kw: book reviews, nonfiction, nature, biodiversity, invasive species
I lived on Lake Erie through most of the 1960's. During my high school years I worked at Cedar Point in the summertime. When we moved to Ohio I recall being told that the "sewage treatment system" for Cleveland was a series of pipes five miles long that took raw sewage out into Lake Erie. We took a boat tour on the Cuyahoga River to see all the bridges and buildings and how cargo vessels had to negotiate turn after turn to get to the docks. It seems they were continually spilling bilge and oil as they did so. The oil and sludge on top of the river was about four inches thick. We learned after we moved away that the river caught fire in 1969.
Lake Erie was effectively dead in those years. Oh, there were a few kinds of fish that could tolerate the pollution, mostly carp and other kinds that weren't worth catching to eat. We were warned not to swim when there was a north wind: sewage would blow ashore. The water was gray, and if you put your hand more than half a foot down you couldn't see it. One of my teachers liked to SCUBA dive in a "deeper" part of the western lake: the western quarter of Lake Erie is usually only six feet deep (less than 2m), but in a few areas it gets 20-30 feet deep, yet there are "reefs", or shallow spots that come near the surface, but they aren't visible in the murky water. In class one day he told us of being "down there" and hearing a loud crunch. He ascended and found that a yacht had run aground on a reef. He helped the old fellow get loose. The next day's newspaper had a little notice that the president of the Rocky River Yacht Club had been helped by a local teacher after "his yacht struck a submerged object." He laughed and told us, "That submerged object was the bottom of the lake!"
Fast forward twenty years. In 1988 a few specimens of a little freshwater clam from Russia called a Zebra Mussel were found in Lake Erie. Soon they were everywhere, covering the bottom, clogging drains and other equipment, and basically wreaking havoc. The little ZM's were also accused of driving the native species of lake shellfish and algae and some finfish nearly to extinction. Actually, looking back, it is clear that those declining natives were on the way out and would have succumbed before the mid-1990's, but something happened to the lake first. Zebra Mussels, as all mussels and clams, are filter feeders. ZM's happen to tolerate pollution better than almost any other freshwater bivalve. In their quest for plankton (tiny water creatures like amoebas and diatoms), each animal filters a quart of water daily. It takes out not only the plankton but many organic pollution particles also (like raw sewage - yum!). Multiply by a few tens of billions: the whole lake was getting filtered through the ZM's every week or two.
In a few years the water was noticeably clearer. The last time I saw the lake, you could see to the bottom in six feet of water, and I was told visibility is 20 feet or more in most of the lake. Cleaner water meant the native clams and mussels got healthier and staged a comeback, including those thought to be extinct. More algae now grow there because light penetrates farther. The nearly extinct lake sturgeon is rebounding. Sturgeons eat mussels, and seem to relish the ZM's. So do a few other kinds of fish such as smallmouth bass. Lake Erie is alive again. All due to a "dangerous invasive alien" that had the entire environmental movement in a tizzy for decades.
The new book by journalist Fred Pearce, The New Wild: Why Invasive Species Will Be Nature's Salvation, is full of such stories. I cribbed a few of the details above from his account, which is based on the published record. He also writes of the Guanacaste trees, the national tree of Costa Rica, which was on the verge of extinction. Its seeds need to pass through the gut of a large mammal and be partially digested to germinate, but all large mammals had been extirpated—by humans—and the trees only existed because humans had been planting the seeds. Some would grow if their shell rotted enough after planting. Seeds left lying on the ground just piled up like so many rocks. An ecologist puzzling over what to do suggested introducing horses to the area, and it worked. That fellow saved a beloved tree from extinction, but paradoxically earned himself the hatred of multitudes of doctrinaire "environmentalists.
