Natural History

Environmental impacts of prehistoric humans

Prehistoric cultures significantly transformed their environments by deforestation, fire, construction of structures and irrigation systems, and hunting practices. These behaviors were common in many habitats where humans lived, and culminated in the start of the Anthropocene era – the epoch defined by major human impacts on the Earth. As used here, the term "prehistoric cultures" represents all aboriginal, ancestral, or Indigenous cultures that were the original inhabitants of a region prior to the local adoption of a writing system; and also includes Pre-Columbian cultures in the Americas, regardless of writing system usage. Prehistoric hunter-gatherers used fire to clear dense vegetation, improve mobility, and facilitate hunting. The development of agriculture accelerated the impact of humans on the surrounding landscapes. Farming often required clearing cropland, preparing soils, diverting or controlling water, and cultivating particular plant species. Forests and grasslands were converted into fields and pastures, while domesticated animals altered grazing patterns. Irrigation systems changed rivers, wetlands, and soil chemistry. Prehistoric and Indigenous cultures were responsible for contributing to the extinction of scores of animal species during the Late Quaternary extinction events. In that time, the majority of the world’s megafauna – large animals – went extinct. Humans caused some of those extinctions by a combination of over-hunting and destruction of the animal's natural habitat. The extinctions occurred on all continents (except Antarctica) as humans moved into new regions. Because large animals typically had long gestation periods and low reproductive rates, even small hunting pressures could lead to a population collapse. Evidence for humans as a cause of some of the extinctions includes a strong temporal correlation between the arrival of humans and the subsequent rapid disappearance of megafauna, coupled with the lack of evidence of sudden climate changes at the same time. The elimination of megafauna and the modification of landscapes had cascading effects on prehistoric ecosystems. Large herbivores maintained the environment by grazing, browsing, and trampling open spaces. By 12,000 years ago, more than 90% of Earth's tropical forests and 95% of its temperate forests were inhabited and shaped by Indigenous peoples.

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See also

• ▸Biodiversity of Colombia
• ▸Daniel Lorenzetti
• ▸Castle Rock Lake

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