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A raft of recent studies has highlighted a major decline in large mammal populations in many of Africa's protected areas. A recent continent-wide assessment represented a major step forward also in terms of quantifying the decline on a regional basis, but fell short in its sampling and analysis. In this paper, a way out of the “black box” of large mammal declines in Africa's protected areas is formulated, with the aim of assisting in the preparation of further assessments in the future. First, large mammal assessments are categorized, highlighting the importance of using and sometimes juxtaposing peer-reviewed sources. The importance of the length of time series of large mammal counts is stressed, allowing one to distinguish between natural variation (especially rainfall) and human-induced changes. Setting reference dates, such as 1970, often gives biased results, showing the need to interpret large mammal population assessments in a historic context as well. This holds true particularly for West-Central Africa, which has experienced a considerable decline in rainfall since 1970. Building on a framework that connects herbivore physiology and behavior with environmental gradients, examples are given to explain some striking observed changes. The declines in Africa's protected areas are not limited to large mammals, but have also been observed for large birds of prey. Assessments of large mammal populations should be accompanied by the identification of proximate drivers of change, for which a framework is suggested in this paper. To conclude, some suggestions for countering the declines in large mammal populations are presented.
First-time comprehensive data on the community structure, species composition and regional endemism of dung beetle assemblage in a tropical montane cloud forest (TMCF) from South Asia is provided. High level of endemism, predominance of two montane endemic species of which one is a flightless local endemic, greater proportional abundance of roller guild, and the total absence of dweller guild, make the cloud forest dung beetle community different from the communities in the low-altitude montane forests. Distribution of major proportion of montane species in the low altitude supports the hypothesis for the origin of montane fauna through vertical colonization of the high altitudes by low-altitude species. Abundance of rollers is attributed to the availability of dung pellets of local endemic mountain goat, Nilgiri Tahr (Nilgiritragus hylocrius) and Sambar deer (Cervus unicolor) throughout the year and absence of dweller guild to the seasonal availability of fresh dung pads of Asian elephant (Elephas maximus) and gaur (Bos gaurus). Dominance by the flightless local endemic dung beetle Ochicanthon devagiriensis, belonging to the old-world tribe Canthonini with Gondwanaland distribution, indicates the stability, refugial isolation, and archaic nature of the dung beetle assemblage in the studied montane region. Since flightless species show a high level of fidelity to their preferred habitat and are efficient indicators of historical changes in their habitats, dominance and local endemism of flightless species Oc. devagiriensis makes it an ideal indicator species and effective forecaster of habitat modifications of the unique cloud forest study region in the Western Ghats.
Leaves of the palm Lepidocaryum tenue are one of the most prized thatching materials in northwestern Amazonia. We studied the population dynamics of this stoloniferous palm in Colombian Amazonia, using ramet-based Lefkovitch matrices, and assessed the impact of leaf harvest on population structure and dynamics, through experimental defoliation. Leaf production rate of unharvested palms ranged between 0.93 leaves per year in seedlings and 1.71 in adults. Vegetative shoots produced through stolons are more important than seedlings for maintaining the population; stolons act also as a reserve to overcome damage in the population. The potential population growth rate was 8.3 % per year (lgr; = 1.083). Juveniles had the highest contribution to population growth, and permanence was the most important life parameter. Thus, harvest of leaves for thatching can jeopardize the population if juveniles are also harvested. An initial harvest intensity of more than 50% of the leaves in a crown, or leaving the palm with fewer than four leaves, would have a negative impact on leaf production. Although matrix modeling suggests that all adult ramets can be harvested, this must be taken with caution, as clonal integration may play an important role in population dynamics. Long-term harvest of Lepidocaryum leaves is possible, if plots are harvested in turns of four years, thus allowing palms to recover from the previous harvest. A better control on the quality of the braided tiles sold in the market would also ensure their longer duration, thus reducing the pressure on the resource.
Deforestation and conversion of native habitats to exotic pasture and crops, plus inefficient agricultural and cattle management practices, are placing great pressures on natural resources in the Pantanal and Cerrado. To prevent further deforestation and protect biodiversity, areas already developed for farming and ranching need to be managed more efficiently and profitably, so that economic incentives for additional deforestation are minimized. To that end, the Wildlife Conservation Society (WCS) has been working with rural community partners to promote best-management practices that optimize profitability and efficient use of developed lands, while minimizing pressures on natural resources. To improve pasture conditions and reduce cattle impacts, we evaluated the use of rotational grazing as a management tool by monitoring native pasture and cattle within continuous and rotational grazing areas on a southern Pantanal ranch. Monthly comparisons of the grazing systems showed that forage dry mass in the rotational area was greater compared to that of continuously grazed areas. After 17 months, mean cattle weights were 15% heavier and pregnancy rates 22% higher for the herd using the rotational system. Based on forage allowance estimates, the potential stocking rates of the rotational system were 2 to 6 times higher than rates typical of continuously grazed areas in the Pantanal. Results support the use of rotational grazing in native pasture areas of the Pantanal.
