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The value of small size: loss of forest patches and ecological thresholds in southern Madagascar
Stockholm University, Faculty of Science, Department of Systems Ecology.ORCID iD: 0000-0002-8218-1153
Stockholm University, Faculty of Science, Department of Systems Ecology.
Stockholm University, Stockholm Resilience Centre.
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2006 (English)In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 16, no 2, 440-451 p.Article in journal (Refereed) Published
Abstract [en]

Many services generated by forest ecosystems provide essential support for human well-being. However, the vulnerability of these services to environmental change such as forest fragmentation are still poorly understood. We present spatial modeling of the generation of ecosystem services in a human-dominated landscape where forest habitat patches, protected by local taboos, are located in a matrix of cultivated land in southern Madagascar. Two ecosystem services dependent on the forest habitats were addressed: (1) crop pollination services by wild and semidomesticated bees (Apoidea), essential for local crop production of, for example, beans, and (2) seed dispersal services based on the presence of ring-tailed lemurs (Lemur catta). We studied the vulnerability of these ecosystem services to a plausible scenario of successive destruction of the smallest habitat patches. Our results indicate that, in spite of the fragmented nature of the landscape, the fraction of the landscape presently covered by both crop pollination and seed dispersal services is surprisingly high. It seems that the taboo system, though indirectly and unintentionally, contributes to upholding the generation of these services by protecting the forest patches. Both services are, however, predicted to be very vulnerable to the successive removal of small patches. For crop pollination, the rate of decrease in cover was significant even when only the smallest habitat patches were removed. The capacity for seed dispersal across the landscape displayed several thresholds with habitat patch removal. Our results suggest that, in order to maintain capacity for seed dispersal across the landscape and crop pollination cover in southern Androy, the geographical location of the remaining forest patches is more crucial than their size. We argue that in heavily fragmented production landscapes, small forest patches should increasingly be viewed as essential for maintaining ecosystem services, such as agricultural production, and also should be considered in the ongoing process of tripling the area of protected habitats in Madagascar.

Place, publisher, year, edition, pages
the Ecological Society of America , 2006. Vol. 16, no 2, 440-451 p.
Keyword [en]
forest fragmentation, graph, habitat loss, pollination, seed dispersal, small habitats, southern madagascar
National Category
Ecology Biological Sciences
URN: urn:nbn:se:su:diva-25689DOI: 10.1890/1051-0761OAI: diva2:200272
Part of urn:nbn:se:su:diva-844Available from: 2006-02-10 Created: 2006-02-10 Last updated: 2014-11-07Bibliographically approved
In thesis
1. A network perspective on ecosystems, societies and natural resource management
Open this publication in new window or tab >>A network perspective on ecosystems, societies and natural resource management
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis employs a network perspective in studying ecosystems and natural resource management. It explores the structural characteristics of social and/or ecological networks and their implications on societies’ and ecosystems’ ability to adapt to change and to cope with disturbances while still maintaining essential functions and structures (i.e. resilience).

Paper I introduces terminology from the network sciences and puts these into the context of ecology and natural resource management. Paper II and III focus on habitat fragmentation and how it affects an agricultural landscape in southern Madagascar. Two ecosystem services were addressed: (1) crop pollination by bees, and (2) seed dispersal by ring-tailed lemurs. It is shown that the fraction of the studied landscape presently covered by both crop pollination and seed dispersal is surprisingly high, but that further removal of the smallest habitat patches in the study area could have a severe negative impact on the landscape’s capacity to support these ecosystem services.

In Papers IV and V, the network approach is used to study social networks and the impact they may have on the management of natural resources. In Paper IV it is found that social networks of low- to moderate link densities (among managers) significantly increase the probability for relatively high and stable utility returns whereas high link densities cause occasional large-scale ecological crises between periods of stable and excessively high utility returns. In Paper V, social networks of a rural fishing community in eastern Africa were analyzed. The results indicate that patterns of communication partly explain the distribution of ecological knowledge among villagers, and that gear type used by small-scale coastal fishermen strongly correlates with their patterns of communication. The results also show that groups most central in the network, and hence potentially most influential, are dominated by one type of fishermen.

Place, publisher, year, edition, pages
Stockholm: Institutionen för systemekologi, 2006. 198 p.
network, seed dispersal, pollination, natural resource management, lemur catta, social networks, landscape fragmentation, Madagascar, East Africa, fisheries, resilience, co-management
National Category
Natural Sciences
urn:nbn:se:su:diva-844 (URN)91-7155-207-3 (ISBN)
Public defence
2006-03-17, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 8 C, Stockholm, 09:00
Available from: 2006-02-10 Created: 2006-02-10Bibliographically approved

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Bodin, ÖrjanTengö, MariaNorman, AnnaElmqvist, Thomas
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