For over 20 years, our American ReLeaf program has been planting native trees to restore thornforests in the Lower Rio Grande Valley, located on the border of Texas and Mexico near the Gulf Coast.
This ecosystem is unlike any other in the United States. It’s home to an incredibly diverse group of plants and animals, including the critically endangered ocelot. But with less than 10 percent of thornforests left, these landscapes and their wildlife are in danger of disappearing.
What Is a Thornforest?
Thornforests, also known as Tamaulipan thornforests or thornscrub, don’t look like a typical woodland. They’re dense and shrubby, adapted to the region’s extreme heat, droughts and low rainfall.
These are tough growing conditions. In some areas, even the biggest trees, such as mesquite and ebony, are no taller than 6 or 7 feet. Despite this harsh environment, 1,200 native plant species flourish in thornforest habitats.
Thornforests Face Severe Threats
Thornforests used to cover almost the entire stretch of the Lower Rio Grande Valley. Now, less than 10 percent of these forests remain. Historically, land clearing for ranches and farms was the main driver of deforestation in this region. Now, new and old threats present severe risks to thornforest survival:
- Manufacturing and trade with Mexico have transformed the Lower Rio Grande Valley into one of the most rapidly urbanizing parts of the country. Urbanization is swiftly paving over unprotected patches of thornforest, as well as areas suitable for reforestation.
- The construction of the border wall is destroying habitat and making it hard for animals to migrate between thornforest patches.
- Climate change is triggering increasingly extreme heat and droughts, along with violent, unpredictable storms and flooding. Many plant and animal species that currently live here may not be able to survive in the future.
- The Rio Grande is the main source of water for cities, towns and farms in the region. As a growing population drives ever-greater water extraction, some thornforests don’t have enough water to survive.
- Invasive grasses and trees, like Guinea grass, are crowding out native plants and preventing them from growing. These invasives are also far “thirstier” than native plants. They suck up groundwater and further dry out the landscape.
Why Thornforest Reforestation Is Important
Thornforests Are Home to Hundreds of Species of Rare and Unique Animals
Thornforests are one of the most biodiverse ecosystems in the United States. These landscapes are home to 530 species of birds, 300 species of butterfly and 11 threatened and endangered species including Texas tortoises, jaguarundis and ocelots.
Ocelots, which look like miniature jaguars, are critically endangered in the U.S. Only around 50 ocelots are left in the country, and they all live in the Lower Rio Grande Valley. Because their habitat is so fragmented, they have to travel through busy urban areas to find food and mates. Sadly, the main cause of death for these rare cats is vehicle collisions.
Protecting and Restoring Thornforests Safeguards the Water Supply
Most thornforest reforestation is done on former agricultural land. Taking farmland out of production means that less water is withdrawn from the Rio Grande for irrigation — a big benefit in a region where there’s often not enough water to go around. Dense thornforest vegetation also helps to absorb and filter water when storms flood the Rio Grande.
Thornforests Are Good for the Economy
Thornforests draw millions of birdwatchers each year to view spectacular hawk migrations and tropical birds like green jays and Altamira orioles. In 2014, ecotourism generated more than $340 million in the Lower Rio Grande Valley.
How We Are Reforesting the Lower Rio Grande Valley
We Lead Research and Develop Tactics to Help Forests Withstand Climate Change
Over the last 22 years, American Forests has planted more than 2 million thornscrub trees and other native plants across more than 4,000 acres of former agricultural land in the Lower Rio Grande Valley. Our reforestation innovations include:
Planting species that will be able to better withstand future conditions
Climate change is altering the Lower Rio Grande Valley so swiftly that some plants will not be able to survive in certain areas in the future. At each reforestation site, we plant a diverse array of native species that are better adapted to future conditions like increasing drought.
Selecting and growing genetically diverse seeds
We collect seeds across the Lower Rio Grande Valley from a wide variety of individual plants. This ensures that our seedlings are genetically diverse. Diverse plant genetics are important as climate change makes future conditions ever more unpredictable. For example, certain populations of a given thornforest tree species may prove to have higher drought tolerance than others. Collecting and raising seedlings from these populations is critical for boosting the region’s natural capacity for adaptation.
Site preparation tactics that help native plants outcompete invasive species
Reforestation in the Lower Rio Grande is a constant battle against invasive plants like Guinea and buffel grass. We carefully prepare planting sites by using machinery, selective herbicide applications and/or controlled fires to clear away invasives that would otherwise overrun new plantings.
Seedling shelter tubes that dramatically increase plant survival
We plant seedlings in reusable plastic tubes that protect the young plants from drying out in the region’s hot, dry winds. The moisture retention provided by the tubes also encourages seedlings to grow tall and develop deep roots, which helps them outcompete invasive species. In some cases, these tubes have boosted two-year seedling survival rates from less than 10 to over 90 percent.
We Work with Local Partners to Protect Thornforest Biodiversity
American Forests formed the Thornforest Conservation Partnership in 2018 to develop science-based conservation plans and goals for the entire Lower Rio Grande Valley. The partnership also educates the public about the importance of thornforests, and encourages action for stronger public policies and funding. The Thornforest Conservation Partnership is a coalition of state and federal agencies, universities, nonprofits and community organizations.
The Thornforest Conservation Partnership identifies potential thornforest restoration sites that will have the biggest positive impact for the region’s unique wildlife. The ultimate goal is to reforest areas in between existing thornforest patches. These forested “corridors” will help ocelots and other animals travel more freely and safely.
Our Projects in the Lower Rio Grande Valley
La Sal del Rey Reforestation Project Uses Innovative Drought Resilience Planting Tactics
La Sal de Rey lake, with glittering salt deposits that were once mined by the Aztecs and Spanish, is bookended by the Lower Rio Grande Valley National Wildlife Refuge to the south and working ranches to the north. This March, American Forests worked with the U.S. Fish and Wildlife Service and the Wildlife Conservation Society’s Climate Adaptation Fund to plant 70,000 seedlings of 31 thornforest species on 70 acres of former farmland.
This project is the first to use American Forests’ drought resilience strategy. We used tactics like planting seedlings in shelter tubes and using a genetically diverse variety of drought-resistant plants to help the reforested site withstand a hotter, drier future. We are working with our partners to expand this strategy to upcoming thornforest restoration projects.
Thornforest Conservation Partnership Launches Conservation Plan for the Lower Rio Grande Valley
A properly designed conservation plan can help make sure that limited resources are efficiently used to protect and restore the most ecologically important places. But until recently, there was no comprehensive conservation plan to guide thornforest protection and reforestation in the Lower Rio Grande Valley.
To address this shortfall, American Forests and our partners completed the Thornforest Conservation Plan in February, which aims to spark a coordinated, regional response to thornforest conservation. The plan identifies core areas of existing thornforest habitat, potential corridors that link habitats together, and potential habitat restoration opportunities throughout the Lower Rio Grande Valley and neighboring areas.
Discover how two cats from very different habitats share an unlikely connection through the Rio Grande River and their need for forest restoration.
Read about the diverse group of partners working to restore thornscrub forest in the Lower Rio Grande Valley of Texas.