encounters with primate groups were unchanged. An expectation of differences in detection of illegal activities between the farming and non-farming seasons was not supported. The results support recommendation of consistent, high-intensity patrol efforts throughout the year by well-equipped patrol units. Résumé: Les activités humaines qui affecteront probablement des populations de primate dans la Région de Conservation Kakum au Ghana ont été contrôlées plus de trois ans par rapport au nombre de primates aperçus pendant la même période. Le but principal était de contrôler et déterminer des tendances d' activités illégales par rapport aux nombres de primate et aux saisons de l' année. Le long du trajet de patrouille, les officiers de patrouille ont énuméré toutes les rencontres avec les activités humaines associées à la chasse, le fait de capturer ou la malfaisance aux animaux et à toutes les vues de groupes de primate dans la gamme visuelle de l' observateur. Ces rencontres ont été examinées du point de vue des jours d'homme mensuels d' effort de patrouille et les distances ont marché (le km), en fournissant indices de la rencontre. En tout, on a rencontré six espèces de primate à partir de 2007 à 2009: le bébé de buisson (Galagoides demidoff), le Boss potto (Perodictus potto), le singe de Lowe (Cercopithecus campbelli lowei), le singe de nez de tache (Cercopithecus petaurista petaurista), l' olive colobus (Procolobus verus) et le pied de Geoffroy colobus (Colobus vellerosus). Les catégories d' activités illégales documentées dans la 360 région km 2 protected ont inclus des braconniers arrêtés, les armes à feu les cartouches confisquées, utilisées trouvées, les coups de feu ont entendu, les pièges trouvés, les camps de braconnier rencontrés, les primates ont trouvé tué et les peaux confisqué. L'indices pour ces activités illégales a montré une diminution au cours des trois ans, pendant que les rencontres avec les groupes de primate étaient inchangées. Une attente de différences dans la détection d' activités illégales entre l' agriculture et la non-agriculture des saisons n' a pas été soutenue. Les résultats soutiennent la recommandation de conséquents, les efforts de patrouille de haute intensité tout au long de l' année par les unités bien équipées de patrouille.
Africa is home to 23 of the world's 54 hornbill species, including the largest members of the family, the ground hornbills. None of Africa's hornbills are currently considered to be at significant risk of extinction by IUCN, and none are listed under the Convention on International Trade in Endangered Species (CITES). However, there is evidence for serious declines of African forest hornbills due to habitat loss and fragmentation, and to unsustainable exploitation for bushmeat. In addition, this paper documents a previously unreported international trade involving importation of African hornbills and their parts into the United States. In the absence of CITES reporting requirements, it is difficult to estimate the magnitude of this trade, but it appears to represent an additional threat to African hornbills, particularly large forest-dwelling species of the genera Bycanistes and Ceratogymna. Given this international trade, and other known threats to African forest-dwelling hornbills, the status of these species is in urgent need of review.
Performance and adaptive management systems were introduced in all protected areas in Ghana to stop the decline in wildlife and the further loss of biodiversity. The competitive management system resulted in an increase in the relative abundance of wildlife at seven sites where the system had been in operation for 4 years (2004–2008). We examined the relationships between wildlife-based tourism and park management, and key factors that may influence tourism. First, we scrutinized the relationship between the relative abundance of illegal activity and numbers of visitors, the relative abundance of wildlife, and road network. Poaching declined with increasing numbers of tourists that acted as a deterrent, whereas poaching increased with a higher relative abundance of wildlife. Second, we examined the relationship between the numbers of visitors and the relative abundance of wildlife, species richness, distances from Accra, regional capitals and the nearest hotel; the road network on site, and the numbers of alternative tourist attractions. Increasing numbers of alternative tourist attractions, and shorter distances to the nearest hotel attracted higher numbers of visitors. An important additional factor that influenced the flow of tourists to protected areas was the presence of unique site attractions.
The population and conservation status of crocodiles throughout West and Central Africa is poorly known and the IUCN Crocodile Specialist Group's highest priority recommendations are country status surveys and examination of potential threats. This study presents survey data and a review of the conservation status of the Nile crocodile Crocodylus niloticus, slender-snouted crocodile Mecistops cataphractus and African dwarf crocodile Osteolaemus tetraspis at 67 sites throughout Ghana and Côte d'Ivoire. No crocodiles were sighted in 31.5% of surveys but, where encountered, densities averaged 0.90 crocodiles sighted km-1. The most frequently encountered crocodile was C. niloticus (94% of sightings) with population structure highly biased to individuals < 1 year of age (41.4%). Only 14 M. cataphractus were observed. Local informants report that crocodiles were more common 10–20 years ago than at present. There is now little commercial harvest, which includes limited use in the bushmeat and traditional medicine markets, because of the crocodile's scarcity. Habitat encroachment and incidental bycatch in fishing devices appear to be the major threats. Actions needed to improve the conservation status of crocodile populations in both countries, and throughout the region, are discussed.
