The Rio Grande Valley was once covered in forest. One man is trying to bring it back.
The Tamaulipan thornforest once covered 1 million acres on both sides of the border with Mexico. Restoring even a fraction of it could help the region cope with the ravages of a warming world.
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This story was produced by Grist and co-published with the Texas Tribune.
Jon Dale was 15 and an avid birder when he began planting native seedlings beside his house in Harlingen to attract more birds. He hoped to restore a bit of the Tamaulipan thornforest, a dense mosaic of at least 1,200 plants where ocelots, jaguars, and jaguarundis once prowled among hundreds of varieties of birds and butterflies. Developers began clearing the land in the early 1900s, and Dale's own father bulldozed some of the last coastal tracts in the 1950s.
Today, less than 10 percent of the forest that formerly blanketed the Rio Grande Valley still stands. The U.S. Fish and Wildlife Service has restored 16,000 acres since the 1980s in a bid to protect endangered ocelots, but Dale wanted to do more.
Dale, now 45, is still at it. He is a director at American Forests, which has toiled for 150 years to restore ecosystems nationwide. The nonprofit started working in the Valley in 1997 and took over the federal restoration effort last year. It also leads the Thornforest Conservation Partnership, a coalition of agencies and organizations hoping to restore at least 81,444 acres, the amount needed for the ocelot population to rebound. Although conservation remains the core mission, everyone involved understands, and promotes, the thornforest’s ability to boost community resilience to the ravages of a warming world.
Climate change will only bring more bouts of extreme weather to Texas, and the Valley — one of the state’s poorest regions, but quickly urbanizing — is ill-equipped to deal with it. Dale believes urban thornforests, which can mature in just 10 years, provide climate benefits that will blossom for decades: providing shade, preserving water, reducing erosion, and soaking up stormwater. To prove it, American Forests is launching its first “community forest” in the flood-prone neighborhood of San Carlos, an effort it hopes to soon replicate throughout the region.
“People need more tools in the tool kit to actually mitigate climate change impact,” Dale says. “It’s us saying, ‘This is going to be a tool.’ It’s been in front of us this whole time.”
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The Rio Grande Valley already grapples with climatic challenges. Each summer brings a growing number of triple-digit days. Sea level rise and beach erosion claim a bit more coastline every year. Chronic drought slowly depletes the river, an essential source of irrigation and drinking water for nearly 1.4 million people. Flooding, long a problem, worsens as stormwater infrastructure lags behind frenzied development. Three bouts of catastrophic rain between 2018 and 2020 caused more than $1.3 billion in damage, with one storm dumping 15 inches in six hours and destroying some 1,200 homes. Floods pose a particular threat to low-income communities, called colonias, that dot unincorporated areas and lack adequate drainage and sewage systems.
San Carlos, in northern Hidalgo County, is home to 3,000 residents, 21 percent of whom live in poverty. Eight years ago, a community center and park opened, providing a much-needed gathering place for locals. While driving by the facility, which sits in front of a drainage basin, Dale had a thought: Why not also plant a small thornforest — a shady place that would provide respite from the sun and promote environmental literacy while managing storm runoff?
Although the community lies beyond the acreage American Forests has eyed for restoration, Dale mentioned the idea to County Commissioner Ellie Torres. She deemed it “a no-brainer.” Since her election in 2018, Torres has worked to expand stormwater infrastructure. “We have to look for other creative ways [to address flooding] besides digging trenches and extending drainage systems,” she says.
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Laura Mallonee/Grist
A thornforest’s flood-fighting power lies in its roots, which loosen the soil so “it acts more like a sponge,” says Bradley Christoffersen, an ecologist at the University of Texas Rio Grande Valley. Urban trees can reduce runoff by as much as 26 percent because their canopies intercept rainfall and their roots help absorb it, saving cities millions in annual stormwater mitigation and environmental impact costs. This effect varies from place to place, so American Forests hopes to enlist researchers to study the community forest's impact in San Carlos.
That sentiment has grown as cities across the Valley embrace green infrastructure. Brownsville is planting a “pocket prairie” of thornforest species like brasil, colima, and Tamaulipan fiddlewood in one drainage area. McAllen, about an hour to the west, has enlisted the help of a local thornforest refuge to add six miniature woodlands to school playgrounds, libraries, and other urban locations. The biggest challenge to greater adoption of this approach is “a lack of plant distributors that carry the really cool native thornscrub species,” says Brownsville city forester Hunter Lohse. “We’re trying to get plant suppliers to move away from the high-maintenance tropical plants they’ve been selling for 50 years.”
