43 pages • 1 hour read
Alfred W. CrosbyEcological Imperialism: The Biological Expansion of Europe, 900-1900
Nonfiction | Book | Adult | Published in 1986A modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.
Chapters 7-9Chapter Summaries & Analyses
Chapter 7 Summary & Analysis: “Weeds”
When European colonizers brought crops and animals to their new settlements, they carried with them a diverse segment of the European flora in the form of both crops and weeds. According to Crosby the weeds may have been even more important than the intentionally transported species in transforming much of the world into European adjacent ecosystems.
To define why weeds were so important in ecologically colonizing the globe, the text first defines exactly what it means by a weed. Weeds are not necessarily undesirable; many “weed” plants have been considered important cultivars in certain areas. Weeds are defined by their hardiness and their rapid reproduction rates, and for these reasons they were perfectly suited to the recently invaded lands in the New World. European expansion necessitated the establishment of European infrastructure and agriculture across the globe. To achieve this, the European settlers had to remove huge swathes of native plants, tilling the soil and planting European species in their place, building roads and cities, and otherwise ravaging the landscape. This disturbed land was the perfect place for certain plants that thrive in harsh conditions to flourish. European plants like plantain and stinging nettle, weeds that now live worldwide, grow best in disturbed soil and are able to survive trampling and other interference by humans and livestock. They expanded rapidly in the New World and began to outcompete native species in many areas, like the South American pampa where gigantic prairies of native grasses were eaten by European cattle then replaced by less vulnerable European weeds. This issue was particularly apparent in places like Australia, where native plants had evolved apart from those on other land masses for many years and were not prepared for the influx of new competition.
In many locations, such as the American South, these weeds arrived with the first explorers and spread so aggressively that even early settlers believed them to be native, and Indigenous people cultivated them. This was the case with peach trees, which were likely introduced into Florida by 16th century Spanish and French explorers. By the time the English arrived in the South, peach trees were not only everywhere, but they were also adeptly used by the native populations for many local dishes. By the 1600s, many other European species had joined the peach in becoming synonymous with American locations, species like Kentucky bluegrass and Florida oranges.
Crosby explains that weeds, although considered a nuisance by individual farmers, ultimately helped the European colonial settlements gain long term success. The quick growth of weedy species across the land destroyed by European invasion allowed the soil to become healthier and lessened erosion, two important factors in the ultimate long-term stability of European crops and settlements.
Crosby does not focus heavily on the specifics of European crop production in the New World beyond identifying European crops as both more diverse and more efficiently farmed than those in the New World. Archaeological evidence suggests that this is not necessarily the case. Increasingly, scientific archaeological analysis has identified highly skilled food production among New World residents, particularly in South America. This stands to reason since maize and potatoes, both staples of the globalized modern food industry, originated in the Americas and were successfully domesticated there long before Europeans took up residence. Evidence has been found of advanced farming techniques in North America as well, albeit at a smaller scale than in the Old Word.
The text also points out that while European species took up residence in almost every part of the world, New World species of plants and animals very rarely invaded Europe. The few exceptions to this, such as the North American grey squirrel in the British Isles, were aided by existing issues. The European red squirrels were first thinned out by disease before giving way to grey squirrels, who had the benefit of fitness combined with decreasing competition.
Crosby does not expand on the reasons for this discrepancy beyond suggesting that it was simply due to the lack of human migration from the New World to the Old World. Yet the text makes it clear that New World grown crops were imported to Europe in huge numbers. When viewing the weeds that currently exist in places like North America, it is clear that many of them are European in origin. Yet many are also native plants. Undoubtedly a number of New World species were transported to Europe with crop imports, but few were able to thrive there. The exact reasons for this have never been identified, but it suggests that there are more complicated factors at play than those outlined in this book.
Chapter 8 Summary and Analysis: “Animals”
Like plants, a variety of animals were transported across the world both intentionally and unintentionally by Europeans. Although plant cultivation was a worldwide phenomenon by the time of rapid European expansion, Crosby states that few animals had been domesticated anywhere outside of Eurasia, and nowhere to the extent that that had been in that area. The ability to transport and introduce cattle, sheep, pigs, and other livestock became a crucial component of the success of Europeans over Indigenous populations all over the world.
Pigs were particularly destructive everywhere they were introduced. Pigs will eat almost anything and need relatively little food compared to cattle or other large ungulates. This made them invaluable to Europeans setting out for unfamiliar land; they can survive almost anywhere as long as there is water and shade. This also meant that any escaped pigs (there were many, due to their rapid reproduction rate when well fed) were easily able to survive in the wild, causing an explosion of feral swine in many areas of the world that continues to this day. Pigs and sheep were often used by early explorers to “seed” islands like the Azores with meat for harvest during future expeditions.
Horses, sheep, and cattle were also unknown outside Eurasia before the 15th century. Both were transported in great numbers all across the world and found huge expanses of grass and other native plants to voraciously mow down. In the 1700s, Spanish settlers in California introduced horses to the American West, and by the time of the Gold Rush there were so many wild horses in California that livestock owners “drove the horses off the cliffs at Santa Barbara by the thousands” (183) to preserve the grasslands for their cattle and sheep. Horses found similar success in Australia, where by 1804 up to 5,000 wild brumbies thrived in the remote back country. Cattle were also introduced in droves in the Americas and Australia and, like horses and pigs, became feral in great numbers. Other, smaller domestic animals like rabbits and even bees were first introduced in many parts of the New World by Europeans. Rabbits were especially destructive on islands, where they reproduced quickly and ravenously consumed native plants.
