Climate change is a hot topic. Decades of data have shown that worldwide temperatures, on average, are rising and the potential for ecological devastation is a reality that places the blame squarely on our environmental negligence. This negligence continues to this day as the United States attempts to shut down its own Environmental Protection Agency out of short-sighted arrogance, and the monumental power of capitalist greed. But in order to understand the impact of climate change and what makes our post-industrial global warming so dangerous, it is important to understand the history—and prehistory—of how humans have interacted with their environment. As an apex species since the late Cenozoic, humanity has altered its environment to suit its needs, even thousands of years prior to the development of agriculture. Of course, the environment has also—disproportionately up until today—shaped humanity’s course. Nature is powerful, after all.

One of the most puzzling situations is the existence of the Sahara Desert. If you were to fly to Algeria with a trusty palaeontologist friend to visit the dried lake beds deep in the arid, rocky south—the heart of the desert—you’d be startled to see clear evidence of thriving plant and vegetable matter that had once existed there thousands of years ago. From paleontological records to the earliest artistic depictions of the humans that lived there, the consensus is that the Sahara was once a wetter and more humid place, during the “African Humid Period.” So, what happened?

Around 10,000 to 8,000 years ago, pastoralist humans first started migrating around what is today the Sahara, bringing some basic farming and domesticated livestock with them. At the same time, the Sahara began to shift towards becoming much more arid. Thus, we get to a “the chicken or the egg” situation; did the environmental shift from the African Humid Period lead to humans changing their pastoral and agrarian behaviours? Or . . . Was it perhaps humanity that had a role in changing the environment with their behaviours? When you look at how enormous the Sahara is, this sounds absolutely absurd. Sure, today we are close to destroying the planet because of industrialization on a global scale, but how could humans change such a vast swathe of land in the early Neolithic era?

Indeed, scientific orthodoxy believed the idea that humans were influenced by their environment. However, Professor David Wright of Seoul National University has recently brought about a more anthropocentric hypothesis, backed with models using prehistoric, historic, and paleontological data. While not directly implicating humanity, the data shows that humans played a majorly active role.

Current academic orthodoxy presents the desertification of the Sahara as something outside of human control. Small changes in the Earth’s orbital period influenced and weakened monsoons. With less rain, the Sahara biomass reduced, which led to the first small patches of scrubland. This in turn increased the ability for the region to essentially reflect solar radiation and sunlight brightness (it’s “albedo”), which started a feedback loop of further helping weaken monsoons and warm the region. The result accelerated, helped in small parts by humans who shifted towards pastoralism and basic agriculture around the Nile, and, as a result, the Sahara rapidly turned into a desert.

Wright claims that this hypothesis, when looked at in detail, has some internal issues and doesn’t provide strong enough arguments on how the influence of the monsoons effectively accelerated the desertification. He claims that the “patchiness” of desertification happening in different times and places, influenced by various regional micro-climactic conditions, cannot be fully causally explained by this monsoon-feedback-loop hypothesis. Instead, Wright believes that, while the external environmental effects made the Sahara ecosystems fragile, it was the influx of humans to the region which caused irreversible ecological change, moving it past a “tipping point” that led to its rapid desertification.

The idea of an ecological “tipping point” is conceptually simple, but bears universal relevance. When a number of internal and external factors combine together in certain ways, they act as stimuli for a biological ecosystem, which, in turn, reacts to these factors. However, when all of these factors are just “too much,” ecological change propagates and accelerates—kind of like rolling a ball up a hill, reaching the peak or “tipping point,” and then watching it roll down. Today, global warming puts us at a worldwide tipping point that is extreme in scale and intensity for its ability to rapidly change not just one ecosystem, but entire biomes and global biotic systems simultaneously. Traditionally though, these ecological shifts are relegated to ecosystems, and sometimes insufficient paleontological data can lead to incorrect conclusions.

Wright thus uses his collection of paleontological, prehistoric, and historic data as the basis of his explanation. He states that three criteria would need to be met for the anthropocentric hypothesis to have credence: the system must already be weakened and close to change; the system’s internal factors would not be as strong as external factors when reaching the tipping point; and human patterns of movement, pastoralism, and agrarianism must synchronize with known patterns of Sahara desertification.

There is wide consensus that the ecological mechanisms of the Sahara were weakened in some way or another, particularly because of the weakened monsoons and the feedback loop. Where Wright differs is the impact of these and their patterns of desertification. According to paleontological data, the first signs of patchy desertification started from the northern parts of the Sahara and eventually moved rapidly west and south, away from the northern Sahara and the Nile.

With a weakened Sahara, it would be easy for any external factor to act as a tipping point. Why didn’t internal environmental factors accelerate these? Wright outlines various microclimate examples of “desertification patchiness,” which imply the monsoon-feedback-loop as an “internal factor,” not being strong enough to change the Sahara so rapidly. Instead, he points to prehistoric and historic evidence of human pastoralism changing landscapes, drawing upon the earliest records of landscape manipulation up to the recent decimation of the grasslands in the Americas through settler-colonialism. Humans throughout history have had the power to alter landscape in various ways, and would serve as a sufficient external factor to change at least small, but significant, parts of the Sahara. Decisively, Wright combines this hypothesis with existing patterns of floral change in ecological models of the prehistoric Sahara, showing that external factors would be necessary to reach a “tipping point.”

What about human activity? Large-scale models have shown that sediment runoff from the Nile progressively increased around the end of the African Humid Period, which can be traced to increased farming and pastoralism. Furthermore, prehistoric floral data shows that an abundance of Saharan plants were quickly wiped out in favour of scrubland and biomass homogenization, characteristic of what humans tend to do when bringing grazing mammals and conducting small-scale farming in uninhabited land. All of this data follows the general pathway of Saharan desertification, and Wright concludes that this third criterion is also met, cementing humans as an external causative factor. Of course, humans didn’t rapidly and intentionally desert-ify the Sahara. Rather, Wright argues it was a result of an “apex species” making its own land more productive, taken to the extreme and accelerated by already existing weakened ecological conditions. Thus, Wright argues that the desertification of the Sahara was as much a natural process as other species changing their environments, with external environmental systems like the monsoons intensifying the scale of this change.

While this recent hypothesis will soon be up for further scientific debate and response, it brings us back to the fundamental impacts of climate change. Humans have changed their environments for centuries, even in non or pre-agrarian societies, but, while humans acted as potential causative agents in turning the Sahara into a desert, this was a singular—although large—collection of regional ecosystems. The reality of climate change today is that it smacks the entire planet, and is squarely within the bounds of direct human influence. We have unfortunately destroyed environments for centuries, as this hypothesis has shown us, and we are at a point where this unbridled destruction has caught up with this planet on a global scale. At this point, the effects are irreversible, and we have gone beyond numerous tipping points. The question that remains is: how can we deal with the spectres of our past, and fight against those who believe in the nihilistic destruction of the environment in our future?