How humans have changed the world
The different emigrational routes humans took out of Africa in the Late Pleistocene can still be observed through the sudden introduction of new wild and domesticated species in these areas. Nicole Boivin’s archaeological research regarding the human-environmental co-evolution cuts through the traditional divide between the natural sciences and humanities. As a director at the Max Planck Institute for the Science of Human History in Jena she focuses on the entanglement of biological, cultural and ecological processes from prehistory to the present. More recently, as part of the ERC-funded Sealinks Project, she is also investigating the emergence of long-distance trade and connectivity in the Indian Ocean, and its ecological and environmental consequences.
How has the evolution and progression of humans changed the ecosystem?
Humans have certainly altered ecosystems in very significant ways over the last 10,000 years, since the development of agriculture. Agriculture allowed for increased population sizes, and led to the domestication of crops and animals. These domesticates have spread all around the world, and represent a huge proportion of global biomass today. The spread of agriculture has led people to open up landscapes for cultivation and pasture by cutting down trees, we can see a record of deforestation in palaeoecological sequences. But it is possible that human influences go back even earlier, into the Palaeolithic period. Many researchers believe that humans had at least a partial role in the disappearance of the many large animals that once walked the earth and that are now extinct – called megafauna. The extinction of many megafauna about 50,000 years ago had many knock on effects, for instance reforestation, and some argue this has lead to global climate change.
Are there any areas or landscapes with a healthy and intact ecosystem left on this planet?
I think there are very few if any areas that have not been impacted in some way by humans, and this has probably been true for a few thousand years, at least. But I think that to call all of these human-transformed areas ‘unhealthy’ is wrong. Human alteration of landscapes does not need to be destructive, and it has not always been so. Defining a pre-set, unchanging ‘healthy’ and ‘stable’ ecosystem also does not take into account that ecosystems are subject to ongoing change through evolutionary time. Humans and their activities are some of the many things that shape the ecosystem change.
Which technological, social or cultural advances affected flora and fauna the most?
The primary driver of change has been agriculture, this is probably the most significant shift in terms of our ability as humans to transform the earth. But other key changes have included urbanization, which has led to large population centres that demand more intensive forms of agriculture. The outcome of urbanization, from the Bronze Age onwards, has been agricultural intensification, deforestation, species invasions and extinctions, and geomorphological and hydrological change. A recent publication by colleagues in Potsdam shows that the kind of irrigation-driven human activities, which led to the drying of the Aral Sea in recent decades, also already occurred almost 2000 years ago, and lead to the drying up of the Lop Nur lake in the Tarim Basin.
Another key factor of change has been globalization, which has spread a range of species well beyond their native range. Processes of proto-globalisation began several thousand years ago, and along these early trade routes, a broad range of domesticated plants and animals moved, but also invasive species that have sometimes had very destructive effects. Also moving with humans were a range of weeds, diseases and other species capable of transforming ecosystems in diverse ways.
To what extent has the ecological diversity changed because of them?
Ecological diversity has been dramatically transformed everywhere. The biggest shift, however, has been the replacement of native species with introduced domesticates. But humans have also altered ecosystems more subtly, favouring certain species over others, for example. Many ecosystems have been subtly altered for millennia, both intentionally and unintentionally, resulting in an increase in desirable species, including non-domesticated, ‘wild’ species. In other cases, human predation has decreased the size or frequency of species of use to humans, like particular molluscs or game animals that were eaten by people in the past.
Are there any recurrent recognizable patterns that have affected the ecosystem throughout the millennia?
Most processes that are happening today have been going on for a very long time – domestication, cultivation, irrigation, deforestation, extinction, erosion, pollution, landscape modification, alteration of hydrological systems and lakes, etc. These have ancient origins. Today they are more frequent, and often occurring on a larger scale. And new types of processes and materials have been introduced – fossil fuels, plastic, and nuclear energy for example.
What can we learn from the history of the ecosystems for the development of a sustainable economy?
For me as an archaeologist, a clear take-away message is that humans are capable of creating or contributing to the creation of both degraded ecosystems, and resilient ones. The archaeological record contains examples of societies that have altered environments in different ways, and shows us the outcome, both for ecosystems and the societies dependent on them. Humans have great creative abilities, and the potential to learn from both the past and their mistakes. We can look to the success stories of the past to learn how to do things better. We can look at the failures to see what not to do. But what we must do is take responsibility for our actions. We have been altering the earth for millennia – that much is very clear. We have a responsibility not only towards ourselves but to all species on earth, to accept that altering ecosystems is something we do, and to steer our societies and activities in a sensible way. Ecosystem transformation is unavoidable with the size of the population of humans inhabiting the earth today. We can’t change this, but thinking long-term we can change how we alter environments, and devise policies that ensure that ecosystems will continue to support human societies as well as the many other species we share the planet with.
Interview: Judith Reichel