Comparative large-scale roadside counts (8353 km), through Burkina Faso, Mali and Niger, conducted in 1969–73, were repeated 30–35 years later with the same observer and methodology and at the same season. The transect was divided into three geographical zones and between protected and unprotected areas. All diurnal raptors were recorded (22 801 individuals), as well as large game birds. Large vultures suffered a dramatic decline (98%) outside protected areas. The Hooded Vulture Necrosyrtes monachus population also collapsed in some regions, but survived in central Burkina Faso. Conversely, their abundance index did not decrease significantly in national parks. Four eagle species decreased by 86–93% and seven were not even recorded in the later study outside protected areas; by contrast, in national parks, only three species had declined marginally. Smaller Accipitridae (kites, goshawks, buzzards) also exhibited significant declines outside but not within national parks where woodland species reached their highest densities. The Common Kestrel Falco tinnunculus, mostly European migrants, declined sharply everywhere. African falcons decreased only outside protected areas. Among Palearctic migrants, Montagu's Circus pygargus and Pallid Harriers C. macrourus decreased significantly, Short-toed Eagle Circaetus gallicus less markedly, and Marsh Harrier Circus aeruginosus and Booted Eagle Hieraaetus pennatus not at all. Similar trends had previously been documented in Cameroon. They are associated with human population growth and development, global habitat degradation and ecosystem impoverishment (woodcutting, agricultural intensification, overgrazing, desertification). Heavy use of pesticides, control of locust outbreaks and overhunting have suppressed major food sources. Vultures may suffer from a shortage of carcasses, poisoning for predator control or persecution for trade of meat and body parts. Protected areas play a prominent role in the maintenance of vulture and eagle populations, even though they currently cover less than 2% of the Sudan zone and are virtually absent in the Sahel.
We provide the first documented case of the extinction in the twentieth century of a widely recognized primate taxon. During surveys in Ghana and Côte d'Ivoire in 1993–1999, we were unable to find any surviving populations of Miss Waldron's red colobus monkey ( Procolobus badius waldroni), a primate taxon endemic to the forests of this part of West Africa. We conclude that this monkey, which at least one authority considers worthy of species status, is probably extinct. Hunting by humans appears to be the ultimate cause of the extinction. Until our surveys began, little attention had been paid to the plight of this red colobus monkey, despite its listing as endangered by the World Conservation Union. The extinction of other large animals in the Upper Guinea rainforest region is likely to follow soon unless more attention is paid to the full range of endangered forms and more resources are devoted to their rigorous protection.
Conservation of tropical forests requires an understanding of the seasonal patterns of abundance and distribution of important seed dispersers. In the forests of Central Africa, three species of hornbills in the genus Ceratogymna (Aves: Bucerotidae) provide dispersal for over 50 species of trees and lianas, yet their ecology is poorly known. We present the first empirical evidence for resource tracking and large-scale movements by two of these species, which were previously considered resident. Hornbill numbers and fruit production were estimated over a one-year period in the Dja Reserve, Cameroon. Monthly abundances of C. atrata and C. cylindricus varied four- and 12-fold, respectively, and were predicted by community fruit availability as measured by fruitfall on a 4.3 km trail. In contrast, C. fistulator abundances varied little and were not related to fruit availability. Synchronous population fluctuations in sites 22 km distant were observed for atrata and cylindricus, but not for fistulator. Together, these results indicate that atrata and cylindricus populations track fruit resources via seasonal emigrations, while the fistulator population appears to be relatively sedentary. Comparisons of hornbill densities in primary and secondary forests suggest that they are important dispersers in both habitats, and will likely play larger roles in central African forest regeneration as more vulnerable seed dispersers are removed by hunting. If large seasonal movements of hornbills turn out to be a general phenomenon, effective management of central African forest reserves will require greater emphasis on reserve connectivity and on seasonal and spatial patterns of fruit production.
