Maldivian capital

“‘Pristine’ landscapes simply do not exist and, in most cases, have not existed for millennia,” – that’s the conclusion of a new study, published this week in the Proceedings of the National Academy of Sciences (PNAS).

A team of researchers, led by Nicole Boivin of the University of Oxford, conducted a comprehensive review of decades-worth of archaeological, paleocological and genetic research and found that the impact of human activity has led to widespread changes to species abundance, composition, community structure, richness and genetic diversity for thousands of years.

“The assertion that preindustrial societies had only local and transitory environmental impacts is mistaken and reflects lack of familiarity with a growing body of archaeological data,” they wrote.

All of Earth’s major continents and islands, including Antarctica, have been influenced by repeated human activity.

The authors referenced four major phases when humans re-shaped the world around them: the Late Pleistocene near-global dispersal of H. sapiens; the emergence and spread of agriculture beginning in the Early Holocene; the colonization of the world’s islands; and the pre-modern expansion of urbanization and trade beginning in the Bronze Age.

“We highlight the role of new classes of data, such as ancient DNA (aDNA), stable isotopes and microfossils, as well as new approaches, including powerful morphometric, chronometric, computational and statistical methods, for understanding changes to species distributions at various scales,” explained the authors.

The data links the expansion of H. sapiens during the Pleistocene to transformations of plant community composition and fire regime change. Pollen and microcharcoal records show that early colonists of New Guinea deliberately burned tropical rainforests to spark growth of what they considered more useful plants – a reoccurring theme throughout human history. The study argues that some plant and animal species that are abundant today are thriving because they proved to be the most desirable for humans.

Between 50,000 and 100,000 years ago, the expansion and increase of human populations has been linked with a variety of species extinctions, including the drastic reduction of “megafauna” or big beast species.

“Megafauna were keystone species whose disappearance had dramatic effects on ecosystem structure, fire regimes, seed dispersal, land surface albedo and nutrient availability,” noted the authors.

The introduction of agriculture, which is the second time frame referenced in the study, caused the creation of new domesticated species of crops and animals. Land was cultivated to accommodate favorable species, while other plants and animals suffered from the clearing of forested land. This type of land use contributed to a change in greenhouse gas composition in the atmosphere between 4,000 and 1,000 years ago.

Technological advances enabled humans to reach and colonize remote oceanic islands, which is the third phase of the study. It was so common to bring domesticated animals, crops and other species to new islands that archaeologists refer to these locations as “transported landscapes.” Transplanting new species made the islands more habitable for humans, but also re-shaped the composition and abundance of the native species.

“Polynesians introduced at least 40 plant species, mostly trees, shrubs and herbaceous cultigens. They burned and cleared indigenous rainforests, altering the abundance and distribution of species to favor useful native plants,” explained the authors.

Species of weeds, rats, insects and lizards were also unintentially brought to these new landscapes. Recent studies have shown this series of events are connected to the extinction of many birds in the Pacific islands, four genera of giant sloths in the Caribbean and nine taxa of snakes, lizards, bats, birds and rodents on Antigua between 2350 and 550 BCE.

The boost in food production to sustain growing populations paved the way for the emergence of urbanization and global trade networks–the fourth and final phase reviewed in the study. The introduction of crops like olives, grapes and figs led to the cultivation of indigenous forests. One study highlighted in the paper found that 80 to 85 percent of the areas suited to agriculture were cultivated in the Near East 3,000 years ago. Another estimate states that at least 50 new plant foods, mainly fruits herbs and vegetables, were introduced to Britons just in the Roman period.

So what is the main message behind all of this data?

The study reiterates that humans have made long-term, signifcant and sometimes irreversible impacts on the environment since our ancestors began exploring new regions of the world, and human activity has only increased into modern day. But, according to Boivin, the study also emphasizes the need to re-evaluate some approaches to conservation efforts.  

“These findings suggest that we need to move away from a conservation paradigm of protecting the earth from change to a design paradigm of positively and proactively shaping the types of changes that are taking place,” said Boivin. “This sounds scary, and it sounds very self-serving. But the reality is that there are 7 billion people living on an already heavily altered planet. It is a pipe dream to think that we can go back to some sort of pristine past.”

“The reshaping of global biodiversity is one of the most significant impacts humans have had on Earth’s ecosystems. As our planet experiences its sixth ‘mass extinction event,’ the effect of anthropogenic landscape modification, habitat fragmentation, overexploitation and species invasions could not be more apparent,” conclude the authors.