Our New World

Our New World

Much of “The Natural History of the Present” looks back toward the America the Europeans found, the fragrant narcotic ‘natural world,’ even then much modified by its earlier human inhabitants, soon emptied of them by European diseases. Parts look forward to a new world where people once again let nature regain control. To look back to an ideal past is a very Western behavior: the Roman poet Hesiod looked back to a ‘golden age’ from his of iron, so did the Greeks, and the Christians (the Garden of Eden). A golden age formed one of the Hindu cycles of time. Are these memories of the hunter-gatherer life, when at certain seasons fish were there for the taking and at others fruit hung from the trees? We moderns look back to the golden days of childhood, a modern development, when in our memories, we spent long afternoons picking blackberries in the long grass. Audubon clearly saw the end of the golden age of the American wilderness coming. He regretted the loss of the great trees (he complained he never saw a ‘great tree’ in England). He built a sawmill on the banks of the Ohio to saw their trunks, then lost it in the cash squeeze of 1837. He took with his paints to the woods in the hope of other successes. He wrote admiringly of those men who were ‘civilizing’ their landscape by logging and clearing it. What other choice was there? The past is gone and the future may be less susceptible to change than we think. Like John Muir, Audubon had little connection to Native Americans, the true native ‘men of the woods.’

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Plants and animals have always been long distance travelers. Now we move them from place to place by ship and plane. New plants whose chemistries the native insects and microorganisms find unpalatable or poisonous, and so don’t eat, may (as they lack predators, competition or parasites) take over ecosystems. Then, foodless, populations of native plants, animals and invertebrates decline. Native or alien plants and animals may become invasive in ecosystems degraded by logging, settlement, altered water tables or nutrient pollution. Such changes expand habitats for some organisms and shrink them for others. Thus high water tables have let monocultures of silver maple (a native tree) replace the mixed deciduous oakwoods along the regulated middle Mississippi, with the loss of many game animals and birds. White footed mice and white tailed deer have few predators in the fragmented woodlands of the suburban northeast, greatly increase in number, eat ornamental plants and bird food, infect each other (and the local human population) with Lyme disease and prevent regeneration of the forest. Alien plants and animals may take over if they find the habitat to their liking. If they lack competitors are not eaten by insects, microbes or vertebrates (thus lack parasites and predators), their populations are not controlled, and they do become part of the local food web (for instance, by being eaten by an insect which is eaten by a bird). Such organisms include purple loosestrife, Eurasian milfoil, Japanese knotweed, European wild boar. Some of them can probably be controlled by introducing insects specific to them; by encouraging their picking for profit (say, with loosestrife); or with hunting (open season on boar). Introducing insects is risky, since the insects themselves lack local microbial and insect predators, may find other plants to their liking and their populations grow out of control. If the attempt at control works, the introduced insects become food for local birds and insects and introduce the new plants into the local food web. Introduced diseases in trees, many of them fungi (blister rust in pines, phytophora in oaks, chestnut blight, Dutch elm disease, beech decline), are essentially uncontrollable. So may be some introduced insects (perhaps wooly adelgid in Hemlocks and emerald ash borer). These introduced organisms will change the landscape, modifying forests and meadows as much as we, our grazing animals and our nutrients falling from the air. The chestnut blight of the early twentieth century perhaps changed northeastern forests the most by eliminating a common tree and a large and dependable supply of autumn carbohydrates, food for people, bears, deer, buffalo, squirrels, turkeys. Dutch elm disease changed the street profile of American cities from the tall, vase shaped American elms (100 feet high) to the fat stubby profile of Norway maples. After some hundreds of generations the insect and plants will find their populations coming under control as local insects and microbes adapt to them and they become part of the food chain. Some of the plants under attack (such as the American elm, which sets seed before being killed by the Dutch elm fungus) will develop resistance to their diseases. Elms in Europe suffered a catastrophic decline several thousand years ago but recovered. The problem is that plants, whose time between generations is years to decades, take much longer to adapt than most insects and microbes, with a generation time of weeks to minutes. The woods and meadows will adjust to the newcomers but will be different.