Despite the fact that West African tropical forests are the most fragmented in Africa, there has been no published research on biodiversity in these fragments. To determine how forest birds respond to five factors—patch size, patch isolation, canopy density, abundance of large trees, and proximity to forest edge—in these forests, we surveyed 60 species of forest birds on 121 transects (2.5 ha each) in 35 forest fragments in the semideciduous forest zone of Ghana. Species richness per transect increased with patch size over the entire range of patch sizes observed (3–33,000 ha). The diversity of forest birds (22 species) on a single transect in a large forest patch was similar to the cumulative diversity (25 species) on all 17 transects in 13 small patches. Twenty-two of 60 species were area sensitive, 15 of which were never found in small patches. These results suggest that only large forests will conserve many species of West African forest birds. Nine species were edge sensitive, 7 of which were also area sensitive. However, forest structure near patch edges was not consistent with bird responses to canopy and tree density, suggesting that mechanisms other than microclimate or structural changes ( perhaps predation or nest parasitism) underlie the response of most species that are sensitive to both edge and area. Regression of critical patch size (the smallest patch size in which a species was detected) on logarithm of body mass (an index of home range size) for 22 area-sensitive species suggests that area-sensitive species are unlikely to occur in patches smaller than several home-range areas. Canopy density influenced 13 species (11 positively, 2 negatively), and abundance of large trees influenced 8 species (3 positively, 5 negatively). Forest birds did not respond to isolation (distance from a patch to a large forest) for isolation distances of 1–25 km, suggesting that island biogeographic mechanisms had less influence on birds than other potential mechanisms of area sensitivity. Although small patches contributed little to the conservation of forest birds—species found in small patches were well represented in large patches—small patches are probably important for supporting generalist bird species that provide ecological services in the agricultural matrix and serving as nuclei for future ecosystem recovery.Resumen: A pesar de que los bosques tropicales de África Occidental son los más fragmentados en África, no existe información publicada sobre la biodiversidad de esos fragmentos. Para determinar como responden las aves de bosque a cinco factores (tamaño del fragmento, aislamiento del fragmento, densidad del dosel, abundancia de árboles grandes y proximidad al borde bosque) en estos bosques, tomamos muestras de 60 especies a lo largo de 121 transectos (2.5 Ha cada uno) en 35 fragmentos de bosque en la zona de bosque semidecíduo en Ghana. La riqueza de especies por transecto incrementó con el tamaño del fragmento en todo el rango de tamaños de fragmento (3 a 30,000 Ha). La diversidad de aves de bosque (22 especies) a lo largo de un solo transecto fue comparable a la diversidad acumulada (25 especies) en 17 transectos en 13 fragmentos pequeños. Veintidós de 60 especies fueron sensibles al tamaño del fragmento, de las cuales 15 nunca fueron encontradas en fragmentos pequeños. Estos resultados sugieren que muchas especies de aves de bosque en África Occidental se conservarán sólo en fragmentos grandes. Nueve especies fueron sensibles al borde del bosque, de las cuales 7 también fueron sensibles al tamaño del fragmento. Sin embargo, la estructura del bosque cerca del borde de los fragmentos no se correlacionó con las respuestas de las aves a los cinco factores, lo que sugiere que en la respuesta de muchas especies sensibles tanto al borde como al área subyacen mecanismos distintos al microclima o cambios estructurales ( probablemente depredación o parasitismo de nidos). La regresión del tamaño crítico del fragmento (el fragmento más pequeño en que se detectó la especie) en el logaritmo de la masa corporal (un índice del rango de hogar) en 22 especies sensibles al área sugiere que las especies sensibles al área probablemente no ocurran en fragmentos de menor tamaño que varias áreas de rango de hogar. La densidad del dosel influyó a 13 especies (11 positivamente, 2 negativamente), y la abundancia de árboles grandes influyó a 8 especies (3 positivamente, 5 negativamente). Las aves de bosque no respondieron al aislamiento (distancia del fragmento a un bosque extenso) en distancias de 1 a 25 km, lo que sugiere que los mecanismos de biogeografía de islas tuvieron menos influencia en aves que otros mecanismos potenciales de sensibilidad al área. Aunque los fragmentos pequeños contribuyeron poco a la conservación de las aves de bosque (especies encontradas en fragmentos pequeños estuvieron bien representadas en fragmentos grandes), los fragmentos pequeños probablemente son importantes para aves generalistas que proporcionan servicios ecológicos en la matriz agrícola y funcionan como núcleos para la futura recuperación de ecosistemas.
We studied two species of Ceratogymna hornbills, the black-casqued hornbill, C. atrata, and the white-thighed hornbill, C. cylindricus, in the tropical forests of Cameroon, to understand their movement patterns and evaluate their effectiveness as seed dispersers. To estimate hornbill contribution to a particular tree species' seed shadow we combined data from movements, determined by radio-tracking, with data from seed passage trials. For 13 individuals tracked over 12 months, home range varied between 925 and 4,472 ha, a much larger area than reported for other African avian frugivores. Seed passage times ranged from 51 to 765 min, with C. atrata showing longer passage times than C. cylindricus, and larger seeds having longer gut retention times than smaller seeds. Combining these data, we estimated that seed shadows were extensive for the eight tree species examined, with approximately 80% of seeds moved more than 500 m from the parent plant. Maximum estimated dispersal distances for larger seeds were 6,919 and 3,558 m for C. atrata and C. cylindricus, respectively. The extent of hornbill seed shadows suggests that their influence in determining forest structure will likely increase as other larger mammalian dispersers are exterminated.
