REASON, June 6, 2001
Rainbow-Colored Day Bats
Or, how human action increases biodiversity
I first imagined the idea of rainbow-colored day bats some years ago, when I was musing about why birds dominate the daytime skies and bats soar at night. Why should bats be confined to the dark hours and why should they be cloaked in dull, dun-colored fur, I wondered? Perhaps one day a scientist with an artistic soul might genetically engineer a species of colorful bats that could thrive during the day. That would be a real addition to the world's biodiversity. So far, rainbow-colored day bats remain a figment of my imagination. But the record already shows that human activities don't just threaten biodiversity, as most environmentalists would have it. No, human activities can also increase biodiversity.
Everyone knows that the force of natural selection is the generator of the millions of diverse living things in the world. What often goes unacknowledged is that artificial selection by human beings has also created novel living things. Traditionally, farmers have been the force behind a lot of biodiversity. The International Rice Genebank at the International Rice Research Institute in the Philippines contains the seeds from a total of 67,015 different varieties of rice from the Asia-Pacific region, of which 64,608 are cultivated varieties and a mere 2,407 are wild. In other words, farmers for thousands of years have been propagating the genomes of rice by selecting the varieties they prefer. The same holds true for wheat and corn: The International Center for the Improvement of Maize and Wheat stores 123,000 wheat seed samples and 17,000 corn seed samples. Thousand of the varieties were created by farmers over the centuries through plant selection.
The expression of genes in domestic animals, too, has been greatly altered by the hand of humanity--one need think only of the differences between a Great Dane and a Chihuahua. Cows range from fat, slow European Holstein milk cows to sleek hardy Brahma beef cattle that were adapted to thrive in tropical climes.
The spread of domestic farm animals is often portrayed as being ecologically harmful, but a recent book, The Ghosts of Evolution: Nonsensical Fruit, Missing Partners, and other Ecological Anachronisms (Basic Books), by Connie Barlow, points out how non-native farm animals help restore some native South and North American plant species to their original ranges. American plants with large fruits--avocados, honey locusts, pawpaws, and others--evolved to be dispersed by large, herbivorous mammals like mastodons, mammoths, American camels, and giant ground sloths. These large mammals were killed off by invading human hunters at the end of the last Ice Age and, as a consequence, the plants' natural ranges were severely reduced. Some were even perhaps heading toward extinction. However, cows and horses introduced by Europeans now act as replacements for some of the plants' missing partners; they help disperse the fruits over more of their original ranges.
Humans also can aim directly at restoring species. The American Chestnut Foundation plans to bring back the American chestnut, which was devastated by blight in the early part of the 20th century. The foundation has endowed the American chestnuts with blight resistance by crossbreeding it with Chinese chestnuts. The foundation hopes to begin restoring the new-old American chestnut to Appalachian forests in 2012.
More controversially, humanity also enriches ecosystems by moving new species into new regions of the globe. As Cornell University biologist David Pimentel points out, some 50,000 non-native species now reside in the United States. University of California at Davis evolutionary biologist Geerat Vermeij concluded in a 1991 Science article, "Invasion usually results in the enrichment of biotas [the total flora and fauna] of continents and oceans." In layman's terms, introducing species tends to raise the total number of species living in a given ecosystem, not decrease it. For example, the number of land-bird species living on Puerto Rico rose from 60 in pre-Columbian times to 97 today.
The advent of modern biotechnology gives humanity a powerful new tool to speed up artificial selection. Biotech can also protect, preserve and enhance biodiversity--even helping to prevent extinction. Last year, an international group of biologists proposed in Science magazine that a web-based network of gene banks be established to preserve the genetic material of some 5,000 threatened or endangered animal species. Tissue samples can be stored in liquid nitrogen (-70 centigrade) indefinitely and perhaps be used by biotechnologists later to clone extinct or endangered animals that could be restored to the natural world. Already, scientists are planning to clone threatened species such as gaurs, Sumatran tigers, and bongo antelopes. They may even clone extinct species like Spanish bucardo mountain goats. Larry D. Agenbroad, a professor of geology at Northern Arizona University, thinks it may even be possible to bring back the woolly mammoth by using genetic material found in mammoths buried in permafrost. The mammoth clones would be made using Asian elephants as surrogate mothers.
On a more commercial note, scientists have already used genetic engineering to increase the diversity of genetic traits found in many crop species, including pest and herbicide resistance, virus resistance, and improvements in some nutritional factors. Aqua Bounty Farms has created a genetically enhanced salmon that grow up to 600 percent faster than conventional salmon. A typical 14-month-old salmon is usually 3 to 4 inches long while Aqua Bounty's enhanced salmon can grow to 15 inches long and weigh over 6 lbs. in that time. Aqua Bounty also believes that they can similarly enhance trout, tilapia, and Arctic char by inserting into those species natural growth genes taken from Chinook salmon and another fish called pout. These genetically enhanced fish grow no bigger than conventional fish, they just grow faster.
There are no rainbow-colored day bats yet, but artist Eduardo Kac, working with French geneticists, created a genetically modified rabbit, Alba, whose fur glows with a green under black light. Alba glows green because scientists added a green fluorescence gene taken from a jellyfish to her genome when she was an embryo. Who knows? Sometime soon, an inspired artist-geneticist might create a new species of bat by adding genes for better day-time sight and genes for the fur of yellow tabby cats and glowing green rabbits. The artist-geneticist might also select genes to make the day bats usefully insectivorous so that they could clear the air of gnats, no-seeums and mosquitoes; to allay ecological worries, released day bats might be made sterile. The birth of Alba and the long history of human additions to biodiversity gives me hope that the day isn't too far away when I can look out at my back garden while drinking my morning coffee and watch a flock of day bats chirping and flitting playfully through my cherry tree.
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