Unintentional animal transports also took hold across the world as international shipping became more common. Ships carried rats in their holds along with the stores of food products, and these rats exited in port cities and took up residence across nearly every continent. They became such an issue in places like Jamestown, Virginia that they almost caused the colony to fail. Rats flourish in human inhabited areas and will devour entire gardens and food stores with ease. The human effort to eradicate rats began almost as soon as rats appeared in any given area, and to this day that effort has not succeeded anywhere.
Crosby describes animal domestication as a clear advantage of Europeans over New World cultures, even more so than that of plants. In the case of animals, this suggestion is supported well by current archaeological evidence. Only one New World domestic animal (the turkey) and a handful of New World invasive species have definitively been introduced worldwide. There is some evidence that North American wild goats and/or sheep (very difficult to distinguish from each other in the archaeological record) were domesticated by early Indigenous groups but never to the extent of their parallels in Eurasia.
Although it is clear that European and Middle Eastern populations were at the forefront of bringing animals under their control, it is not necessarily clear that the animals were actually domesticated as opposed to tamed to the extent that humans could interact with and use them. Like in the case of plants, the strictly agricultural animals had much less of an impact on the overall ecology of the New World than that of the vast herds of feral horses, cattle, pigs, sheep, etc. Crosby points out that feral domestic livestock played an enormous role in destroying New World ecosystems. They also destroyed the Europeans’ crops to a much greater extent than any native pests. Although the reality of the modern world shows that European agricultural and animal husbandry efforts abroad were extremely successful, the practice brought its own problems along with it and created new problems that did not exist to the same extent in Europe. This is not to say that ecological advantages were unimportant for the development of European colonialism, but the reality of those advantages may not be as clear as Crosby suggests.
Chapter 9 Summary & Analysis: “Ills”
Disease transmission is likely the most widely studied contributing ecological factor within European colonialism. Despite this, the exact nature of how diseases spread and what diseases existed where and at what time remains somewhat unclear. The history of particular diseases has only been understood for as long as disease itself has been understood scientifically, so painting a scientifically accurate picture of how colonial diseases were so effective at killing Indigenous populations is a difficult task. Crosby makes some attempt to assign real diseases to the various plagues and maladies referred to in contemporary accounts of life in colonial settlements but ultimately concludes that no matter the disease, the simple fact that New World populations lived in relatively small, isolated populations meant that they did not have immunity to as many types of illnesses as people from highly populated cities in Europe. The book cites several modern examples of epidemics among isolated human groups as evidence that “when isolation ceases, decimation begins” (197). Several “uncontacted” Indigenous groups in the Amazon basin and the American Arctic were killed in large numbers as recently as the 1960s. Although modern medicine was not available to all these groups, even those with access to it were killed in larger numbers that populations with natural exposure to diseases like mumps and influenza. From this evidence, it can be assumed that in a time with no modern medicine and not even the slightest hint of natural immunity, Indigenous populations in Australasia and the Americas were affected disastrously by illnesses that were common in Europe.
The isolated nature of many New World natives was dangerous not only because it rendered them vulnerable to diseases they had never been exposed to, but also the low populations and lack of cultural transfer meant that the locals themselves had few diseases to pass on to the invaders. In many parts of Asia and Africa, European colonialism was limited greatly by diseases that thrive in the tropics and in dense populations. Meanwhile the Americas, Australia, and New Zealand were relatively healthy, and outside of the tropics Europeans had few plagues to worry about. The reasons for this, according to Crosby, is a combination of luck and low population. Even if a disease took hold in one population group, that group making contact with another group and spreading the illness further was unlikely. The low population is almost certainly an important factor, but Crosby does not discuss why disease was not a particular concern in the few high-density areas that did exist.
The book does touch on the early colonial and pre-colonial history of the United States, referencing the mound building cultures of what is now the Midwest as well as descriptions of 16th century social stratification in Florida. Both of these examples show that dense populations did exist at various points in pre-colonial America, and trade between many groups was probably common at various points. Many of the temples and other cultural constructs of the Indigenous populations were relatively ephemeral, built of dirt rather than stone. Archaeological evidence shows that sometime after the arrival of the first Europeans, Indigenous American populations declined rapidly, taking their cultural infrastructure with them. The only possible explanation for this is rampant disease among the population. Whatever disease or group of diseases caused this decline, it spread rapidly and extensively throughout North America. Thus, a microscopic, probably unintentional, introduction to a few areas of North America from early European explorers probably did more damage in a few years than the colonists themselves could do in decades. Before Europeans even began to travel to North America in large numbers, biology primed the land for what the invaders saw as a divinely inspired takeover by the superior culture.
Disease transmission did not only flow from Europeans to Indigenous populations in the New World itself. The West Indians brought to Spain as slaves during Columbus’s second voyage almost all died soon after arrival in Europe, and the reason given was that “the land did not suit them” (198). Like this passage, many of the first-hand colonial accounts of disease among native populations is very vague or treats the disease as a supernatural event; God wanted Europe to rule the world, so He sent a plague on the natives standing in their way. Crosby does not go into detail about how diseases were spread, but intentionality of spread may be nearly as important as the virulence of European diseases. No evidence of biological warfare used by New World Indigenous people exists while many instances have been identified in which European invaders intentionally spread disease to locals with the knowledge that it would kill them. Microorganisms put up a strong fight to take hold across the world, but they would not have been as successful without intentional help from colonists.
