Chapter Introduction
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CHAPTER 8
ECOSYSTEMS AND NUTRIENT CYCLING
ENGINEERING EARTH
An ambitious attempt to replicate Earth’s life support systems falls short
CORE MESSAGE
Ecosystems are complex assemblages of many interacting living and nonliving components. Living organisms play irreplaceable roles in nature, supporting life and allowing ecosystems to function over the long term. It is important that we protect and work to restore ecosystems in nature to keep these connections intact so that we and other species can continue to live and thrive on this planet.
AFTER READING THIS CHAPTER, YOU SHOULD BE ABLE TO ANSWER THE FOLLOWING GUIDING QUESTIONS
1 What is the hierarchy of organization recognized by ecologists, and why might it be useful to recognize such distinctions?
2 Why do ecosystems need a constant input of energy? How do they deal with the fact that Earth does not receive appreciable new inputs of matter?
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3 What are biomes, and how do environmental factors affect their distribution and makeup?
4 What is a population’s range of tolerance, and how does it affect the distribution of a population within its ecosystem or its ability to adapt to changing conditions?
5 How do carbon, nitrogen, and phosphorus cycle through ecosystems? How are these cycles being disrupted, and what problems can this disruption cause?
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On September 26, 1993, with their first mission complete, four men and four women emerged from Biosphere 2—a hulking dome of custom-made glass and steel—back into the Arizona desert, where throngs of spectators stood cheering. they had been sealed inside the facility, along with 3,000 other plant and animal species, for exactly 2 years and 20 minutes; it was the longest anyone had ever survived in an enclosed structure.
The feat was part of a grand experiment, the goals of which were twofold. First, scientists wanted to prove that an entirely self-contained, humanmade system—the kind they might one day use to colonize the Moon or Mars—could sustain life. Second, they hoped that by studying this mini-Earth, which could be controlled and manipulated in ways the real Earth could not, they might better understand our own planet’s delicate balance and how best to protect it.
Despite the fanfare surrounding the biospherians’ emergence, it was tough to say whether the mission had been a success or a failure. More than one-third of the flora and fauna had become extinct, including most of the vertebrates and all of the pollinating insects. Morning glory vines had overrun other plants, including food crops. Cockroaches and “crazy ants” were thriving. Too little wind had prevented trees from developing stress wood—wood that grows in response to mechanical stress and helps trunks and branches shift into an optimal position; without stress wood, the trees were brittle and prone to collapse. And eating too many sweet potatoes had turned the biospherians themselves bright orange. (A string of plant diseases had decimated other crops.)
On top of that, nitrous oxide (laughing gas) had grown concentrated enough to “reduce vitamin B12 synthesis to a level that could impair or damage the brain,” according to one interim report. And oxygen levels had plummeted from 21% (roughly the same as Earth’s atmosphere) to 14% (just barely enough to sustain human life). To fix this, project engineers had been forced to pump in outside air, violating the facility’s sanctity as a closed system.
Worst of all, missteps and course corrections had been mired in secrecy—each one leaked to the press only months after the fact. Rumors had begun to circulate that the eight people sealed inside—not to mention the ones they took their orders from—were more interested in creating a futuristic utopia than in conducting rigorous scientific research. As evidence for this rumor mounted, the scientific community grew suspicious. Was Biosphere 2 legitimate science, a publicity stunt, or some bizarre mix of the two?
To be sure, the eight biospherians had survived, and many experts agreed that, in principle at least, the facility still held enormous potential as a scientific tool. But before that potential could be realized, the scientific community and the public at large would need to know exactly what had happened inside the desert dome.
To answer that question, we need to answer a few others first: What exactly is a biosphere, and just how did Biosphere 2’s creators set about building one?