Ecology Without Wilderness: Tending the Global Garden We Call 'Nature'

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In Hawaii, the lush tropical plants out the hotel window looked gorgeous, but I knew that many of them had been introduced by people and were now considered a threat to the native species. I also knew that Hawaii has been called "the extinction capital of the world," and that a whole list of beautiful birds are either gone or near gone. And yet the islands are thick with conservationists who have not given up on the ideal of Hawaii as it once was.

My first stop was a group of experimental field plots testing the feasibility of restoring lowland forests on the Big Island's wet side. The plots are hidden in a forest on the Hawaii Army National Guard Keaukaha Military Reservation. Growing on flat land with plenty of rain, most forests of this type had been cleared for agriculture. What was left, or what grew back, is now dominated by plants from places other than Hawaii.

Today half of the plants in Hawaii are nonnative. In many lowland forests only the large trees are native; under them grows a carpet of introduced seedlings, just waiting for the day the giant natives fall.

Rebecca Ostertag of the University of Hawaii at Hilo explained why these "invaders" are so prevalent on Hawaii. Hawaiian plants, having evolved in isolation for up to 30 million years, generally grow slowly and use resources less efficiently than continental plants, which evolved with more competition. Similarly, Hawaiian birds and animals are mostly helpless against introduced diseases. Avian malaria has knocked off many bird species; there were no mosquitoes on the islands until recently, so birds there never evolved any defenses to the mosquito-borne disease. Hawaiian raspberries and roses have even lost their thorns, and Hawaiian mints their minty defense chemicals, because there were no plant-eating animals around to fend off. Such mellow Hawaiian species are pushovers for the scrappier mainland species that humans brought to the islands. Today half of the plants in Hawaii are nonnative. In many lowland forests only the large trees are native; under them grows a carpet of introduced seedlings, just waiting for the day the giant natives fall. Some ecologists call such places "forests of the living dead."

At the army base, mynah birds from Asia stood in the road. The air was soft and humid. Ostertag and I met up with her colleague, Susan Cordell of the U.S. Forest Service, and a graduate student named Joe Mascaro from the University of Wisconsin, Milwaukee. Together we headed out to the study plots. After hopping a fence intended to keep out feral pigs, we pushed through a jungle of foliage from everywhere: trumpet tree with its huge star-shaped leaves, a native of Mexico, Central America, and Colombia; bingabing, a small tree with big parasol-like leaves, from the Philippines; tasty strawberry guava, from the Atlantic Coast of Brazil; purple-flowered Asian melastome; "Koster's curse," a little shrub originally from Mexico and parts of South America; and albizia, another immigrant from Southeast Asia. Many of these species were introduced not only deliberately but methodically--aerially seeded in the 1920s and 1930s after large forest fires to prevent erosion. The experts figured that Hawaiian plants would grow too slowly to do the job effectively. The resulting cosmopolitan forest is green and dense, with creepers hanging everywhere. Underfoot, dead leaves like starched, crumpled brown napkins made a terrific crunch.

Suddenly we stepped into a clearing. Here plants were spaced widely apart, with black lava rock covered in chartreuse moss visible in between. This was one of the study plots: small squares in which every single non- native plant had been ripped out by hand. To get these spaces to a purely native state, researchers had to pull up and remove almost half the vegetation, a process that took about a week's worth of labor per thousand square feet for the initial clearing and epic bouts of weeding thereafter. As a result, the plots look a bit sad and empty, like someone's living room in the middle of a move-out.

Here, I could get a better look at the typically less showy Hawaiian natives, including tree ferns; lama, a hardwood in the ebony family; the vaguely Mediterranean-looking 'ohi'a tree with feathery bunches of bright red stamens; and the sweet-smelling maile vine, used for making fragrant leis.

The plots weren't created to be showplaces, however, but as experiments to see whether a native Hawaiian forest would bounce back if all the introduced species were removed. With all those aggressive tropical invaders exiled, would the native flora tap into the soil nutrients, rain, and newly available sunlight and grow vigorously to fill up the space? When I visited, it had been five years since the experiments began. Disappointingly, the mature native trees had grown very little. As Ostertag and Cordell put it, "The native trees may either be responding to the treatments very slowly and still undetectably, or they may be unable to respond at all." The researchers were pleased, however, to see quite a few native seedlings appear on the sun-dappled forest floor.

These removal plots were weeded out for a specific experiment. But they also represent, in miniature, what many conservationists would love to do for huge swaths of the planet: rip out the introduced species, make way for the natives, and return the area to the way it used to be, making the baseline the goal.

But their baseline just isn't achievable without spending a huge amount of money and time. "I think that people that are interested in protecting Hawaii's flora and fauna have resigned themselves to it being in postage-stamp-size reserves," said Cordell, sadly.

Of course, Osterag and Cordell's forest is in particularly bad shape. But are ecosystems that aren't so trashed perhaps redeemable? The answer is no, at least not in Hawaii. As we thrashed through the nonnative-dominated forest that encircled the weeded plots, Ostertag and Cordell mostly saw failure. But Joe Mascaro, the grad student who accompanied us, saw something less value-laden. He saw the future, and as an ecologist, he found it interesting. He saw plants interacting together in new ways, with new creatures dispersing their seeds, new competitions for resources. He expects that there will be some casualties when species come in contact for the first time--"local extinctions and whole ecosystem types that will evaporate," he predicts--but he does not expect that the resulting ecosystems will be worthless just because they are changed. They will still store carbon in the bodies of their trees, keeping it out of the atmosphere where it would contribute to global warming. They will still harbor many species. They will still smell cool and green. At the very least, he says, they should be studied, because they are probably more representative of today's Earth than any so-called "pristine" forest. "These ecosystems, like it or not, are going to be driving most of the natural processes on Earth," he says.

We are already running the whole Earth, whether we admit it or not. To run it consciously and effectively, we must admit our role and even embrace it. We must temper our romantic notion of untrammeled wilderness and find room next to it for the more nuanced notion of a global, half-wild rambunctious garden, tended by us.


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Excerpted from Emma Marris's Rambunctious Garden: Saving Nature in a Post-Wild World (Bloomsbury USA)


Image: Plot in Hawaii with all non-native species removed. Emma Marris.

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Emma Marris is a freelance writer based in Columbia, Missouri. Her stories have appeared in Wired, Conservation, and Nature.

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