Abstract
The enormous global burden of vector-borne diseases disproportionately affects poor people in tropical, developing countries. Changes in vector-borne disease impacts are often linked to human modification of ecosystems as well as climate change. For tropical ecosystems, the health impacts of future environmental and developmental policy depend on how vector-borne disease risks trade off against other ecosystem services across heterogeneous landscapes. By linking future socio-economic and climate change pathways to dynamic land use models, this study is amongst the first to analyse and project impacts of both land use and climate change on continental-scale patterns in vector-borne diseases. Models were developed for cutaneous and visceral leishmaniasis in the Americas—ecologically complex sand fly borne infections linked to tropical forests and diverse wild and domestic mammal hosts. Both diseases were hypothesised to increase with available interface habitat between forest and agricultural or domestic habitats and with mammal biodiversity. However, landscape edge metrics were not important as predictors of leishmaniasis. Models including mammal richness were similar in accuracy and predicted disease extent to models containing only climate and land use predictors. Overall, climatic factors explained 80% and land use factors only 20% of the variance in past disease patterns. Both diseases, but especially cutaneous leishmaniasis, were associated with low seasonality in temperature and precipitation. Since such seasonality increases under future climate change, particularly under strong climate forcing, both diseases were predicted to contract in geographical extent to 2050, with cutaneous leishmaniasis contracting by between 35% and 50%. Whilst visceral leishmaniasis contracted slightly more under strong than weak management for carbon, biodiversity and ecosystem services, future cutaneous leishmaniasis extent was relatively insensitive to future alternative socio-economic pathways. Models parameterised at narrower geographical scales may be more sensitive to land use pattern and project more substantial changes in disease extent under future alternative socio-economic pathways.
Highlights
Vector-borne diseases have globally significant impacts on public health and socio-economic development
Tropical ecosystems are under huge pressure from competing land uses and deforestation [8]
We considered a matrix of six alternative future scenarios organised around two important dimensions: the extent of climate change and possible future socio-economic conditions (Fig 2)
Summary
Vector-borne diseases have globally significant impacts on public health and socio-economic development. Impacts of ecosystem changes on vector-borne incidence depend on a complex interplay between ecological factors such as the ratio of competent to non-competent hosts and vectors (determined by species-specific responses to biodiversity or ecosystem change) [6] and social factors that determine the contact rates between humans and infected vectors [7]. This interplay is highly context dependent—in the terminology of the ecosystem service concept, ecosystems may provide the “disservice” of maintaining transmission cycles which may lead to infection of humans and/or the “service” of regulating those cycles and controlling spillover into human populations [3]. For tropical ecosystems understanding trade-offs between vectorborne disease “disservices” or “services” and other ecosystem services across heterogeneous landscapes [11] is critical for (i) prediction of health impacts of environmental and development policies that may alter ecosystems (ii) development of decision-support tools to target such measures [4, 12]
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