How to evaluate such change? In the near term, most such changes (climate shifts, new organisms, more nutrients) makes things worse. More nitrogen from the combustion of fossil fuels falling from the air tends to convert the perennial grasses of Middle Western prairies, whose roots transfer huge amounts of carbon to the soil, to annual grasses, whose carbon storage capacity is negligible. The long term is more difficult to evaluate. In the northeastern United States, Eurasian honeysuckle, distributed with autumn olive and rosa rugosa 50 years ago by state conservation departments to provide food and shelter for game birds, are now considered invasive. They are so in old fields (this was more or less the intention). Honeysuckle forms impenetrable clumps, used by as nesting and foraging sites by warblers and sparrows; their berries are eaten by migrating thrushes. Meadows are unnatural habitat in much of the northeast and the return of the forest would shade much of the honeysuckle out, though, its seeds spread by birds, honeysuckle would colonize openings in the forest left by falling trees or by logging, and so maintain itself in the ecosystem. Some insects feed on honeysuckle and butterflies nectar on it. By growing in openings, honeysuckle would compete with the native trees and herbs (early succession or sun loving species like white and yellow birch, pin cherry, oaks, the spring emphemerals of the forest floor, and the insects and other animals associated with them), that also colonize such openings and maintain the forest. Whether this is good or bad depends on how much the honeysuckle takes over and how it affects the regeneration of the forest. One could argue, for instance, that the silver maple monoculture along the Mississippi is undesirable from the point of view of a more complex ecosystem but there is little to do about it except plant oaks on higher ground as long as water tables remain artificially high. In the case of honeysuckle in the northeastern forest, some honeysuckle (not honeysuckle in every clearing) may simply add to its diversity and its variety of moths, birds and butterflies.

We have to face the question of how much we accept our new world. The survival of Pacific salmon along the northwest coast of North America is an example. Salmon numbers there have been dropping, partly from climate change, partly from dams, partly from degradation of spawning habitat in the rivers and tributary streams, partly from competition with introduced fish. On the Columbia River, introduced shad (introduced from the North American east coast) now are thought to make up most of the missing biomass of salmon, which are in serious decline. Shad were introduced in the early twentieth century and fished mainly for their roe, which was a favorite of eastern gourmands (the fish itself is also a spring delicacy in the northeast). Since the 1980s shad populations in the Columbia River have boomed. There is only so much food and space in the river and the ocean, for species that occupy similar niches: only so much fish of both can survive. Salmon populations are also affected by rising temperatures in the river and the ocean. These are likely to continue to rise, depressing salmon populations further. (Salmon will move north, into the rivers of the Arctic Ocean.) Dams don’t seem to bother shad, a more fragile fish (but one perhaps capable of more rapid reproduction than salmon, though salmon is a weedy fish, capable of rapid reproduction under favorable conditions). Dams can be modified to be more friendly to salmon and river flows adjusted, without sacrificing much of their power. Many other things can also be done for salmon. Ocean fishing, which catches salmon before they reach the river, and so prevents them from spawning, should be stopped (ocean fishing catches about 70% of some declining runs). All the hundreds of small spawning streams whose gravels have been silted in by logging and road construction should be restored by adding gravels, controlling erosion, planting trees, stream by stream. (A good work for a conservation corp of draftees.) Irrigation diversions should be screened so juvenile salmon don’t end up in cornfields, so many to the acre. The restoration of degraded river habitat may do more for restoring Columbia salmon than removing dams. (This varies from dam to dam: unnecessary dams or dams that produce little power or interfere too much with the life of salmon should undoubtedly go.) Thus we can probably have salmon and dams, within climatic limits. We will need some dams in the new solar powered world, to provide base line power and even out the variations in solar supply (the latter the worst use of dams, since the flows have little relation to natural ones, from the point of view of the fish). The Columbia is full of fish, just not those fish that were historically there. This state of affairs can be adjusted but probably not largely changed, especially considering the climatic changes we have put in motion. But improvement in the fish habitat in the river would make life better for everyone living in the river basin.