Maintaining connectivity in tropical agricultural landscapes

Posted on 16 November 2016

Research directed by scientists at the University of York highlights how oil palm plantations may be barriers to the movement of rainforest species through agricultural landscapes, and highlights the importance of maintaining well connected areas of rainforest.

Fragmentation of natural habitat through deforestation and degradation can be a problem for rainforest species if they fail to cross habitat boundaries and cannot reach new locations.

This new research, recently published in the journal Biotropica, examines the movement of butterflies at rainforest-oil palm plantation boundaries in Sabah, Malaysian Borneo. As in many parts of Southeast Asia, Borneo has faced a severe loss of rainforest habitat in recent decades due to the expansion of the oil palm crop, threatening many rainforest species.

The study examines the ability of butterflies to cross rainforest boundaries in relation to their characteristics, including their wing size, number of food plants their caterpillars can feed on, geographic range size, as well as the presence or absence of their food plants within plantations. The new results suggest that boundary crossing from forest into oil palm plantations was relatively frequent for small-sized butterflies that could potentially breed within plantations, but forest butterflies crossed less frequently.

Lead author Sarah Scriven, who is just finishing her PhD at the University of York in the Department of Biology said: "This study gave me a fantastic opportunity to collect movement data on rainforest butterflies in Borneo. I used traps baited with rotten banana and hung them from trees at rainforest–plantation boundaries to catch butterflies that feed on fallen fruit. I marked the butterflies before letting them go, and then I knew whether the same individual was captured crossing into a different habitat."

Dr Suzan Benedick from the Faculty of Sustainable Agriculture, Universiti Malaysia Sabah, added: "Butterflies are an excellent group to work on if you are interested in studying habitat connectivity. Butterflies are not only mobile and relatively easy to mark, but their distributions also correlate well with other types of species, making the findings of wider relevance."

The research revealed that oil palm plantations may act as barriers to the movement of forest-dependent butterflies, which highlights the importance of conserving existing forest areas that form corridors linking forest reserves.

Co-author Dr Colin Beale, also from the Department of Biology at York, said: "Oil palm provides a valuable crop to many farmers in the tropics, but conversion of rainforest to oil palm plantations results in a dramatic change in habitat structure, making plantation habitats unsuitable for many rainforest species. Our study adds to the growing understanding that leaving a connected network of forest is the best way to allow forest species to move around the landscape."

Sarah's PhD supervisor, Professor Jane Hill, who is leader of the research project added: "Our results may also be important in the context of climate change because maintaining forest connectivity is crucial if species need to move across oil palm landscapes to reach cooler locations at higher elevation. We need to maintain connectivity to ensure tropical biodiversity is conserved in future."

Notes to editors:

  • Sarah Scriven collaborated with Jane Hill and Colin Beale at the University of York and Suzan Benedick from Universiti Malaysia Sabah (Faculty of Sustainable Agriculture). Her paper "Barriers to dispersal of rain forest butterflies in tropical agricultural landscapes" is published in Biotropica and is available online at: http://onlinelibrary.wiley.com/doi/10.1111/btp.12397/full
  • This research was funded by the UK Natural Environment Research Council (NERC) (grant number: NE/K500987/1).