Global biodiversity is threatened by unsustainable exploitation for subsistence and commerce, and tropical forests are facing a hunting crisis. In Central African forests, hunting pressure has been quantified by monitoring changes in the abundance of affected species and by studying wild meat consumption, trade and hunter behaviour. However, a proportion of offtake is also discarded as bycatch or consumed by hunters when working, which can be overlooked by these methods. For example, remains of hornbills and raptors are found regularly in hunting camps but relatively few birds are consumed in households or traded in markets. Hornbill and raptor populations are sensitive to small increases in mortality because of their low intrinsic population growth rates, however, the scale and socioeconomic drivers of the cryptic hunting pressure affecting these species have not been quantified. We used direct and indirect questioning and mixed-effects models to quantify the socioeconomic predictors, scale and seasonality of illegal bird hunting and consumption in Littoral Region, Cameroon. We predicted that younger, unemployed men with low educational attainment (i.e. hunters) would consume birds more often than other demographics, and that relative offtake would be higher than expected based on results from village and market-based studies. We found that birds were primarily hunted and consumed by unemployed men during the dry season but, in contrast to expectations, we found that hunting prevalence increased with educational attainment. Within unemployed men educated to primary level (240 of 675 respondents in 19 villages), we estimated an average of 29 hornbills and eight raptors (compared with 19 pangolins) were consumed per month during the study period (Feb-Jun 2015) in a catchment of c.1135 km 2. We conclude that large forest birds face greater hunting pressure than previously recognised, and birds are a regular source of protein for men during unemployment. Offtake levels may be unsustainable for some raptors and hornbills based on life history traits but in the absence of sufficient baseline ecological and population data we recommend that a social-ecological modeling approach is used in future to quantify hunting sustainability.
Hunting is a major driver of biodiversity loss, but a systematic large-scale estimate of huntinginduced
defaunation is lacking.We synthesized 176 studies to quantify hunting-induced
declines of mammal and bird populations across the tropics. Bird and mammal abundances
declined by 58% (25 to 76%) and by 83% (72 to 90%) in hunted compared with unhunted
areas. Bird and mammal populations were depleted within 7 and 40 kilometers from hunters’
access points (roads and settlements). Additionally, hunting pressure was higher in areas with
better accessibility to major towns where wild meat could be traded. Mammal population
densities were lower outside protected areas, particularly because of commercial hunting.
Strategies to sustainablymanage wildmeat hunting in both protected and unprotected tropical
ecosystems are urgently needed to avoid further defaunation.
Elephant populations are in peril everywhere, but forest elephants in Central Africa have sustained alarming losses in the last decade [1]. Large, remote protected areas are thought to best safeguard forest elephants by supporting large populations buffered from habitat fragmentation, edge effects and human pressures. One such area, the Minkébé National Park (MNP), Gabon, was created chiefly for its reputation of harboring a large elephant population. MNP held the highest densities of elephants in Central Africa at the turn of the century, and was considered a critical sanctuary for forest elephants because of its relatively large size and isolation. We assessed population change in the park and its surroundings between 2004 and 2014. Using two independent modeling approaches, we estimated a 78–81% decline in elephant numbers over ten years — a loss of more than 25,000 elephants. While poaching occurs from within Gabon, cross-border poaching largely drove the precipitous drop in elephant numbers. With nearly 50% of forest elephants in Central Africa thought to reside in Gabon [1], their loss from the park is a considerable setback for the preservation of the species.
Agriculture is arguably the greatest threat to tropical forest species. Conservation scientists disagree over the relative importance of two opposing strategies for minimising this threat: enhancing on-farm biodiversity, through wildlife-friendly farming practices, or sparing land for nature by using high-yielding farming methods on the smallest possible area to reduce the need to convert natural habitats. Previous theoretical work shows that understanding the relationship between population density and yield for individual species is crucial for determining whether one of these strategies, or a mixed strategy, will maximise their populations for a given food production target.
In this thesis, I aim to identify what land-use strategy will permit increases in food production with least impact on species in the forest zone of Ghana. Farm-fallow mosaic landscapes with shifting cultivation and native canopy trees produced only around 15% as much food energy per hectare as the highest-yielding oil palm plantations. In farm mosaics where perennial tree crops dominate, food production and profits were higher, but did not reach those of oil palm plantations. I surveyed birds and trees in forest, farm mosaic, and oil palm plantation, and combined these data with information on yields to assess the likely consequences of plausible future scenarios of land-use change. My results provide evidence of a strong trade-off between wildlife value and agricultural yield. Species richness was high in low-yielding farming systems, but there was considerable turnover between these systems and forests, with widespread generalists replacing narrowly endemic forest-dependent species. Species most dependent on forest as a natural habitat, those with smaller global ranges and those of conservation concern showed least tolerance of habitat modification. For virtually all species, including even widespread generalists, future land-use strategies based on land sparing are likely to support higher populations of most species and minimise their risk of extinction compared to land-use strategies based on wildlife-friendly farming.
If food production is to increase in line with Ghana‘s population growth, a combination of efforts to improve forest protection and to increase yields on current farmed land is likely to achieve this at least cost to forest species. Efforts to better protect forests, which require further restrictions on human use, might be most effective if they can be closely linked to support for farmers to improve their yields. In the long term however, this strategy will only delay and not avert biodiversity loss, unless global society can limit its consumption.