Pearce writes of the forests of Puerto Rico, restoring themselves on land that was abandoned after plantations of sugar (and other crops) went bust. But they are not restoring themselves with the tree species that grew there before; those cannot tolerate soil changed by a few centuries of plantation cultivation. No, "alien"tree species that had been introduced or otherwise appeared in Puerto Rico over the generations, and were growing here and there, spread quickly over the disturbed land and created a new kind of forest. Later some native species were able to return also. To an untrained eye, it looks the same as the fragments of "original" forest elsewhere on the island.
To be fair, Pearce also tells of places that have suffered after certain alien species arrived. Seafarers that arrive anywhere seem always to have rats along. Some rats grasp the opportunity to go ashore. On occasion, havoc results, and they eat everything in sight, including the eggs and young of many native species. There have indeed been extinctions of endemic species on some islands and other restricted areas. Colonial America is a prime example, and one species that was nearly extincted in Virginia was the colonists, after the rats they had inadvertently allowed ashore ate through their grain stores!
Whether carried by humans or not, species have a way of getting around. As described by Alan de Queiroz in The Monkey's Journey (reviewed here), long-distance dispersal by all kinds of unlikely species happens over and over again. Of course, things that fly or float travel better than more sedentary critters, but one need look no farther than Hawaii for an example: the archipelago has many endemic species of both plant and animal, species that evolved there, and it has never been in contact with a continent, nor even closer than a couple of thousand miles. All the endemics of Hawaii are descended from animals and plants that traveled, or were taken, long distances.
Think about this: Every time a new species arrived in Hawaii and began to reproduce there, it was an "invasive alien" species. By the time the Polynesians, now Hawaiians, had been there a few dozen generations, and the first Europeans arrived, what looked like primeval forest to the Europeans was about half consisting of species the Polynesians brought with them. Since then, more and more aliens have arrived. Some, such as the giant African tree snail, are doing damage. Most have just found a way to fit into the existing ecology, have done little or no harm, and have actually enriched Hawaiian biodiversity.
This introduces a major theme of The New Wild. "Alien" does not mean "Evil". It all depends. Even seemingly evil aliens, such as the Zebra Mussel, can do good in the end. ZM's are now part of the ecology of the Great Lakes whether we like it or not. To eradicate them now would cost a great deal more than it would have cost us, by purely technological means, to clean up Lake Erie, and we couldn't even afford that! The "evil invaders" cleaned it up, but not quite for free: industries do have the cost of cleaning mussel shells off their water intake pipes and other submerged equipment.
There's a nature center we visit from time to time. On a guided tour the ranger moaned about their problems with Multiflora Roses. I guess they were originally transplanted there to start briar patches where there had been none. As it happens, Multiflora can tolerate the pollution and drought associated with the way the land had been left before the nature center was set up. Native roses from the area cannot. But now, Multiflora is considered an "invasive alien" and they are trying to root out all the rose bushes. They can't do it. It is a Hydra problem (harking to the Hydra of Hercules). If you dig out a rose bush, you leave disturbed soil behind, and Multiflora just love disturbed soil. Rose hips or fragments of root left behind typically engender several new bushes where there had been only one. One step forward, four steps back!
So what is the New Wild? It is best understood by contrast to the Old Wild, a world of wild places untouched by humans. Old-growth forests. Pristine landscapes. Primeval territories that actually have not existed for tens of thousands of years. The Old Wild exists only in our imaginations. The New Wild is a new understanding of how nature works on lands that vary from little-managed to extensively-managed to wholly cultivated, in all of which nature does what nature always does.
"Nature" is a mythical embodiment of the myriad environments and their living denizens. We think of the "forest primeval", such as the deep woods of Maine referred to by Longfellow in Evangeline, as a virgin product of nature. Humans have been in Maine, as they have been throughout the Americas, for at least 13,000 years. The Maine forests in the 1400's may have been less heavily managed than the maize-farming areas along the Delaware River, but managed they were, for the rather modest timber needs of the Penobscot people. Without people, what would the forest have been like? There is no way to know.
