Outside-the-Market Valuation of Ecosystem Services

Ecosystem services encompass the suite of resources and process perpetuated in natural systems that benefit humankind. These services can be thought of as assets obtained from nature. They include such things as the production of fresh water, the prevention of disease outbreak, the pollination of crops, the maintenance of biodiversity, and outdoor recreational opportunities.

Some of the ecosystem services attributable to wildlife include pollination, seed dispersal, nutrient dispersal, and pest control. With >1,000 species worldwide, bats have representative species performing each of these ecosystem services around the globe! Forty-seven species of bats are present in the United States, with 13 species considered year-round residents in Florida.

With the exception of a few uncommon bats in the Keys, all resident bats in Florida consume insects. Due to their small size and high metabolism, bats have exceptionally high energetic demands. This means that each bat consumes large quantities of insects each night. During the summer, when pregnant and nursing female bats have especially high energy requirements, each bat may consume as much as 2/3 of its body weight per night.

Some of the insects bats consume in large quantities are major pests of agricultural crops. For example, the Mexican free-tailed bat (Tadarida brasiliensis mexicana), consumes several species of moths that are agricultural pests in Texas. The fall armyworm (Spodoptera frugiperda), cabbage looper (Trichoplusia ni), tobacco budworm (Heliothis virescens), and corn earworm or cotton bollworm (Helicoverpa zea) are all consumed by this bat. The southeastern version of this species, the Brazilian free-tailed bat (Tadarida brasiliensis cynocephala), is common throughout Florida and typically lives in very large congregations. Studies are currently underway to determine whether these bats consume the same insect pests in the Southeast as they do in Texas.

Researchers have estimated the economic value of the pest control services Mexican free-tailed bats provide in Texas. DNA tests have confirmed that these bats regularly consume the corn earworm moth during the early part of the growing season in this state. Experts estimate that approximately 100 million bats occur in an eight-county region of south-central Texas, and these bats can consume 4 billion corn earworm moths per night. These bats have the potential to reduce the need for 1 or 2 insecticide applications each year, which could reduce costs by $19/acre on conventional cotton fields and $35/acre on transgenic cotton fields (costs reported in 2007). The total financial contribution of the bats was determined by estimating the value of the cotton crop that would have been lost if bats were not present, plus the cost of insecticides that would have been needed if bats had not consumed any insect pests, plus the social and environmental costs saved by the reduced use of insecticides. The value of the pest control services bats provide for cotton producers in south-central Texas was estimated to be $741,000 per year. Similar estimates have not yet been made in the Southeast.

Although cost estimates are not yet available for the ecosystem services provided by bats in Florida, it is clear that bats serve as valuable allies to humans by consuming enormous quantities of night-flying insects, many of which are pests to humans and to crops. Because Brazilian free-tailed bats frequently live in man-made structures, this species could be attracted to areas were additional pest control services are desired. Furthermore, because this species tends to live in large groups and tends to feed on numerous important agricultural crops in Texas, it is likely to have substantial impacts when incorporated into integrated pest management (IPM) strategies in Florida.

If you wish to learn more about bats, additional information can be found in EDIS publications on the following topics:

For more information contact Holly Ober.

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