Why it matters: Most discussions about climate change and humanity’s impact on the environment focus on factors such as ice cover and global average temperatures. However, recently published research examines a broader range of factors to illustrate how civilization is moving into uncharted territory compared to the last several thousand years.
According to a recently published analysis based on numerous studies, Earth has done this crossed six of nine environmental boundaries that have maintained the conditions under which human civilization has developed. The research seeks to gain a comprehensive view of how the planet is changing in ways that modern societies have never experienced.
Climate change – the most intensely debated aspect of humanity’s ecological impact – is just one factor that is upsetting the conditions that have prevailed on Earth for about 10,000 years. Others, such as biodiversity, forest cover, freshwater availability and biogeochemical fluxes (the relationship between freshwater, ocean and soil), are also well outside the norms established during this period.
The term “Holocene” describes the relative stability of the planet’s temperature and environment since the end of the last ice age about 10,000 years ago. The entire history of complex human civilization, including agriculture and city building, took place during this period. Scientists have used nine “frontiers” to define the conditions conducive to this development, all of which have been at risk since the beginning of the Industrial Revolution.
In the diagram above, the green zones represent conditions that modern humans are accustomed to, while the red areas represent boundaries that have been exceeded. The darker red color shows which areas are most at risk. The extreme ends of the diagram are fuzzy because researchers either don’t have enough information about them or don’t know how unusual the situation can become.
The integrity of the biosphere concerns biodiversity and is the area at greatest risk. Studies suggest that human land use in the late 19th century caused the rate of species extinction to rise above normal Holocene levels, while population and food production explosions beginning in the 1960s exacerbated the problem. However, the analysis emphasizes that overpopulation is not the problem. Human civilization can theoretically support 10 billion people with appropriate adaptations while maintaining a stable environment.
One area where the potential risks of human intervention are largely unknown concerns man-made substances such as microplastics, nuclear materials and various chemicals. While there is extensive debate about the harmful effects of these substances on human health and the environment, their ability to threaten Earth’s habitability remains unclear. The long-term consequences, ecological impacts, and interactions of these man-made materials with natural systems are the subject of ongoing research and concern.
The ozone levels represent a case where humans have succeeded in reverting conditions toward Holocene norms. Since the ratification of the Montreal Protocol in 1987, ozone depletion rates have recovered and are now outside safe limits only in spring over Antarctica and southern high latitudes. Scientists say this and other factors prove it is not too late to act.