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American Forests doesn’t have that problem. Two dedicated employees roam public lands to collect seeds, some of which weigh less than a small feather. They typically gather more than 100 pounds of them each year and stash them in refrigerators or freezers at Marinoff Nursery, a government-owned, 15,000-square-foot facility in Alamo that the nonprofit runs.
That may sound like a lot of seed, but it’s only sufficient to raise about 150,000 seedlings. Another 50,000 plants provided by contract growers allows them to reforest some 200 acres. At that rate, without additional funding and an expansion of its operation, it could take four centuries to achieve its goal of restoring nearly 82,000 acres throughout the Valley. “These fields are probably one generation, maximum, from turning into housing,” Dale says.
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Laura Mallonee/Grist
Funding is a serious challenge, though. In 2024, American Forests began a $10 million contract with the Fish & Wildlife Service to reforest 800 acres (including 200 the agency’s job solicitation noted was lost to the construction of a section of border wall). That comes to $12,500 an acre, suggesting it could take more than $1 billion to restore just what the ocelots need.
Despite this, Dale says any restoration, no matter how small, is “worth the investment.” The nursery is currently growing 4,000 seedlings for four more community plots, each an acre or two in size.
For now, nursery workers just have to keep the plants alive. All of them are naturally drought-resistant, and raised with an eye toward the lives they’ll lead. “We don’t baby them or coddle them,” senior reforestation manager Murisol Kuri says. “We want to make sure they are acclimated enough so when we plant they can withstand the heat and lack of water.”
Credit:
Laura Mallonee/Grist
Despite this, on average, 20 percent of plants die, partly due to drought. It underscores the complexity of American Forest’s undertaking: While thornforest restoration can help mitigate climate change, it only works if the plants can stand up to the weather. The organization expects that in the future, species that require at least 20 inches of annual rainfall could perish (some, like the Montezuma cypress and cedar elm, are already dying). That doesn’t necessarily doom an ecosystem, but it does create opportunities for nonnative fauna to push out endemic plants. Removing them is a hassle, so it is best to avoid letting them take root. “If you don’t do this right, it can blow up in your face,” Dale says.
Hoping to evade this fate with its restored thornforests, American Forests has created a playbook of “climate-informed” planting. The six tips include shielding seedlings inside polycarbonate tubes, which ward against strong winds and hungry critters while mimicking the cooler conditions beneath tree canopies. Seedling survival rates shot up as much as 90 percent once American Forests adopted the technique a decade ago.
Another strategy seems abundantly obvious: Select species that can endure future droughts. Christoffersen, the University of Texas ecologist, and his students have surveyed restoration sites dating to the 1980s to see which plants thrived. The winners? Trees like Texas ebony and mesquite that have thorns to protect them from munching animals and long roots to tap moisture deep within the earth. Guayacan and snake eye, two species abundant in surviving patches of the original Tamaulipan thornforest, didn’t fare nearly as well when planted on degraded agricultural lands and would require careful management, as would wild lime and saffron plum.
Credit:
Laura Mallonee/Grist
Altering the thornforest’s composition by picking and choosing the heartiest plants would decrease overall diversity, but increase the odds of it reaching maturity and bringing its conservation and climate benefits to the region. A 40-acre planting at Laguna Atascosa National Wildlife Refuge reveals how quickly this can happen. Five years ago, a tractor wove through the site cultivating sorghum, which gave way to 40,000 seedlings. Today, the biggest trees stand 10 feet tall, with thorns high enough to snag clothing.
This little patch of the past does more than preserve the region’s biological history or defend it from a warming world. It’s an attempt to reverse what naturalist Robert Pyle calls an “extinction of experience.” Most people have never even heard of a thornforest, let alone witnessed its wild beauty at Santa Ana. Dale and those working alongside him to revive what’s been lost want others to know the value this ecosystem holds beyond saving ocelots or mitigating climate change. His grandfather was a preacher, and that influence is evident as he speaks of the “almost transcendental” feeling he gets simply being in nature. “I’ve talked to people, and it’s like, ‘Do you know how this is going to enrich your life?’”
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