Effective conservation needs a solid baseline of animal distribution, density, and abundance data to base management strategies on and evaluate the effectiveness of conservation efforts on the species of interest. For many species it is not feasible to directly count individuals, and scientists are forced to use indirect methods that can provide estimates of density and abundance. For orangutans nest counts are the most often used indirect sign of presence. Models used for density and abundance estimates are based on a set of assumptions about the observations. Here we analyze the effect of several factors (distance to transect, height, decay stage, and observer experience) on the probability that an orangutan (Pongo abelii) nest is found along a line transect. The results indicate that all factors significantly influence nest detection. Orangutan density estimates varied between the teams with the lowest estimate being approximately 83% of the highest estimate and orangutan density showed a positive correlation to experience level. We use these results to propose a new approach to determine orangutan density that should reduce variation between density estimates from nest surveys and therefore should lead to more reliable between-survey comparisons for orangutans and potentially other great-ape species.
The Andes range and the Amazon basin represent the most diverse biological community on earth and the largest tropical forest on earth, respectively, but they are historically understudied by biologists. In this paper we provide the first quantitative description of the volume and geographical distribution of ecological research in these regions. We compiled a dataset of all articles based on the Andes and Amazon regions published in two prominent international tropical ecology journals between 1995 and 2008. During this period, the number of scientific articles based on research in the Amazon was half that based on research in Central America, while the Andes scored among the least-studied of all tropical regions. Brazil was the leading base for Amazonian studies and Ecuador the primary location for Andean studies, but Ecuador led both categories and Brazil came last when research effort was standardized by area. Most Amazonian research took place in three regions—Manaus, southeastern Peru, and eastern Ecuador—with ∼31 percent of all papers coming from four field stations in those regions. Andean research focused overwhelmingly on the northern Andes. Research in the Andes range and the Amazon basin remains scattered, patchy, and far below its potential. We propose steps that funding agencies can take to increase research output and reduce geographical bias in the study of South America's richest ecosystems.
Conservation of biodiversity and of endangered tree species in tropical forests represents a challenge in the era of deforestation and overlogging. Assessments of biodiversity and of conservation species are essential to estimating the conservation value of ecosystems in order to develop appropriate management measures. This paper discusses the floristic composition, the diversity, and the regeneration of the conservation species in a logged forest in southern Vietnam. Twenty five one hectare plots have been set up using circular sub-plots of 8 metres diameter and at a distance of 10m from the centre point of other sub-plots. The sampling is approximately 50% in each plot. Ten years after the last logging, the species richness appears low, when compared with the close protected area, but the diversity is quite high and conservation species still occur. Twelve conservation species have been studied from the point of view of their distribution and regeneration. Some are close to extinction but some others show promise in terms of regeneration. Six floristic groups have been identified and, among them, two are of interest from a conservation point of view. This logged forest still has a high conservation value, and the process that aims at developing protection measures is clearly relevant.
The pulmonate land snail, Limicolaria flammea (Müller, 1774), is native to West Africa and its invasive potential is hitherto unknown. We report this species in Asia, specifically on the tropical island of Singapore. The presence of this alien species is of grave concern because its congener (L. aurora) has invaded the French West Indies and the confamilial giant African land snail (Achatina fulica) has colonized the globe to an extent where it is regarded as one of the world's worst 100 invasive alien species. In order to curb the spread of L. flammea into the native forests in Singapore, local authorities should start employing mechanical eradication methods (e.g., handpicking). We hypothesize that L. flammea arrived together with an exotic plant species, whose identity and import origin must be determined urgently to prevent the spread of this species into the rest of tropical Asia.
With very scanty information on invasive alien species (IAS) in Nigeria, this study was conducted to identify the invasive species in the field gene bank of the National Centre for Genetic Resources and Biotechnology (NACGRAB), Ibadan, Nigeria, on the latitude 7° 22′ north of the equator and longitude 3° 50′ east of the Greenwich Meridian, and also to assess the level of the species' disturbance to the conserved native plants in the protected area. This study involved sampling of the field gene bank and an on-site assessment and identification of the species and their effects on the indigenous plants established in the field for conservation. Twenty-five invasive plant species were identified, across 16 plant families, of which 14 were herbs, followed by vines, shrubs, and trees, all of which are presently estimated to occupy about 18% of the gene bank. The effects of IAS on the indigenous plants conserved in the field gene bank range from competition for space and nutrients and alteration of the tree canopies (thereby affecting the microclimatic conditions in the lower strata) to obstruction of the plants' reception of sunlight (which could thereby reduce the potential yield of the fruit trees in the gene bank. The paper also discusses the effects of IAS on biodiversity conservation in Nigeria. Human disturbance was observed as the major factor responsible for the spread of these IAS in the gene bank. The paper concludes by advocating stricter screening measures before introducing new plants into the country, capacity building on the early detection and management of IAS in protected areas for the technical staff, biological control, and exchange of technical information among concerned countries.
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