Birds, traditional coffee plantations and spatial complexity: the diversity puzzle

E. Leyequien

Research output: ThesisPhD Thesis - Research external, graduation external


As the current accelerated and increasing loss of biological diversity have become apparent land managers and ecologists have sought to identify significant habitats to the preservation of biodiversity. A critical component of biodiversity protection is the understanding of the ecological forces shaping the species diversity patterns. The aim ofthisstudy is to gain insight in the local and regional factors ultimately controlling species persistence and coexistence. The conceptual background of this study is that ofadiversified multiple-use landscape matrix, that is used and managed and where "natural areas" can be embedded. Neotropical bird species are currently under threat as their breeding grounds suffer from degradation and loss because of intensification of land use. The fieldwork of this thesis was conducted in the northeastern mountain range ofPuebla,Mexico. This region represents an important area for the conservation of resident and migrant birds, as it is located in a strategic position at the Neartic and Neotropical biogeographic boundary. It also forms part of the migratory route for Nearctic-Neotropical birds. Moreover, despite the lossofprimary forests in the region, one ofthemain land uses in the study area is traditional shade coffee plantations which remain as an important forested habitat for birds. An important issue in conservation biology is the monitoring of community trends to provide reliable information of species diversity and their status, for fast and efficient identification of conservation priorities. In chapter 2, we analyse the use ofadouble-observer point count approach and mist netting for assessing bird species richness during migration. We assess the relative biases, costs and efficiency of both techniques to aim optimisation in the design of large-scale monitoring. We found that the double-observer point count technique was the most effective in the total species richness completeness and presented lower total effort in comparison to mist netting. The performance of point counts is higher than mist netting in the detection of new bird species in the research area, even after a large sampling effort. However, mist netting significantly detected a higher proportion of understory species in comparison to point counts, though we found opposite results for migrant species. Finally, the cost-efficiency analysis showed that the modified 209 double-observer point counts required less total effort thus decreasing total monetary costs compared to mist netting. One of the main problems in conservation in Latin America is the accelerated deforestation and conversion to monocultures and grazing lands that has direct effects on Neotropical avian communities (i.e. resident and migrants) leading to a major loss of habitat, and landscape fragmentation. In chapter 3, we analyse how fragmentation and habitat loss in the landscape influences the bird species richness patterns. We examine the relative individual and combined influence of these two factors on species richness in an avian metacommunity.Moreover, we compare the difference in explanatory power of individual and combined influence of both factors. The response of species richness to habitat fragmentationshows a unimodal response at landscape level, and a negative response to habitat loss. The combined influence of fragmentation and habitat loss did not offer a better approximation of species richness response. This suggests that there is no interaction between the effects of fragmentation and habitat loss. Assessment of the effects of habitat fragmentation and loss under the current situation of growing human perturbation in natural habitat is fundamental in conservation and landscape management. An important ecological force structuring ecological communities is interspecific competition. Body mass is an easily determined characteristic of animals that probably influences competition strength. In chapter 4, our objective is to examine the effect of body size (mass) on competitive interactions between competing pairs of bird species. Our results indicate that there is a significant negative relationship between bird body mass ratio and the competition strength i.e.; the larger the body mass ratio, the lower the competition strength thereby suggesting that high variation in body sizes amongstsympatricspecies may promote coexistence in communities. Moreover species that have a greater overlap in resource use tend to exhibit stronger competition than species that overlap less in their resource use. 210 In chapter 5, the influence of spatially explicit bio-physical variables at multiple scales on a bird community is analysed. We argue that biological communities are organised at multiple functional spatial scales and interactions between these scales determine both local and regional patterns of species richness. We use a multiple scale approach with plot, patch and landscape level variables using abundance and presence-absence data. Our results demonstrate that landscape variables explain most of the variation in bird species in both abundance and presence-absence analyses in all explanatory sets. Interestingly, results demonstrate that variation in community structure was described best at family-level than at genera- or species-level. Our results show that shade coffee plantations is one of the main land covers that positively influence the species richness, thus providing habitat for neo-tropical migrants and forest-dependent birds (e.g.; in this study some endemic and protected species). Thus, selecting the appropriate scale(s) of management in conservation strategies is essential in conservation of bird communities. The use of remotely sensed data has great potential to aid in explaining species diversity and community assemblage patterns at multiple scales. Besides, it can help to optimise sampling strategies or to allow testing of hypotheses regarding the spatial correspondence of species diversity patterns among different taxonomic groups. In chapter 6, we review how remote sensing has been used to assess terrestrial faunal diversity, with emphasis on proxies and methodologies, while exploring prospective challenges for the conservation and sustainable use ofbiodiversity.We grouped and discussed papers dealing with the faunal taxa mammals, birds, reptiles, amphibians, and invertebrates into five classes of surrogates of animal diversity: 1. habitat suitability, 2. photosynthetic productivity, 3. multi-temporal patterns, 4. structural properties of habitat, and 5. forage quality. It is concluded that the most promising approach for the assessment, monitoring, prediction, and conservation of faunal diversity appears to be the synergy of remote sensing products and auxiliary data with ecological biodiversity models, and a subsequent validation of the results using traditional observation techniques. 211 In chapter7,1present the conservation implications of shade coffee plantations as a refuge for Neotropical birds. The scenarios of loss and conversion of shade coffee plantations for biodiversity conservation and carbon sequestration emphasise on the ecological services that this agro-ecosystem provides. The reduction of shade coffee plantations in the studied region will have a deleterious effect on the species richness ofe.g.,resident birds with an estimated decline of0.006in species richness for every hectare the coffee area is reduced. These results could have significant consequences for conservation strategies as the amount of traditional shade coffee plantations has a positive linear relationship with the species richness of resident birds(p<0.001). Moreover, in our research area the calculated carbon stock of the total area covered by shade coffee plantations is257,7891C,which represents 1,288,943USD in carbon credits. Thus, with a reported current conversion rate of 0.4 % the results in carbon loss will be devastatinginjust one year. Although the conversion rate for the research area is unknown we approximate an almost negligible rate of conversion compared to the previously reported. The potential for the coffee producers as suppliers of carbon sequestration is calculated in approximately105USD/ha, which represents a considerable income compared to approximately an average of59USD/ha per coffee harvest. In addition, the value of shade coffee plantations as a component of the anthropogenicmatrix is stressed in this study. Traditional shade coffee plantations are cultivated mainly by small-scale community-based growers, the majority of them belong to some indigenous group. The indigenous form of utilisation ofthistropical agroecosystems denotes a multiple use strategy, which can be called adaptative management. This indigenous adaptative management has obvious socio-economic as well as ecological benefits. The ecological advantages ofshadecoffee agroecosystems are clear: a) high biodiversity maintenance, b) regulation of carbon cycle, c) soil protection, d) regulation of hydrological cycle and e) preservation of forest cover. The economic benefits derived from this tropical agroecosystems are sources ofgoods,services and energy for household subsistence and products for local, regional and international markets. To increase the effectiveness of conservation management, the value of suitable land for multiple uses, as a component of 212 theanthropogenicmatrix should be considered. For example, in the case of tropical bird species, such linkages could be maintained by using the man-modified landscapes, e.g.; traditional shade coffee plantations as these areas also harbour an ecological value as habitat.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University & Research
  • de Boer, W. Fred, Supervisor, External person
  • Skidmore, Andrew , Supervisor
Award date21 Apr 2006
Place of PublicationWageningen
Print ISBNs90-8504-416-2
Publication statusPublished - 2006
Externally publishedYes


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