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A wide range of species, from birds to butterflies, engage in migration – seasonal relocation of populations. As part of our research focusing on transboundary ecosystem services, we are researching the cross-border ecosystem services provided by migratory bats, which rely on habitat in specific locations yet provide valuable ecosystem services, mainly pollination and pest control, in other locations. This situation may present significant policy challenges, as locations that most support a given species may be in effect subsidizing the provision of services in other locations, often in different political jurisdictions.
Large numbers of bats migrate between summer and winter sites in southwestern United States and northern Mexico, establishing large colonies.
These bats serve as mobile links connecting ecosystem processes in one location with the provision of ecosystem services in other areas.
For example, two species of endangered, long-nosed bats pollinate blue agave, the main ingredient of tequila. Corporate tequila producers in Mexico currently propagate agave plants vegetatively and only cultivate 1-2 genetic varieties. Pathogens have devastated the genetically homogeneous crops twice, resulting in substantial economic losses. If bats were allowed to pollinate agave, cross-pollination would increase genetic diversity and pathogen resistance. The regulating services provided by long-nosed bats are clearly important for sustainable agave crops.
Another migratory species, the Mexican free-tailed bat, provides critical pest control services for cotton crops in the southwestern United States and northern Mexico. Female bats migrate annually and form large roosting colonies, up to 20 million individuals, from central Mexico to the US-Mexico borderlands. The females feed on agricultural pests - corn earworm and cotton bollworm - providing an estimated $700,000 worth of pest control annually in one region of Texas.
Several factors threaten the bats and the services they provide. Millions of bats have been burned, dynamited, or barred from their roosts by ranchers who mistake them for vampire bats. Bat caves have also been destroyed or disrupted by urban development, highway construction, vandals, and undocumented migrants crossing the US-Mexico border.
To develop a more quantitative understanding of the bats’ migration and habitat needs, we are developing an multi-model that integrates models of Mexican free-tailed bat migration with models of bat ecosystem service provision. This will allow us to quantify how much different regions support the bat populations and to assess bat vulnerability to human-related disturbances including habitat loss, pesticides, and climate change.
Land-use decisions in one country (United States or Mexico) may affect landscape/habitat (forage, water, and roosts) in that country, in turn impacting bat populations. After the bats migrate, the supply of ecosystem services in the other country also may be affected.