The Student News Site of University of Arizona

The Daily Wildcat

86° Tucson, AZ

The Daily Wildcat

The Daily Wildcat


    Biosphere 2 researchers research climate change in Arizona’s only rainforest


    Courtesy of Patrick O’Connor

    A vine descends from the dense canopy of Biosphere 2’s tropical rainforest biome. Experiments in this artificial rainforest give researchers insight into how ecosystems will respond to climate change.

    Most days, you’ll find Joost van Haren tromping through Arizona’s only tropical rainforest.

    An assistant research professor at the UA, van Haren works in the rainforest at Biosphere 2—in the middle of the Sonoran Desert, about 30 miles north of Tucson. Under the glass-and-steel dome of this 3.14-acre, space-age research facility, van Haren can turn off the rain or adjust the amount of carbon dioxide in the air.

    The rainforest biome is an important laboratory for scientists studying climate change. To observe how plants will react as global temperatures rise, van Haren and his team simulated a drought in Biosphere 2’s rainforest over the summer of 2014.

    Biosphere 2 is also being used to understand how the rainforest contributes to global warming. The researchers are monitoring how methane, a greenhouse gas that traps 25 times more heat than carbon dioxide, is produced in the rainforest. This summer, they will take the methods and equipment they tested in Arizona to the dense peatlands of Peru to study how methane flows through a natural environment.

    “At [Biosphere 2], you have a magnifying glass on how interactions between the [environment] and atmosphere works,” van Haren said.

    Just add water

    Van Haren’s office at the UA is sparsely decorated; he said he doesn’t like to spend time indoors. Originally from the Netherlands, he became interested in environmental science as a kid watching Jacques Cousteau explore the underwater world. Van Haren studied Earth sciences as an undergraduate at Utrecht University so he could work in the field.

    Van Haren earned his doctorate in 2011 at the UA, where he worked in Biosphere 2’s rainforest biome as well as at field sites around the world.

    One of van Haren’s favorite places is the Amazon rainforest, which he predicts will become drier with climate change. Some researchers have even predicted that one day it will turn into the Amazon savannah.

    To understand how tropical forests will respond to an arid environment, van Haren and his team recently simulated a drought in the Biosphere rainforest by turning off all the sprinklers that simulate rainfall for two months.

    The trees slowly shed their leaves to ensure that they could effectively use the scarce remaining water. During the hot part of the day, the plants closed the tiny pores on their leaves that allow water and carbon dioxide to move in and out.

    These adaptations led to a high survival rate among most species. “These trees are very resilient,” van Haren said.

    Computer simulations of the Amazon rainforest created by other scientists predicted that many species of plants would die during a drought. The Biosphere 2 rainforest outperformed what the models predicted, but it is not a perfect copy of the Amazon. It would be difficult to make a perfect model that would replicate all the complex interactions among plants, animals and microorganisms.

    The results of the drought experiment will help other scientists adjust computer models that predict the effects of climate change all over the world.

    “It’s oftentimes easier to run an experiment in Biosphere 2 and then take it to the real world because we have much greater detail in the data,” van Haren said.

    Roots of the rainforest

    Although Biosphere 2’s rainforest may not truly represent a natural forest, it’s a great compromise for researchers who prefer not to share their sleeping bags with jungle snakes.

    “It’s always a simplification of the real world, but it helps us understand how the real world works,” van Haren said.

    Biosphere 2 began its life as an experimental laboratory in 1991, when eight biospherians were sealed inside the gigantic greenhouse. They were given no food, water or oxygen other than what they could provide for themselves from the diverse biomes inside.

    Today, Biosphere 2 provides a large, enclosed space where scientists can conduct research that is impossible or inconvenient to do in the field. They can also test equipment to see if it will withstand the unforgiving humidity, extreme temperatures and constant precipitation of the rainforest before deploying it for costly field research. If problems arise, ordering replacement parts from Biosphere 2 takes days instead of the weeks needed to ship something to the Amazon.

    From gas to global warming

    The Biosphere’s 6,500 windows form a unique laboratory. Thanks to these windows, ultraviolet light is filtered out, which normally produces unstable molecules called free radicals in the atmosphere. In the natural world, free radicals quickly react with methane to produce a variety of byproducts that contribute to global warming but are hard for scientists to track.

    By running experiments at Biosphere 2, van Haren and his team can monitor exactly how methane is exchanged between the atmosphere and the rainforest without the risk of change via free radicals.

    “Methane and other greenhouse gases insulate heat in our atmosphere, which keeps the planet warm,” said Caitlynn Kestler, a criminal justice studies senior who interned for van Haren. “An abundance of these gases contribute to global warming.”

    Van Haren and his colleagues received more than half a million dollars from the National Science Foundation in May 2014 to research methane in the sparsely studied Peruvian peatlands. Because methane traps 25 times more heat than carbon dioxide, van Haren hopes to understand how methane flows through the environment and how the peatlands affect climate change.

    In summer 2014, van Haren and his team traveled to Peru to study how plants regulate methane. Van Haren traversed the muggy wetlands with a supply of instruments he had made to capture gases released by trees. After attaching these instruments to different trees, he found that palm trees release much more methane than other trees.

    Methane is produced by a variety of sources, but microorganisms are a major contributor. Certain microorganisms produce methane by breaking down fallen plants into the organic mush that is common in Peruvian peat. Plants like palm trees may act like giant drinking straws that suck out the methane trapped in the peat, van Haren said. When a palm tree absorbs water through its roots, gases trapped in the water and soil travel up the plant and escape through pores in the stems and leaves.

    Unfortunately for van Haren, his homemade equipment was a tasty target for termites. He had to cut his fieldwork short.

    “[Working in Peru last August] was the hardest fieldwork of my life,” van Haren said. “Working in the swamps was very, very tough.”

    Van Haren and his team returned from Peru with a mountain of data and some termite-mangled equipment. Over the next few months, they analyzed the data and worked out the bugs in their equipment to prepare for their December 2014 trip.

    Although the team was more experienced, the trip was far from easy.

    “[The December trip] literally whooped my heinie,” van Haren said.

    The trip was worth the pain, as van Haren and his team confirmed their previous findings. They found that most of the methane is being released near the bottom of the palm tree, which leads van Haren to believe that the methane trapped in the soil is traveling up the palm trees’ roots.

    Van Haren also believes that he may have an explanation for why other trees are not acting like methane vents. The palm trees he studied have aerial roots, which are found all over the trunk instead of just under the soil.

    When a palm tree loses an aerial root, a hole leads to the inner portion of the plant’s water transport system called the xylem. When van Haren plugged these holes, he found an “immediate reduction” in the amount of methane produced.

    Van Haren continues to travel to Peru every year and hopes to find a method for measuring methane inside the palm tree’s xylem to confirm his hypothesis.

    Follow Patrick O’Connor on Twitter.

    More to Discover
    Activate Search