Article published by Civil Eats
Written by Ruscena Wiederholt
May 6, 2024
Nearly a quarter of U.S. mammal species are on the endangered species list. Researchers say farming with biodiversity in mind may help stave off further decline.
Tom Farquhar planted several large plots of beneficial flowers around his vegetable farm in Montgomery County, Maryland. Once a conventional corn and soybean farm, the idea was to control pests at the Certified Naturally Grown operation by increasing the number of beneficial predator insects and spiders. And the method worked: “We don’t have too many big insect problems,” he said.
But the crop-free plantings have had another effect, Farquhar explained. They have also increased the number of mammals on the farm. Strips of trees, bushes, grasses, or flowers around agricultural or pasture fields can house higher numbers of small mammals than cropland. Additionally, the diversity of Farquhar’s crops and the chemical-free nature of his farm also attracted and supported small mammals, he said.
“We see lots of rabbits, groundhogs, mice, and voles in our fields,” he wrote in an email to Civil Eats. “Also, raccoons, especially when sweet corn is ripening.”
Because small animals can damage crops, the farm fortunately also has predators such as foxes, hawks, and eagles helping keep them in check. “The coyote is now a resident in our area, and that was never true until recently,” said Farquhar. “Maybe in the last 10 years, [coyotes] began to come in, and they also will eat the small mammals. So, we got nature happening out there in a big way.”
While industrial farming feeds the multitudes, it is also a main driver of biodiversity loss across the country. More than 18 percent of North American mammals are decreasing in population, and nearly a quarter of the more than 400 mammal species in the U.S. are listed on the endangered species list.
In addition to every species’ inherent value, mammals are vital in the natural order. They play critical roles in their ecosystems, sustaining and keeping in check species higher and lower on the food chain. They disperse seeds, pollinate, and transfer nutrients across landscapes, supporting healthy plant populations, and they alter their environments in ways that enhance biodiversity. They even mitigate climate change.
“Maybe in the last 10 years, [coyotes] began to come in, and they also will eat the small mammals. So, we got nature happening out there in a big way.”
The burgeoning human population, however, means agricultural impacts are only set to increase. Agriculture already takes up over half of U.S. land, with cropland expanding by 1 million acres per year, fueling habitat loss for wildlife and mammals.
Yet these agricultural areas present a golden opportunity: What if farms could help other species, especially the charismatic, furred variety? While increasing the number of mammals on farms can create some challenges, losing the bulk of small and mid-sized mammals presents challenges that are even larger. And farming sustainably—with organic methods and techniques like agroforestry that encourage on-farm biodiversity—offers a ray of hope to slow the decline of our closest relatives.
The Impacts of Agriculture on Mammals
Though the changing climate, the spread of invasive species, and pollution all negatively affect wildlife, agriculture has had a massive impact on the world’s mammals.
First of all, farmland reduces mammals’ natural habitats and diminishes their ability to find shelter as well as food and prey, explained Koen Kuipers, a researcher at Radboud University in the Netherlands. For instance, agriculture can destroy forest habitats that certain bat species, like the endangered Indiana bat or northern long-eared bat, use for roosting and foraging.
Runoff from U.S. farms is also a main source of pollution for rivers, lakes, and wetlands. Excess nutrients from fields can wash into nearby waterways, one of the greatest threats for freshwater mammals including dolphins, otter, and terrestrial mammals that gather their food from waterways.
And that’s not the only bad news. Pesticides can harm or kill mammals and can also reduce prey and attract invasive species that compete with native mammals for resources, explained Gaurav Singh-Varma, a researcher at the University of British Columbia. For instance, mountain lions, deer, coyotes, foxes, and bobcats can die by ingesting bait meant for pests or by eating pesticide-contaminated prey.
“All the pesticides and fungicides or whatever type of management that big farmlands like to use can have a direct and indirect effect on the mammals in the area,” Singh-Varma said. “It affects the type of habitats that the animals can use.”
In addition, as the largest consumer of freshwater globally, agriculture pulls directly from freshwater habitats which, in turn, harms species such as beavers, rabbits, mink, otters, and water shrews.
How Mammals Help on Farms
Mammals are vital to the functioning of natural landscapes, including those devoted to agriculture.
For example, bats are voracious predators of insects that damage crops. By one estimate, these flying mammals save U.S. farmers $3.7 billion annually. Bats also pollinate plants such as bananas and guavas grown in Hawaii and Florida, agave in California, and coconuts in Puerto Rico.
Other mammals such as skunks, badgers, foxes, and coyotes also do their part to suppress insects, rodents, and other pests, as do wolves and deer.
Meanwhile, “beavers are natural hydrologists and so the dams they build allow water to pond in one place and you get more infiltration,” explained Daniel Rath, an agricultural scientist at the Natural Resources Defense Council (NRDC). “And the water that’s stored in the soil is then able to be used by growing plants. It helps with resilience to extreme weather conditions such as drought and floods.”
Even negatively viewed mammals can be beneficial. Deer, for example, help cycle nutrients and fertilize soil. In addition, burrowing mammals like mice and moles increase organic matter and water infiltration in soil, explained Rath.
In addition, despite concerns that the sustainable practices that support mammals may reduce crop yields, some indications point to the opposite conclusion.
“By diversifying the system, you provide a lot more habitat for these natural pollinators to pollinate crops,” said Singh-Varma. “And there’s research to suggest that in these diversified systems, you can have smaller plot levels, or farmland, but still have an equivalent amount of output that you would get with conventional pesticide-heavy agricultural systems.”
He explained this boost may come from increased nutrient cycling and an abundance of species both above and below ground including native pollinators, birds, mammals, fungi, microbiota, and earthworms.
Supporting Mammals With Biodiversity
Though agriculture represents a top threat to mammals, when carried out with an eye toward biodiversity, it can also be a force for good.
