Higher forest cover and less contrasting matrices improve carrion removal service by scavenger insects in tropical landscapes

This post is also available in Spanish (here) and Portuguese (here)

In their latest research, Alvarado-Montero et al. assess the impact of landscape structure and matrix contrast on carrion removal by scavenger insects, an often overlooked but crucial ecosystem service which is important for nutrient cycling and disease control.

Carrion is something that many people choose to avoid. However, animals involved in carrion decomposition play a key-role in ecosystem functionality. Carrion removal by scavengers (ie. vultures, some mammals, or insects) prevents carcass accumulation, facilitates nutrient distribution and cycling, enriches soil fauna, and even prevents the outbreaks of dangerous diseases, like rabies and Ebola. Benefits such as these are referred to as ecosystem services.

Carrion attracts a great diversity of insects from different orders (ants, flies, beetles) that colonize or disappear from the carcass as it decomposes. The insects that colonize the carrion also depend on the environmental conditions the carrion is under. In this study, we decided to evaluate carrion removal by insect scavengers with exclusion experiments, and using a landscape perspective.

AM fig 1
Fly larvae opening and consuming soft tissue in our exclusion experiment — South Minas Gerais, Brazil. Photo: Sebastián Alvarado-Montero.

Understanding the links between biological communities and the provision of ecosystem services through mechanisms driven by landscape structure can facilitate management strategies that promote more sustainable landscapes. We therefore we tested the impact of landscape structure and agricultural matrix contrast on carrion removal by scavenger insects. We also compared the species richness and composition of scavenger insects in native forest patches and contrasting adjacent agricultural matrices types (coffee plantations and cattle pastures) spanning a gradient of forest cover and fragmentation in the Brazilian Atlantic Forest.

Our results showed that fragmentation in the region led to increased species richness of scavenger insects. However, these species-rich communities were mostly dominated by disturbance associated species, and such increase on scavenger species richness was not necessarily related to increased carrion removal. On the contrary: carrion that attracted less species (but very efficient species, like dung beetles), was removed more efficiently. This highlights the importance of having the ‘right’ set of species in order to obtain increased ecosystem services provision.

AM fig 2
A dung beetle from the Deltochilum genus removing a large ball of carrion from one of our baits inside the exclusion cage. South of Minas Gerais region, Brazil. Photo: Sebastián Alvarado-Montero.

The most efficient scavenger species were forest-associated species (i.e. flies of the Mesembrinellidae family, dung beetles and Silphidae beetles), which tended to have larger bodies than the species found in the agricultural environments. This allowed them to consume and manipulate larger amounts of carrion than smaller species, ending up in increased carrion removal service. We also found that increasing forest cover at the farm scale (200m around the sampling plots) increased the richness of highly-efficient scavenger insects, and thus carrion removal services.

We also found that carrion removal was efficient not only in-native patches, but also in coffee plantations, while such provision was strongly diminished in cattle pastures. The increased carrion removal in coffee plantations is a result of the presence of forest-associated species in these crops, as they were completely absent in the high-contrasting pastures. Such process is often intensified in more forested landscapes and when the agricultural matrix is more permeable (e.g. coffee plantations).

The conservation of forested areas or restoration of less productive environments interlinked with agricultural areas could ensure or increase the spillover of carrion removal services into anthropogenic matrices with benefits for the farmer. Additionally management strategies aimed at reducing the contrast between forest areas and agricultural matrices can increase landscape connectivity for species that are more efficient at providing carrion removal service.

We are grateful to all farmers from the region who allowed us to develop this research within their lands. We are also thankful to Welton Luis Antonio for his assistance during the whole execution of this fieldwork. This research was supported by São Paulo Research Foundation (FAPESP), by the National Council for Scientific and Technological Development (CNPQ) and by the Brazilian Ministry of Education (CAPES).

The full paper Higher forest cover and less contrasting matrices improve carrion removal service by scavenger insects in tropical landscapes in Journal of Applied Ecology.

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