Despite all the attention the problem of illegal logging has recently attracted, the empirical base remains remarkably weak in many countries including Ghana. Using both official reported figures and actual harvest figures estimated from domestic and export consumption statistics, the annual average illegal logging for the period 2000–2011 among the formal sector in Ghana is estimated at 0.78 million m³ or 104% of the legal harvest. The results indicate that illegal logging was much more prevalent in the forest reserves than outside forest reserves, and among the traditionally endangered timber species more than the lesser known timber species. The implications of these findings on forest law compliance, enforcement, and the Voluntary Partnership Agreement (VPA) between the European Community and Ghana are discussed and recommendations proffered.
Spanish
A pesar de todo el interés que ha atraído recientemente el problema de la tala ilegal, la base empírica sigue siendo notablemente escasa en muchos países, como por ejemplo Ghana. Mediante la utilización de cifras publicadas oficiales y cifras de aprovechamientos efectuados estimadas a partir de las estadísticas de consumo nacionales y de exportación, se estimó que la tala ilegal para el período 2000–2011 dentro del sector formal en Ghana fue de un promedio anual de 0,78 millones de m³, equivalente al 104% de los aprovechamientos legales. Los resultados indican que la tala ilegal es mucho más prevalente en las reservas forestales que fuera de las mismas, así como entre las especies de madera tradicionalmente en peligro en comparación con las especies maderables menos conocidas. Se discuten las implicaciones de estos resultados en el cumplimiento de la legislación forestal, su aplicación y el Acuerdo Voluntario de Asociación (AVA) entre la Unión Europea y Ghana y se ofrecen recomendaciones.
French
Malgré toute l'attention que le problème de la coupe de bois illégale a récemment attiré, la base empirique demeure singulièrement faible dans nombre de pays, Ghana inclus. En utilisant à la fois les chiffres rapportés officiellement et les chiffres de récolte réelle estimés par les statistiques de consommation domestique et à l'exportation, la coupe de bois illégale annuelle moyenne pour la période 2000–2011 dans le secteur formel du Ghana est estimée à 0.78 millions de m³, soit 104% de la récolte légale. Ces résultats indiquent que la coupe de bois illégale était bien plus dominante dans les réserves forestières qu'en dehors de ces dernières, et davantage auprès des espèces traditionnellement en danger que parmi celles moins connues. Les implications de ces découvertes sur l'observation de la loi et sa mise en application et sur l'Accord de partenariat volontaire (VPA) entre la Communauté Européenne et le Ghana sont examinées, et de recommandations sont offertes.
The introduction of nationally-managed "western"-style protected area systems in Africa often led to antagonism between government authorities and local communities, because rural communities, which were largely excluded and displaced, often resorted to unsustainable activities like encroachment for settlement, illegal hunting and farming. It is the view of most biodiversity conservationists, however, that the management of natural resources must take into consideration both the introduced "western" model and traditional or local knowledge. The study aimed at assessing the Boabeng-Fiema Monkey Sanctuary in Ghana, as an example of blending traditional and introduced wildlife conservation systems, using interviews and questionnaire to obtain information from a cross-section of inhabitants of the area. The results indicated that the dual management system in operation at present has been largely successful, as the inhabitants appear to support the mechanisms put in place to manage the Sanctuary. Policy recommendations proposed to further enhance this success are in the areas of research and monitoring, education and awareness, tourism improvement, and introduction of community incentive schemes.
Despite several decades of research on the effects of fragmentation and habitat change on biodiversity, there remain strong biases in the geographical regions and taxonomic species studied. The knowledge gaps resulting from these biases are of particular concern if the forests most threatened with modification are also those for which the effects of such change are most poorly understood. To quantify the nature and magnitude of such biases, we conducted a systematic review of the published literature on forest fragmentation in the tropics for the period 1980-2012. Studies included focused on any type of response of single species, communities, or assemblages of any taxonomic group to tropical forest fragmentation and on fragmentation-related changes to forests. Of the 853 studies we found in the SCOPUS database, 64% were conducted in the Neotropics, 13% in Asia, 10% in the Afrotropics, and 5% in Australasia. Thus, although the Afrotropics is subject to the highest rates of deforestation globally, it was the most disproportionately poorly studied biome. Significant taxonomic biases were identified. Of the taxonomic groups considered, herpetofauna was the least studied in the tropics, particularly in Africa. Research examining patterns of species distribution was by far the most common type (72%), and work focused on ecological processes (28%) was rare in all biomes, but particularly in the Afrotropics and for fauna. We suggest research efforts be directed toward less-studied biogeographic regions, particularly where the threat of forest fragmentation continues to be high. Increased research investment in the Afrotropics will be important to build knowledge of threats and inform responses in a region where almost no efforts to restore its fragmented landscapes have yet begun and forest protection is arguably most tenuous. Sesgos Biogeográficos y Taxonómicos en la Investigación de la Fragmentación de Bosques Tropicales.
