Image source, Scientific
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- author, Becca Warner
- Author title, BBC Future
In the dusty Chihuahuan Desert of central Mexico, cold, dark caves hide among brown rocks. Inside, in late spring, thousands of little hairy bats congregate. Most of them are female and pregnant, making the 1,609-kilometre journey from southern Mexico to the southwestern United States to give birth.
They are hungry and fly for hours at night to find enough food. They fly from one plant to another, collecting nectar and dispersing pollen as they move.
Among her favorites are the delicate yellow flowers of the aloe vera plant, which appear only once during the decades of the plant’s life. These cactus plants, with spiky leaves, have a long history in Mexican culture. They are used to make syrup, ropes and soap, and their juice is the main ingredient in one of Mexico’s most emblematic products: tequila.
But wild cacti are in decline: in a study of 168 species, 42 are threatened or critically endangered. This means less food for the bats that depend on its flowers, and fewer bats in turn means fewer cactus plants being pollinated.
To break this cycle, conservationists are working with local residents to plant thousands of agave plants, helping to feed bats and protect the future of tequila production in Mexico.
One species of cactus-dependent bat, the lesser cactus bat, has seen a remarkable population rebound in recent decades, doubling from 1,000 specimens in 1988 to an incredible 200,000 today. However, other species are not.
The population of long-tailed bats has declined by approximately 50% in the past two decades and is currently in danger of extinction.
Image source, Horizonline Photos/Bat Conservation International/Ruben Galicia
Biologist Marco Antonio Reyes Guerra is part of the project Bat friendly From the National Autonomous University of Mexico (UNAM), which collaborates with farmers to encourage the cultivation of cacti that favor bats. He explains that many of the threats bats face are caused by humans.
“If they experience any disturbance in the caves, they will abandon them and lose their home. People are deforesting several areas of dry forest, and in that forest there are species that bats use as a food source.”
These species include cactus, in addition to other plants that bats feed on.
Interdependence
Bat Conservation International (BCI) scientists are determined to turn things around for this declining species. The Cactus Restoration Initiative consists of planting and protecting wild cacti in the “nectar corridor” that bats follow on their migration.
“This all started because once these migratory species leave central Mexico, they depend largely on agave,” says Ana Ibarra, a bat biologist and BCI regional director.
Wild agaves face their own threats: they are harvested for alcoholic beverages, grazed by livestock, losing habitat to agriculture, and facing drier conditions due to climate change; In addition, because there are fewer bats, the plants are pollinated less frequently.
Agave depends on bats for reproduction, just as hungry bats depend on agave for food.
Image source, Getty Images
“Bats and agave have evolved together for many millions of years,” says Reyes Guerra. With their long tongue and long snouts, bats can reach the narrow cone flowers of cacti to feed and collect pollen on their faces and fur. “If bats were not present in the ecosystem, the cactus would likely not produce seeds to reproduce, because cacti only reproduce once in their lives.”
Without intervention, and in the face of climate change, scientists estimate that endangered bat species will be 75% less able to access agave nectar in 2050 than today.
For conservation efforts to succeed, agave must be given the opportunity to grow large enough to flower, not just for the bats, but for them as well.
Growers who grow agave for tequila often cut the stem to prevent flowering, resulting in a larger “heart” (or piña) of the harvest.
Image source, Horizonline Photos/Bat Conservation International
Instead of reproducing by pollination, these plants produce “seedlings,” which are genetic clones of the parent plant. This reduces the genetic diversity of species, making them less resistant to the drier conditions that accompany climate change, as well as pathogens and pests.
“It’s a huge risk to the agave and mezcal industry,” says Reyes Guerra. Ultimately, to survive as a species, cacti need to be pollinated.
“Without bats, tequila and mezcal would not exist,” Reyes Guerra adds. “If people want to keep drinking tequila and mezcal, they have to take bats into account, and they have to worry about their conservation.”
Teamwork
Since launching the Agave Restoration Initiative in 2018, the team and local communities have planted more than 180,000 native agave plants and planted more than 150,000 plants from seed in nurseries in Texas, Arizona, New Mexico and throughout Mexico.
Reyes Guerra’s bat-friendly tequila and mezcal project is also working to increase the number of yellow agave flowers in southwestern Mexico.
Participating growers allow at least 5% of their agave plants to mature and flower, so passing bats can feed. The alcoholic beverages produced by this farm are considered “bat-friendly,” and so far 300,000 bottles of “bat-friendly” tequila and mezcal have been produced.
It’s not just farmers who determine the future of bats and agave. In Mexico, 53% of the land is community property, meaning that any conservation effort must include everyone who lives on it.
“From the beginning, it was very clear that we needed to work with communities and try to meet the needs of both bats and humans,” Ibarra says.
Image source, Getty Images
The first step was to teach people that nectar-feeding bats are not harmful. People often think they are vampire bats, which can transmit rabies. According to Ibarra, some locals burn caves with bats “without knowing whether they are really vampire bats.”
Lisette Lequin is the director of the Flora and Fauna Conservation Area of Sierra La Mugonera, a natural space protected by the federal government in Mexico that collaborates with the Agave Restoration Initiative. Work closely with local people to change people’s perception of bats.
“In the past, people hated bats and tried to kill everyone they saw,” he says. But today, thanks to the educational program offered by BCI, people are actively protecting the caves.
“They don’t let anyone come in and do anything that could harm the bats,” Lequin says. “Almost everyone really loves bats. They realize that bats are a wonderful source of many benefits.”
Image source, Getty Images
Communities across Mexico now protect six important places from wild bats, and the initiative’s education program has reached more than 1.5 million people.
Reyes Guerra agrees that bat conservation starts with local people.
“Conservation cannot take place without taking the local people into account and without consulting them to make decisions, because sometimes they have very valuable information that we as scientists do not know,” explains Reyes Guerra, who was recently guided to a small, inaccessible cave that houses five species of bats. “It’s a very rare thing to find,” he points out.
However, the real impact of recent conservation efforts will not be felt until a few years later, as agave needs time to grow. But thanks to BCI and the project Bat friendlypeople let more aloe vera plants mature and flower.
“You can see patches of flowering cacti in areas where you couldn’t see anything before, because people are now leaving the flowering stems for the bats,” Ibarra says.
He adds that he has already detected an increase in the number of baby bats: “These increases are not big jumps, but they are steady. When a sustained decline is observed, just keeping the numbers stable is a huge victory.”
Lequin noticed that in places where aloe vera was planted, the landscape began to look a little greener. “You can see more wildlife because they have food and places to hide.”
There is still time to create an abundant and thriving trail of agave nectar. But until then, Reyes Guerra points out, the bats will need more help.
“The problem with reforestation using only agave is that bats feed on several species. So, if we plant agave only to feed bats, it will not be enough.” Other important species are ceiba trees, ipomoea trees and cacti such as the saguaro.
Restoring the cactus population is just the first step in creating a healthy ecosystem where more plants and more bats can thrive. Humans are an important part of this ecosystem, Lequin says, and they benefit when bats are healthy. “Taking care of bats here benefits people and the ecosystem. In fact, everything is interconnected.”
And if a life well lived includes tequila, whether as agricultural income or as a nightcap, then desert landscapes filled with noisy, swooping creatures and thriving life benefit us all.
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