“Nature is almost everywhere. But wherever it is, there is one thing nature is not: pristine,” writes science journalist Emma Marris in her engaging new book Rambunctious Garden: Saving Nature in a Post-Wild World. She adds, “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.” Marris’ message will discomfort both environmental activists and most ecologists who are in thrall to the damaging cult of pristine wilderness and the false ideology of the balance of nature. But it should encourage and inspire the rest of us.

Marris begins by exposing the vacuity of the notion of the ecological baseline. “For many conservationists, restoration to a pre-human or a pre-European baseline is seen as healing a wounded or sick nature,” explains Marris. “For others, it is an ethical duty. We broke it; therefore we must fix it. Baselines thus typically don’t act as a scientific before to compare with an after. They become the good, the goal, the one correct state.” What is so good about historical ecosystems? I too have noted that ecologists when asked this same question become almost inarticulate. They just know that historical ecosystems are better.

So many ecologists set the historical baseline as the condition of ecosystems before Europeans arrived. Why? The fact is that primitive peoples killed off the largest species in North and South America, Australia and Pacific Islands thousands of years ago. For example, after people showed up about 14,000 years ago, North America lost 60 or so species of tasty mammals that weighed over 100 pounds, including giant ground sloths, mammoths, mastodons, cheetahs, camels, and glyptodonts.

Marris argues that the cult of pristine wilderness was created by nature romantics like John Muir. Muir is famous for advocating that the Yosemite Valley be turned into a national park. As Marris notes, wild nature for Muir was a necessity for “tired, nerve-shaken, over-civilized people” suffering from “the vice of over-industry and the deadly apathy of luxury.” And for some people it might be—but that is not a scientific claim about ecosystems and their “integrity.”

In fact, Marris reports that there is precious little scientific support for the ideology that pristine nature is somehow “better” than the mélange that humanity has created by moving species around the globe. For example, she visits Hawaii where half of the plant species now living on the islands are non-native. One brave younger ecologist, Joe Mascaro, studies novel ecosystems that are developing on Hawaii that incorporate both native and non-native species. Among other things, Mascaro “found that the novel forests, on average, had just as many species as native forests” and “that in many measures of forest productivity, such as nutrient cycling and biomass, novel forests matched or outproduced the native forests.”

Marris contrasts Mascaro with another ecologist, Christian Giardina, who helps manage the Laupahoehoe Natural Area Reserve in Hawaii from which he wants to extirpate non-natives. Yet even Giardina muses over dinner, “Are we so religious about this biodiversity ethic that we need to be called on it?” He answers his own question: “If you really dig down to why we should care, you end up with nothing. You are running on faith that we should care.”

Although Marris doesn’t cite him, she is plowing much the same intellectual ground as University of Maryland philosopher Marc Sagoff. Sagoff has challenged ecologists to name any specifically ecological criterion by which scientists can objectively determine whether an ecosystem whose history they don't know has been invaded or not. Are invaded ecosystems less productive? No. Are they less species-rich? No. And so on. In fact, Sagoff points out that there is no objective criterion for distinguishing between "disturbed" ecosystems and allegedly pristine ones.

Marris also cites research that shows that the notion of the “balance of nature” is scientifically specious. Early in the 20th century influential ecologist Frederic Clements developed the theory that each ecosystem tended toward a stable climax that, once achieved, was perfectly balanced unless disturbed by people. Each participant in the climax ecosystem fitted tightly into niches as a result of coevolving together. However, ecologist Henry Gleason, a contemporary of Clements, countered that ecosystems were assembled by chance just depending on what species got there first and were successful in competing with other species as they arrived. For the most part, 20th century ecologists fell into the Clements’ camp.

Now we know now that Gleason was far more right than Clements—ecosystems are largely assembled by chance. For example, northern temperate forests are composed of an assemblage of species that mixed together as they raced northward out of various refugia as the glaciers retreated.

Although Marris mentions it briefly, one of the more fascinating novel ecosystems is the accidental rainforest created on Ascension Island in the middle of the Atlantic Ocean. A little over 150 years ago, the British navy began receiving shipments of trees and shrubs from all over the world from the collections at Kew Gardens in London. Once planted, they took hold and have transformed the bare peak once known as White Mountain into Green Mountain today. Species don’t need to coevolve to create fully functioning ecosystems [PDF]; they make the best of what they have.

Only when the ecologically-correct ideologies that blind us are upended can we can see the real nature that is all around us. Baselines are properly transformed into aesthetic choices rather than “scientific” mandates. For example, Marris discusses the ambitious Pleistocene Rewilding proposal in which proxy wild species from Africa might be used to replace those North American species killed off by early peoples. African cheetahs might chase after pronghorns, and elephants graze where mastodons once did.

A small version of rewilding is the fascinating Oostvaardersplassen [PDF] experiment where researchers are designing an ecosystem that aims to mimic what Northern Europe might have looked like 10,000 years ago. It is stocked with herds of Konik horses and Heck cattle, thought to be respectively similar to the tarpan horses and the aurochs that once roamed Europe. The newly constructed ecosystem has attracted many wild species that have long been absent from the Netherlands. It is still missing predators, but wolves are apparently moving westward from Eastern Europe.

Marris argues that the conservation and appreciation of nature can take place at far less exotic locations, such as backyards, city parks, farms, and even parking lots. If biodiversity is what is of interest, she notes that the Los Angeles area is home to 60 native tree species, but now hosts 145 species. “With eight to eleven tree species per hectare, L.A. is more diverse than many ecosystem types,” she writes. Another researcher has identified 227 species of bee living in New York City. And if some of us choose to conserve some areas as “pristine” with regard to some preferred aesthetic baseline, that’s O.K. Certainly science can be used to help achieve that goal, but such areas become essentially wilderness gardens maintained by “perpetual weeding and perpetual watching.”

This gracefully written and well-argued book deserves a wide readership. One hopes that readers will take to heart Marris’ chief insight about conservation: “There is no one best goal.” She bravely and correctly concludes, “We’ve forever altered the Earth, and so now we cannot abandon it to a random fate. It is our duty to manage it. Luckily, it can be a pleasant, even joyful task if we embrace it in the right spirit. Let the rambunctious gardening begin.”

Ronald Bailey is Reason magazine's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is now available from Prometheus Books.