Hunting in tropical forests decimates large mammals, and this may have direct and indirect effects on other trophic levels and lead to trophic cascades. We compared replicated sites of hunted and protected forests in southeastern Nigeria, with respect to community composition of primates, other mammals, birds, plant seedlings, and mature trees. We make pre- dictions regarding the community composition at the different trophic levels. In forests where large primates are rare, we hypothesize that their ecological role will not be fully compensated for by small frugivores. We apply multivariate methods to assess changes in community composition of mammals, birds, and seedlings, controlling for any differences between sites in the other groups, including mature trees. Medium and large (4–180 kg) primates were much rarer in hunted sites, while porcupine and rock hyrax increased in abundance with hunting. In contrast, the community composition of birds was similar in both types of forests. Seedling communities were significantly related to the community composition of mammals, and thus strongly affected by hunting. In protected forests primate dispersed plant seedling species dominated, whereas in hunted forests the seedling community was shifted towards one dominated by abiotically dispersed species. Tis was probably both a consequence of reduced seed dispersal by primates, and increased seed predation by rodents and hyrax. Hence we found no evidence for buffering effects on tree regeneration through functional compensation by non-hunted animals (such as birds). Our results highlight how seedling communities are changed by the complex plant–animal intera- ctions, triggered by the loss of seed dispersers. Te results predict a rarity of primate-dispersed trees in future tropical forest canopies; a forest less diverse in timber and non-timber resources.
The urgent global objective of developing sustainable tropical forestry management practices, which also target biodiversity conservation, requires rapid comparative studies that address both biogeography and logging practices. This paper examines avifaunal implications (focusing on species diversity and composition) of forest fragmentation and selective logging, by comparing 15 selected reserved forests in south-west Ghana. The regeneration time since last logging varied from 0 (logging continuing) to 21 years, with one unlogged site as control. Extraction levels ranged between 0.20 and 3.75 trees per ha (mean 0.90). Bird sampling involved understorey mist-netting and standardized line-transect walks, which respectively accumulated 8,348 captures and 22,452 single records of 147 species. Mist-net data showed that understorey bird diversity was positively correlated with logging intensity up to c. 3 trees per ha, reflecting increased influx of open-land species and a persistence of forest obligates during the first 5 years after logging. The overall abundance of forest interior species tended to decrease 5–10 years after logging, but recovered fairly well thereafter. Canopy birds were generally more logging-resilient. Rare forest obligates with high conservation importance were found to be equally abundant in virgin and logged, large forests, whereas these birds were poorly represented in small heavily logged forests. The results are compared with findings from other regions, and conservation implications and constraints are discussed in a global perspective. Finally, recommendations on size-related sustainable extraction levels and regeneration time are presented for the Upper Guinea Forest.
Long-distance seed dispersal influences many critical ecological processes by improving chances of gene flow and maintaining genetic diversity among plant populations. Accordingly, large-scale movements by frugivores may have important conservation implications as they provide an opportunity for long-distance seed dispersal. We studied movement patterns, resource tracking, and potential long-distance seed dispersal by two species of Ceratogymna hornbills, the black-casqued hornbill C. atrata, and the white-thighed hornbill C. cylindricus, in lowland tropical forests of Cameroon. We determined fruiting phenology of 24 tree species important in hornbill diet at monthly intervals and compared these patterns to monthly hornbill census data. After capture and radio-tagging of 16 hornbills, we used radio telemetry by vehicle and fixed wing aircraft to determine the extent of long-distance movements. Hornbills exhibited up to 20-fold changes in numbers in response to fruit availability in our 25 km(2) study area. Also, hornbills made large-scale movements up to 290 km, which are larger than any movement previously reported for large avian frugivores. Together, these observations provide direct evidence that hornbills are not resident and that hornbills track available fruit resources. Our results suggest that Ceratogymna hornbills embark on long-distance movements, potentially dispersing seeds and contributing to rain forest regeneration and diversity.
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.
The reproductive biology of two species of African hornbill, the Black-casqued Hornbill, Ceratogymna atrata, and the Whitethighed Hornbill, Ceratogymna cylindricus, was investigated over a four-year period (1994–1997) on a 25km 2 site in lowland rainforest in south-central Cameroon. Nesting attempts varied considerably among years, with the percentage of successful nests highest in 1995, with 64% and 54% of Black-casqued and White-thighed Hornbill fledging offspring, respectively. There were no nesting attempts in 1994, despite the fact that hornbills were present in the study area. Large differences in fruit availability were also noted across years, suggesting that reproductive activity and success are related to fruit availability. Data collected from 38 nests, over four breeding seasons (1994–1997), showed a preference for nest cavities in larger trees within areas of the forest containing larger trees. Hornbills did not show preferences for particular tree species, with the possible exception of Petersianthus macrocarpus, in which nine of the active nest cavities were found. Comparisons showed few significant differences in cavity characteristics between the two species . While cavities may have been a limiting factor in nesting in 1995, the year with the highest fruit availability, cavities were not limiting during other years when fruit availability was lower. Hornbill diets, as determined from seed traps at cavities, showed significant year-to-year variation. Although courtship and exploratory behaviour of cavities by pairs took place in most years, females did not wall themselves into cavities unless fruit was plentiful. Hornbills appear to time reproduction to coincide with peak food supply and successfully reproduce only when food is plentiful, and may curtail or forego nesting in years when fruit availability is low.