We do know that the forests of the northern 2/3 of North America, even those that have been little used by Euro-Americans since 1492, are substantially different now than before, because of a much-beloved (by most) group of alien species: earthworms. The silent-treading natives of legend and lore had something going for them that is seldom found now, a thick layer of moldering leaves on the forest floor. Wherever there is water enough for fallen leaves to remain a bit moist, they are soon consumed by earthworms. But this was not so from about 15,000 years ago until the 1600's when Europeans brought European earthworms ashore. This was usually not deliberate; worms came in the soil around the roots of plants brought by the colonists. Native North American earthworm species are found only in the southern half of the U.S. and further south; the northern half of the country was scraped clean of its entire biosphere by glaciers, and the native worms travel too slowly to have re-colonized the north in only 10,000 years. Earthworms are one of the most successful groups of invasive alien species. We are better off for them.
A second theme of the book is that current environmental dogma, that it is best to root out and exterminate all alien invaders, is usually wrong-headed. He gives numerous examples that show how "invasions" usually increase overall biodiversity of the invaded landscape; how the supposed extinctions the aliens are accused of causing were usually already accomplished by the time of the invasion; and how the ZM is but one example of a much-feared alien species that turned out to be a blessing in disguise and actually contributed to the overall health of the environment.
There is one metaphor that Charles Darwin used, which we must do away with: Nature as 10,000 tightly-hammered wedges. He wrote of inter-species competition as the removal of one wedge so a different one could fit in. This is not so. Take careful note: THIS IS NOT SO. Rather than many wedges tightly filling all space, think of Nature as a field with many plants growing, yet not all the ground is covered (even in a well-fertilized lawn you can see dirt between the blades). Perhaps there are 100 species of plants in this field. Cast in some seeds of another 100 species and wait a year. Then count the species growing there. Not all of the new seeds will have done well, and you may find only 75 of the 100 new species has taken root. And the original 100? You may not find every one of the original 100 species, but chances are, they are all there if you examine all the field carefully.
I recall taking a young man from Beijing on a field trip in 1984. It was only in 1980 that Chinese students were first permitted to study in American universities, so he was one of the early ones. He was a real city boy. We drove from Rapid City, SD to Billings, MT, the northern way, along US 212 through Custer National Forest (it ought to be named for Crazy Horse, IMHO) and two Indian Reservations. He saw cattle for the first time (beeves are also a hugely successful invasive species in America). Later he saw pronghorn antelopes among the cattle. I told him what they were, and he asked, "Don't they fight?" I replied that there was grass enough for both, plus the pronghorn would eat cacti and many kinds of wildflowers that beef cattle prefer not to eat. So although a state like Wyoming or Montana might have more beeves than humans, the native ungulates have not been driven to extinction. Had we passed through the national forest at dusk, we'd probably have also seen deer.
A few of the examples in the book have numbers, and they show how the usual result of multiple invasions is for species diversity to increase by 50% to 100%, both of plants and animals. An "ecology" is not a finely-tuned instrument, nor a finite collection of tightly-packed wedges, but a more fluid situation. Adding dozens or even hundreds of new species is unlikely (except on a few very small islands) to result in the extinction of any endemic species, and the new species fit in, forming a new assemblage that works as well, or often better, than before. Nature is not static. Left entirely alone, things change continually, and new species arrive while existing ones die away, from any particular patch of ground. Change is the only constant!
I've rattled on long enough. The New Wild is not quite a call to arms on behalf of a new understanding of the environment, but it is intended to open eyes to a new way of seeing nature. It is unlikely to change the minds of the old guard with their idée fixe of exterminating all alien species. It represents a growing understanding, which I hope will prevail quickly (and more quickly as that old guard retires and passes on). People tend to jump to conclusions. Influential people jump just as quickly as everyone else, which makes them dangerous. Remember the adage, "Haste makes waste." I add to it, "A sense of urgency is the Devil's tool." Y'gotta think things through. Fred Pearce has given us a book full of reasons for thinking through our environmental premises.