Subscribe

Latin America

Continental Freshwater Conservation

"Threats to freshwater don't just have local impacts--thy accumulate as you move downstream."

Dr. Paulo Petry, the Conservancy's freshwater specialist in Latin America

There’s a real push-and-pull for freshwater resources in Mexico and Central and South America: growing populations require more electricity that hydroelectric dams can supply; but local populations in rural areas still depend on nearby rivers for drinking water, fishing, and irrigation, and dams can leave them high and dry. 

And then there’s the biodiversity: Brazil’s Pantanal—just like the Everglades but ten times the size—teems during seasonal floods with: jaguars, ibis, river otters, maned wolves, caimans, and thousands of other species. The mineral-rich waters of Mexico’s cenotes (underwater cave systems in the Yucatán Peninsula) nurture an incredible array of algae and are home to unique species of fish

Colombia’s Magdalena River <—an inspiration to Nobel Prize Winner Gabriel García Marquéz—has crazy catfish found nowhere else in the world, and the mighty Amazon—with its pink river dolphins and 15-foot Arapaima fish—also make this part of the world a real treasure to ichthyologists and other freshwater scientists like Dr. Paulo Petry, the Conservancy’s freshwater specialist in Latin America.

Nature.org: I hear you’re quite the fisherman, and that your favorite fishing hole is somewhere in the Brazilian Amazon. Tell the truth: are you really just trying to protect your favorite fishing grounds?

Paulo: I’m interested in everything about fish—I’m an ichthyologist! I like studying them and writing about them, monitoring their populations and protecting their ecosystems, and yes, catching them and releasing them—or sometimes eating them. Even though I like fish, I want to protect fresh water in South America and Central America not just for the fish, not just for fishermen, but for all of us, making sure freshwater ecosystems remain healthy and functional.

Nature.org: What’s the toughest thing about being a freshwater specialist studying the issue across Mexico, Central America and South America?

Paulo: In Latin America, just like around the world, freshwater availability is heterogeneous. In Central and South America, you have some of the rainiest and some of the driest places on Earth. Think about the Amazon rainforest, versus portions of Chile’s Atacama Desert where it only rains once every 150 years.

But freshwater availability also depends on local needs—for example, in Peru and Chile, there’s a lot of stress on water resources because human populations are concentrated in the driest areas—in Peru, for instance, 70% of the population lives where just 1.8% of the country’s water is available. That puts a lot of pressure on water resources and makes it very difficult to maintain the health and diversity of plants and animals that rely on that water. And because industries like mining and agriculture also demand a lot of water, you often wind up with a shortage of water to meet environmental needs. So every part of every country has different needs, and different ways of addressing those needs—which isn’t too different from here in the US.

Nature.org: With dams, deforestation, climate change, increased water consumption, invasive species, agriculture and industry threatening fresh water sources and flows from Mexico to Chile, what are you doing to try and keep freshwater ecosystems healthy?

Paulo: The Conservancy’s conservation framework enables us to work on a systematic basis and at different scales. So we can look at the various threats to various ecosystems, and propose appropriate strategies to abate and mitigate them. We have to look at it from a systemic, holistic perspective, because threats to freshwater don’t just have local impacts—they accumulate as you move downstream.

If ranching and farming are causing erosion that’s polluting a particular river, we work with the farmers and ranchers to limit erosion: we and our partners help them reforest alongside streams on their lands; we help them find ways to keep their cattle off the river banks. If there’s a dam majorly altering an essential river, we can work with dam operators and governments to find ways to let more natural flows be released from the dams at the appropriate times of year.

Nature.org: How many dams are in Latin America?

Paulo: A specific number? It’s impossible to estimate—there are very small ones on small rivers that aren’t even registered by local governments, and there are massive ones like Itaipu in Brazil that provides 20% of the country’s electricity. But across Latin America? There are thousands already in place and at least 2600 in some stage of planning. And since one of the impacts of climate change will be a shift in water supply, it is likely that many more dams will be built to compensate.

Nature.org: Can dams be built in ways that are good for people and freshwater life?

Paulo: Well, there is a new generation of dam and turbine design out there, but there’s still a lot of work to do in terms of gathering evidence that they function as predicted. Our greatest challenge with dams is to make them function as though they weren’t there—closely managing when they release water and how much they release. You have to find a way to nearly mimic a river’s natural rhythms, which is almost impossible to imagine.

If you release too much water at once, for example, and at the wrong time of year, the river might flood, but not in the floodplain where you need it to flood to replicate natural patterns. If you don’t release enough water at the right times of year, flora and fauna suffer because they’re adapted to the natural seasonal flooding patterns.

You have to look at a river from the perspective of the entire river system—you can’t just think about a single portion, or a single dam. Think of a dam as a blood clot in your foot—you can’t just treat the clot locally; you have to cure your entire circulatory system.

Nature.org: You were recently involved in the discovery of a new fish species. How exciting was that?

Paulo: It’s humbling that there are over 12,000 freshwater fish species worldwide and in the Neotropics (Central and South America) the estimates are over 6,000 and counting—not to mention a good reminder that we need to protect our freshwater ecosystems so new species can continue to be discovered, and species we already know about can survive. We’ve made a lot of progress, but for all our knowledge, we know so little about how complex the world’s web of biodiversity really is (Watch a video of Paulo digging for fish in the Amazon mud).

Nature.org: I remember seeing a campaign pushing people to not leave the water running while they brush their teeth. What other kinds of things can a normal person do?

Paulo: Rivers are formed by a very large numbers of drops, and every drop comes from rain or a snowflake, and it runs down a slope to get to you. The water you use has a fundamental property—it’s millions of little drops!—and it can have a real impact. People should not take it for granted that plenty of clean water will always flow.

Nature.org: So much progress needs to be made in order for the world to ensure we have enough water for every person, plant and animal. Do you ever get depressed when you think about how far we have to go?

Paulo: Everyone I know is working really hard on this issue. I’m working really hard on this issue. We can make better decisions about how we use our water, and that will make a difference. It has to. When I have a day off, I want to go fishing. There’s nothing more frustrating than trying to fish a dead river.

What worries me the most is that most of the world has yet to realize how much water is being wasted and contaminated by poor water use practices developed 50 years ago. It’s time for a paradigm shift, and new perceptions and practices that can help us keep water flowing in the face of so many new challenges.

We’re Accountable

The Nature Conservancy makes careful use of your support.

More Ratings