Distance sampling, line transects and radio-tracking have been used previously to estimate population abundances and movements of hornbills. We used a large dataset of audio recordings made over 10 years to estimate seasonal variation in abundance of three species: Black-casqued Hornbill Ceratogymna atrata, Yellow-casqued Hornbill C. elata and Brown-cheeked Hornbill Bycanistes cylindricus, in Tai National Park, Cote d'Ivoire. The latter two species are Near Threatened. Recordings of hornbill wing-beats were used to control for potential seasonal variation in call production. Yellow- and Black-casqued Hornbill calls were 10 times as abundant from July to February as they were from March to June. Brown-cheeked Hornbills showed a similar trend, but less pronounced. From these data we concluded that large numbers of Yellow- and Black-casqued Hornbills had left the Tai National Park during this period. The significance of these findings is discussed in relation to the fragmentation and regeneration of the Upper Guinea forests and the relatively small size of the remaining forest habitat in the region.
Almost nothing is known of the effects of forest fragmentation on bird diversity within the heavily degraded and fragmented forest remnants in West Africa. We examined the effects of edge, fragment size and isolation on bird species richness in southwestern Nigeria where forest fragmentation is pronounced. In total, 122 km of line transects were used to survey birds and vegetation within 45 forest patches between January 2000 and March 2002: 197 species were recorded. Avian species number and total counts in forest patches were unrelated to fragment area (within the observed range of 14–445 ha), but were negatively influenced by degree of isolation and increasing distance from the edge. As the total area of forested land within 15 km of a patch fell from 4 to 0%, so 21% of species were lost. In total, six and zero species (of 154 recorded more than once) were consistently recorded in the larger and smaller forest fragments, respectively, and four and two bird species were consistently recorded in unisolated and isolated forest fragments, respectively, suggesting that the addition of ‘edge’ species did not compensate for loss of species sensitive to fragmentation. Diversity index was not affected by either fragment area or degree of isolation, but decreased with distance from the edge. When individual species counts were considered, 68% of species (n = 62) showed no significant effect of distance to edge. Of those 20 species which showed an effect, 12 were less common close to the edge. Most species (65%) did not respond significantly to increasing isolation but of those 22 species that did, 20 were less common in more isolated fragments. Ninety-seven per cent of species showed no significant response to area. As avian diversity and species composition, but not species number, were apparently insensitive to forest fragmentation, our findings suggest that fragmentation reduces the probability of occurrence of a wide range of West African bird species, rather than a subset of fragmentation-sensitive species. The greater apparent sensitivity of present-day West African forest bird communities to fragmentation rather than patch size might reflect previous extinctions of area-sensitive species. Minimizing further forest fragmentation might be the most effective means of conserving avian diversity in current West African landscapes where most remaining forest patches are small (i.e. < 500 ha).
Ghanaians have a long history in ivory, both for export and for carving. From the 1970s to the early 1990s, however, most of Ghana's elephant were killed either by local farmers in retribution for human-elephant conflict or by poachers for the ivory trade. Ghanaian ivory craftsmen used the tusks primarily to make jewellery and figurines over this time. These curios were mostly sold in Accra, the capital, but due to lack of market surveys, very little data are available. In July 2010 I surveyed the retail outlets selling ivory in Accra and counted only 10 items on display in an art gallery and 85 items brought to me in five of 186 souvenir shops and stalls I visited. The reason there were so few items was that the Ghana Police Service and Wildlife Division of the Forestry Commission had carried out a raid in November 2008 in the main curio market confiscating several hundred kilos of ivory items, fining and imprisoning the dealers. Since then the vendors in Accra have feared to sell ivory. Elephant poaching declined at the start of the 21st century thanks to improved law enforcement. In 2004 a new system was introduced that involves performance and adaptive management through the monitoring of patrol effort and observations by the field-staff in the Wildlife Division. The combined effect of performance and adaptive management was that the number of effective days spent in the field by an average Wildlife Guard doubled, which dramatically lowered the number of elephants killed illegally. In addition, governance improved, Ghanaians developed greater respect for the law and there was less corruption, which reduced elephant poaching and the sale of ivory objects. This paper concludes that Ghanaian examples of greater patrol staff performance through improved monitoring—and of successfully raiding outlets selling illegal ivory—are a sound approach to reducing elephant poaching. While improving anti-poaching exercises is more difficult in some African range States, the Ghanaian example of shop raids is easier to implement and has also worked in countries such as Cameroon and Ethiopia. Other countries in Africa, especially Cote d'Ivoire, Democratic Republic of Congo, Nigeria and Senegal, need to follow the example of Ghana in carrying out official raids on ivory in retail outlets.