“Diversification is an important step in acknowledging that agricultural systems are part of wider, complex natural ecosystems that are deeply interconnected and provide numerous benefits to society,” said Rath. “A diverse landscape that has a variety of plants, a variety of inputs, and a variety of land-use types can really help with that [wildlife] diversity.”
For instance, adding natural elements like hedgerows, or uncultivated strips about 15 feet in width, alongside agricultural fields can greatly benefit mammals, because they supply food and shelter to a variety of wildlife, including hedgehogs, bats, voles, and mice.
Agroforestry, or adding trees and shrubs to crops or pastures, is also advantageous—supporting a diversity of mammals including deer, black bears, squirrels, and bats, along with a variety of birds and invertebrates. The patches of shrubs in agroforestry provide protection and food for mammals, supporting these higher levels of diversity.
A recent study led by Kuipers looked at the benefits of diversifying agricultural landscapes in the U.S. and around the world for several mammals including bats, rodents, opossums, and hedgehogs. “We found that when these natural elements were included in croplands, and also for forest plantations, that species abundance and species richness can be similar . . . to natural reference conditions,” said Kuipers. Conversely, without the addition of hedgerows, trees, and other uncultivated areas, the abundance and diversity of lactating critters was reduced by up to a third.
Agriculture can play another important role for mammals: connectivity. Wildlife-friendly practices like planting grassland or forest strips and diversifying crops on farms can help animals move across the landscape. In turn, this allows gene flow between mammal populations, migration between summer and overwintering habitats, dispersal of individuals into new areas, and range shifts north spurred by global warming. But the context of the diversity matters, Kuipers found. Mammals were more likely to move through agricultural areas surrounded by natural vegetation than development.
Still, some mammals may benefit more than others from diverse farm fields. In his study, Kuipers found that the composition, or the particular set of mammalian species, varied between cropland and natural habitat.
“Even though the average abundance and richness of species is similar in cropland and natural habitats, we also found that the species that do occur there are slightly different,” he told Civil Eats. “So, there is an impact.”
This difference may come down to the type of mammal considered.
Specialist mammals, which occur in only a few specific habitats, were impacted more by the agricultural sites than species that inhabit a variety of habitats, explained Kuipers.
While diversified farm fields have proven to help wildlife, organic agriculture also supports habitat for many species, as it prevents the emission of hazardous chemicals that harm wildlife, along with their prey and habitat.
A good example is Christina Allen’s 10-acre farm in Maryland. With development sprawling across her neighborhood, the property she runs with organic practices with her husband appears to be something of a refuge for mammals.
“We have other critters like skunks, woodchucks, lots of possums, foxes, and even coyotes on occasion,” Allen wrote in an email to Civil Eats. “With development pressure, we notice the poor critters come here as they have to move somewhere . . . but I don’t consider them farm animals; they are wildlife. As long as they do what they do naturally, we coexist with them.”
Fishers, small mammals resembling a cross between a bear and a cat, are another notable appearance on Allen’s farm. Once extirpated from Maryland, they were reintroduced in the 1960s and made a strong comeback in the western part of the state. The fact that Allen’s farm is in eastern Maryland and beyond the lines of their known range shows even rare mammals call their farm home.
This bounty of mammals may have to do with some of their practices. They avoid using pesticides and heavy equipment that could compact the soil, plant flowers in their gardens to attract beneficial insects, and maintain meadows with native plants.
When Mammals Cause Damage
Despite their benefits, mammals can also cause headaches for farmers by eating their crops and farm animals. Organic farmers tend to have a more positive view of wildlife than conventional farmers, who often see them as a problem that needs to be controlled.
“Mammals and humans want to occupy the same landscape,” said Rath. “Because of agricultural expansion that’s increasing conversion of natural ecosystems to ranch land or farmland, we encroach on these natural habitats, and so these organisms come into conflict with us. One of the main examples is the wolf population in the American West—and you have in Montana, Idaho, and California issues with predation of livestock by predators.”
Even Farquhar feels some frustration. “You want to see the mammals thrive, but we’re happy that nature has its own predators for the mammals that would eat our little vegetables,” he said.
In Maryland, Allen had to add extra measures to protect her chickens from predators. “I did have to put huge aviaries up to protect my poultry from coyotes and sometimes a persistent fox,” she wrote in an email to Civil Eats. “The poultry get locked in their big open-air aviaries every night so the wild things can do their thing . . . hopefully, eat mice and rabbits!”
Singh-Varma echoed these sentiments about human-wildlife conflict. “It can directly impact animals through farmers often killing mammals that start to encroach on their agricultural land, especially big predators,” he said. “That’s a common phenomenon and a common problem all around the
There are better ways to protect livestock from predators, however. These include keeping guard animals such as dogs, maintaining areas with food and prey away from the farm, putting up fencing, and providing housing for farm animals as Allen did.
Rath also explained that nonlethal removal and relocation are also options for minimizing conflict.
Supporting Mammals
The world’s need for food is predicted to increase by 60 percent by 2050—and likely won’t stop there, as human population levels are expected to climb until 2080.
As mammals face ever-increasing threats to their existence, diversified agriculture could become increasingly relevant to their survival.
Farmers interested in supporting mammals are in luck. Agencies like the U.S. Department of Agriculture’s Natural Resource Conservation Service promote sustainable agriculture practices benefitting both rural communities and wildlife.
A variety of nonprofit organizations, like the National Wildlife Federation and NRDC, also work with farmers to promote sustainable practices while maintaining and improving wildlife habitat.
“There are enormous benefits to the global environment associated with sustainable agriculture,” Farquhar said from his Maryland farm. “We love what we’re doing.”
Read the original article and see images of some of the mammals mentioned here at Civil Eats.