The missing link : bridging the gap between science and conservation

C.A. van der Hoeven

Research output: Thesisinternal PhD, WU


Conservation biology is faced with an implementation crisis. This crisis is the result of a “knowledge-doing” or “assessment-planning” gap. One reason for this is that there is a discrepancy between systematic classical scientific assessments or surveys, and actual implementation in the field. This thesis explores the state of conservation biology by discussing the practicality of several research activities that are needed in most biodiversity conservation projects. Classical conservation science is compared and combined with newly developed methodologies. The objective was to produce a more comprehensive information package for conservation planning and implementation. Research activities were analysed on complementarity, cost and time constraints, and on the possibilities of integrating local knowledge. This study was conducted in GEF-Campo-Ma’an project in the tropical rainforest area of south Cameroon. In chapter 2 a new method of wildlife density estimation is explained, which is less time and money consuming, but yields comparable results with classical methods. Methods currently used for assessing wildlife density in rainforests are time and money consuming. The precision of the most commonly used methods is disputed, but accepted because more exact methods are not available. The method was tested in the field and compared with transect surveys in the area and with relevant literature. The PLEO (Pooled Local Expert Opinion) method is based on the knowledge of local experts. A number of hunters was asked to estimate wildlife abundance in a specified area, after which the density per km2 was calculated for 33 wildlife species. These estimates were pooled and extrapolated for the whole study area. Elephant (Loxodonta africana) density outside the National Park was estimated to be 0.06 animals per km2, and 0.3 inside. Buffalo (Syncerus caffer) density for the study area was estimated at 0.2 animals per km2 and gorilla (Gorilla gorilla) density at 1.05 per km2. Transect surveys carried out at the same time for considerably more money, taking far more time, produced too few data to calculate densities. The evaluation of the PLEO-method was favourable and the method offers a substitute for conventional methods of estimating wildlife density in rain forests. The methodology is simple and it can be incorporated in many tropical biodiversity and conservation projects. It can also be used for long-term monitoring of wildlife status in a given area. In contrast with classical methods, the PLEO-method is low in cost and assures local ownership of the results. In chapter 3 a new method is presented that ranks medium to large-sized mammals in a rainforest according to their vulnerability to extinction or to major population declines. It is a fast, efficient and cost-effective method to set priorities in conservation management. Information from the literature and local knowledge from hunters and forestry people were combined to assess the status of 33 wildlife species. The result is a vulnerability list, where species are ranked according to their vulnerability to major declines and extinction. To produce this list we developed a system where the risk-proneness of each species was determined on the basis of thirteen factors. These factors were assumed to be of importance to the survival of a population, and were scored with information from interviews with local hunters, and from the literature. The method was tested in the Campo-Ma’an area in south Cameroon. In this study the most vulnerable species was the mandrill, followed by the elephant, chimpanzee, and buffalo. Five of the ten most vulnerable species are on the IUCN red list of threatened species, which justifies the use of the new method to set local conservation priorities. We argue that for on-the-ground management this method provides a useful tool to allocate time and money to the species that need them most. Because detecting trends in wildlife populations remains difficult, other ways of monitoring are needed. Gathering socio-economical and biological data on bushmeat markets could be a relative easy way of monitoring the bushmeat trade. Although collecting data is fairly straightforward, analyses of these data are hardly ever conclusive on the sustainability of the off-take. Theoretical models that include as much variables as possible do perform quite well in simulations, but long-term, multi-variable datasets provide no clear-cut answer yet. Chapter 4 presents a survey that selected only a few factors that are thought to indicate the state of the trade, and analyzed the relations between these dependent factors and several fixed (independent) factors that are hypothesized to influence this state. The factors assumed to be indicative of the bushmeat trade are: the price, the state (the percentage smoked meat), and the diversity of the bushmeat for sale (in terms of number of species for sale). These are thought to be related to several factors that influence hunting pressure, which are: human population size (as a proxy for the demand for bushmeat); distance between local market and city markets; and distance to the National Park; and the wildlife density in the area surrounding the market. Two clear relations were found after analysis. These are a negative correlation between the price of the bushmeat and the distance to the city; and a negative correlation between the percentage of smoked meat at the market and the wildlife density in the area surrounding the surveyed market. The negative effects of roads on wildlife in tropical rainforests in Africa are poorly understood. Road construction has high priority in Africa, with as effect that negative impacts of roads on wildlife often are neglected. Chapter 5 provides information on the effects of roads on crossing behaviour of rainforest wildlife. Crossing probability of forest wildlife was analyzed for association with ten different factors that were linked to road presence or road construction. Factors were divided into three classes: vegetation cover, topography and human influence. Spoor plots were laid along a 32 km unpaved logging road that divides Campo-Ma’an National Park. Tracks of several species were found frequently (e.g., genets and porcupines); while others were found only sporadically (e.g., forest duikers and apes). Differences in crossing behaviour between plots along the road and in the forest interior supported the hypothesis that the presence of a road acts as a barrier for most species. The actual physical obstacles found along the road (e.g., logs, banks, etc.) proved to be highly negatively correlated with crossing probabilities. High vegetation cover was positively correlated to crossing probability. This study proves that roads have a large impact on wildlife, and indicates which factors could be altered during road construction and maintenance in order to mitigate these impacts, such as to maintain a high vegetation cover at shrub level up to the road, and to prevent the roadside from being blocked during construction. During the study described in chapter 5, the colonisation of roadsides by an invasive plant species was discovered. We surveyed the level of invasion of the roadsides by the invasive shrub Chromolaena odorata and found that native plant species of the African ginger family (Zingiberaceae) were outcompeted (chapter 6). Zingiberaceae form a key resource for the lowland gorilla. Abundance of these gingers has been largely reduced through displacement by Chromolaena odorata in two years time in Campo-Ma’an National Park in Cameroon. The invasion of this shrub in the whole rainforest region of central Africa and subsequent disappearance of the original vegetation threatens the gorilla in its already precarious existence.   Merging local knowledge in classical scientific activities is possible in a scientific sound way. The advantages in terms of cost and time benefits, plus the potential of increased commitment of the local population to conservation argues for this approach to be adopted on a larger scale. When the first three case studies (chapters 2, 3, and 4) are combined, species and site specific information can be generated that provides on-the-ground management with the means to set conservation priorities. By combining the vulnerability assessment, the base-line density assessment and the level of exploitation in the market survey, a comprehensive analysis of the state of the wildlife emerges. The risk of not noticing threatened species is in this way reduced. Although more practical and solution-based research within conservation biology is imperative for more effective conservation, fundamental and long-term classical research remains necessary. But only, given the time and money constraints, if they are based on specific questions posed by conservation planners and practitioners. The case studies (chapters 5 and 6) are examples where there is a clear link between classical scientific research and the requirements from conservation planners. Reconsideration of the role of conservation science is necessary, and testing of new methods proves that it is worthwhile to leave the beaten track. This does require a change of attitude of the conservation biologists. Only by trying new approaches and by testing new methods can one advance conservation. This thesis provides a start by presenting case studies which should stimulate further progress in conservation biology.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
  • Prins, Herbert, Promotor
  • de Boer, Fred, Co-promotor
Award date29 Oct 2007
Place of Publication[S.l.]
Print ISBNs9789085047568
Publication statusPublished - 2007


  • nature conservation
  • wildlife
  • research
  • data collection
  • techniques
  • rain forests
  • species

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