The exceptionally rapid degradation and fragmentation of the Upper Guinea Forest, caused by slash-and-burn farming and selective logging, oblige bird conservationists to examine critically the conservation value of unprotected areas, which may provide buffer zones or connecting corridors to protected forests. This paper assesses the utilisation of various tree-crop plantations by mainly lower storey forest birds in south-west Ghana, through avifaunal comparisons of shaded cash crops (rustic cocoa; neglected coconut) and exotic tree plantations (Cedrela, Gmelina) with nearby closed forest. Plantations adjacent to, or within, large (.200 km 2), biodiverse forests are superior bird habitats compared to similar plantations within small (,50 km 2) and species-poor forests. A relatively high forest tree density in cash crop (15–20 ha À1) and exotic (15–35 ha À1) tree plantations, combined with a luxuriant woody undergrowth (not slashed for .5–10 years), may additionally explain the presence of many forest specialists, including regionally 'Vulnerable' and locally 'Endangered' species. Overall, 50% of species of conservation importance found in forests were represented in plantations. These findings highlight the importance of shaded plantations with long periods between understorey weeding, as appropriate land-use systems that enhance the area under effective conservation and improve the connectivity of protected forest fragments. Results are compared to similar studies in the Old and New World tropics, and implications for off-reserve land-use management are compared and discussed in regional and global contexts.
We estimated densities of parrot and hornbill species in primary and selectively logged forest and forest gardens at two lowland sites on New Britain, PNG. We related differences in abundance to food and nest-site availability in the different habitats and determined whether nest-site availability might limit local breeding populations. Blue-eyed Cockatoo Cacatua ophthalmica and Blyth's Hornbill Rhyticeros plicatus were usually rarer in forest gardens than in primary forest, but both fared well in logged forest. Eclectus Parrot Eclectus roratus was more common in all human-altered forests than in primary forest, and Eastern Black-capped Lory Lorius hypoinochrous was reasonably common throughout but extremely abundant in forest gardens at one site. Parrots and hornbills were recorded eating fruits of 15 tree species and flowers of nine species. Densities of these fruiting and flowering trees were highest in logged forest and forest gardens, respectively, indicating the importance of these anthropogenic habitats as feeding grounds for the assemblage. Active nest cavities were found in large individuals of 12 tree species. Densities of potential nest cavities were highest in primary forest and lowest in forest gardens. At both sites, estimates of potential nest-site density were significantly lower than estimates of the density of pairs of all species of parrots and hornbills: there may be 10–20 parrot/hornbill individuals per nest-hole. Continuing forest alteration, whilst further reducing nest-site availability, may allow large populations of parrots and hornbills to persist due to increased availability of food in some anthropogenic habitats. However, current abundance of such bird species may be a poor correlate of future extinction risk as long-lived taxa may remain common for some period even when annual recruitment has declined to critically low levels.
We investigated the effects of forest fragmentation on the disappearance of fruit-eating animals and the recruitment of animal-, wind-, and gravity-dispersed trees in 80-year-old forest patches in the East Us- ambara Mountains of Tanzania. We compared adult and juvenile trees in forest transects in a 3500-ha submontane forest with those in four forest fragments of 521,30,9, and 0.5 ha. Preliminary results show that recruitment of seedlings and juveniles of 31 animal-dispersed tree species was more than three times greater in continuous forest and large forest fragments (greater than or equal to 30 ha) than in small forest fragments (less than or equal to 59 ha), whereas recruitment of eight wind- and gravity-dispersed trees of the forest interior was unaffected. Recruitment of 10 endemic, animal-dispersed tree species was 40 times lower in small fragments than in continuous forest or large fragments. Counts of diurnal primates and birds in all five sites indicated that frugivorous species have declined with decreasing fragment size. These results are consistent with the idea that loss of dispersal agents depresses tree recruitment in the course of forest fragmentation.
This article explores spatial and temporal changes in diurnal primate abundance and behavior in response to hunting, logging, and conservation at the Dzanga Sangha Dense Forest Reserve (RDS), Central African Republic over time. We use a combination of line-transect surveys in 2002 and 2009 (N = 540 km) and ethnographic interviews (N = 210) to investigate changes in the status of cercopithecines and colobines at RDS, with additional comparisons to earlier work. This protected area was lightly logged in the 1970s and the park was gazetted in 1990, with multiple-use reserve sectors allocated. Since the park's inception, hunting and the trade of primates have increased, along with human migration, greater accessibility of arms, and reduction of preferred ungulate prey. Primates have declined in both the park and reserve sectors. Our data further suggest that at RDS hunting has had a greater impact on primate diversity and abundance than logging. We have identified changes in species-specific vulnerability to hunting over time, with Cercopithecus nictitans and Lophocebus albigena initially having appeared to be relatively resistant to hunting pressure in 2002. However, subsequently as gun hunting has increased at RDS, these species have become vulnerable. Although monkeys at RDS have been responding behaviorally to increased gun hunting, they are not able to keep pace with changing hunting practices. This study allows us to begin to understand synergistic impacts of hunting and logging, necessary if we are to recommend strategies to better secure the future of primates in multiuse protected areas.