There are few fields whose findings have such a clear and wide ranging impact on every other aspect of human civilization. The rise and fall of dynasties, the great deeds of armies and generals, the wealth and poverty of nations, and the daily life of men and women across human history were molded by the ecological setting in which they occurred.
A book I often recommend to those who doubt that environmental history is essential to making sense of human civilization is Alfred Crosby’s Ecological Imperialism: The Biological Expansion of Europe, 900-1900. Over the last three decades a torrent of books and articles have been written to explain why the West was able to rise above ‘the rest’ and establish global supremacy. While of the same vein as these works, the question that animates Ecological Imperialism is slightly different: why were Europeans so successful at reproducing European society (and completely displacing the previous inhabitants) of some locales but unable to accomplish this same feat in other locations? Why were white settlers in North America, New Zealand, Australia, Argentina, and South Africa fantastically more successful than their fellow colonists in Brazil, Mozambique, Panama, or New Guinea?
The answer, says Crosby, is ecology. European expansion was not just a movement of peoples, but of entire environments. For settlers to survive and thrive they must be able to secure food, construct buildings, and move about from place to place. European civilization allowed Europeans to do this on a scale new to human history, but the successes of Western civilization cannot be separated from the environment from which they sprang. Its great cities, armies, and ships were ultimately built upon a unique suite of European flora and fauna. When transplanted far from their homeland these alien organisms do better in some lands than in others. Places where climate and local disease prove hostile to European biota, like central Africa, are places where Western imperialists could only establish an ephemeral presence. Places like Brazil or Mexico, less deadly to European life but unsuitable for large-scale colonization without adopting indigenous crops and farming techniques, produced creole cultures that mixed European and Amerindian traditions. In Australia, New Zealand, North America, and the South African coastline the only environmental constraint European settlers faced was distance. The geography, climate, and ecology of these places were perfect for European biota, allowing them to displace native life without conscious effort.
The displacement was complete and utter. American readers may be surprised to find out how much of America’s ‘natural and wild’ wilderness is made of European aliens of recent import. Sparrows, starlings, house flies, honeybees, garden snails, earthworms, common rats, white clovers, dandelions, Kentucky blue-grass, stinging nettles, knot-grass, broadleaf plantains, Bermuda grass, periwinkles, mayweed, ground ivy, knapweed, milk thistles and almost every type of grass you can find east of the Mississippi originated in Europe and came to the United States in the two centuries after 1650. And that is just a small sample of the hundreds of plants and animals that came to America along with the Europeans. What started as a few alien weeds accidentally carried across the sea grew to dominate entire ecosystems. By 1940 an ecological survey in Southern California could report that “63% of herbaceous vegetation in the grassland types, 66% in the woodland, and 54% in the chaparral” were naturalized plants.
The expansion of European biota across the land was not simply a consequence of European migration. In most cases it was an essential precursor to large-scale European immigration itself. European colonization of New Zealand’s South Island is a case in point. The first settlers in New Zealand did not believe that sheep could ever prosper there, for both islands, being carpeted by ferns or covered with dense forest, had no grass to speak of and nothing sheep could survive on. Initial attempts to remedy the situation by introducing flowering plants to New Zealand failed. The plants would grow but could not reproduce: New Zealand had no insect species adapted to pollinate them! It was not until settlers brought honeybees to the islands that the situation changed, leading to an explosion of European plants across both islands. The new grasses and clovers were perfect feed for English sheep, and it was not long before the sheep had reached such numbers that they became one of New Zealand’s chief exports and an economic pull for more migrants.