Our planet’s terrestrial and marine ecosystems, together with their climatic envelopes and geological substrates, and the processes and products resulting from their functioning represent humanity’s life-support systems. Their roles include the capture of carbon dioxide and release of oxygen, supplying food, provisioning of drinkable water, controlling soil erosion, suppressing pest, recycling wastes and providing inspiration through watching and learning from nature. And these services are, in a very real sense, the result of about 3.5 billion years of relentless organic evolution, overwhelming the occurrence of five major pulses of biological extinction that occurred over the last 600 million years. Remarkably, never in the history of life has the planet “seen” more biological diversity. Ironically, within today’s pinnacle of biodiversity, since the industrial revolution but most notably in the last few decades, humanity has become a major force of environmental change, and the major threat to the life forms and life-support systems upon which everyone depends.
Recently, an international group of scientists who study the interaction of humanity with the rest of the biosphere released a consensus document in which they explicate our understanding of the current and projected magnitude of key human impacts on the planet and conclude that the evidence that humanity is seriously damaging its life-support systems is overwhelming. They point out that humanity is causing: the strongest and fastest climatic disruption since humans became a species; a massive deterioration of terrestrial and marine ecosystems; record and increasing levels of toxic pollution; massive biological extinctions, currently orders of magnitude times higher than in the distant past.
They also point to the unprecedented growth of the human population, doubling since 1970 to over 7 billion people (projected to reach 9.5 billion in 2050) with very unequal patterns of resource consumption (excessive and wasteful in some countries and social sectors). What is distinctive about this new synthesis is the elaboration that, in addition to the individual impacts listed, these factors interact in complex ways often reinforcing each other.
The scientists argue that while these anthropogenic impacts have profound consequences when analyzed separately, it is their combined assault that puts the life-support systems of humanity on the verge of reaching a tipping point — an abrupt and (for all practical purposes) permanent shift in biodiversity, ecological structure and ecosystem functioning that would imperil all societies. We now know that when multiple global pressures combine, ecosystem changes occur more unexpectedly, faster and more intensely than what would be predicted from considering each pressure separately.
Tipping points have been documented at a variety of temporal and spatial scales. This is the case, for example, of the shift of many forested areas of Latin America to savannah-like ecosystems following the combined and thus disproportionate effects of massive deforestation, burning, introduction of cattle and hunting of wildlife that followed the arrival of the conquistadores. These savannahs persist, even though they have been long abandoned for human use. Indeed, some local people, unaware of this history of human impact, regard the savannahs as “the natural ecosystem” of those localities. The fact that life “recuperated” afterward, although some of those tipping points in the distant past have been of profound and global impact, is of no consolation from the perspective of today’s global and interdependent civilization. Consider the case of the massive extinction of 250 million years ago, when global changes brought about the demise of the majority of species. Granted that post-extinction, the flora and fauna was able to “recuperate,” it took tens of millions of years for many of the different types of organisms to reach comparable levels of diversity and for life-support systems to reach a new relatively stable ecological state.
There is no way civilization could wait even 10 years for nature’s services to be restored. The consensus conclusion that the interactive effects of the five impacts greatly accelerates the chances of crossing critical thresholds leading to irreversible change within a few decades is therefore critical, as such synergistic effects would surely lead to social strife.
The scientists conclude that as a result of this destructive nexus, humanity’s quality of life will suffer substantial degradation by the year 2050 if action is not undertaken to change the path civilization is following. Given these circumstances, it is essential that, beyond scientists, society at large — the general public and government at all level — become aware of this understanding and use it to develop a reasoned recognition of the urgency of the human predicament. It is essential that policymakers commit the necessary resources and drive human action toward implementing solutions. As the consensus indicates, scientific knowledge and technological capacity are not the limiting factors now; rather, it is more a matter of human attitude and societal definition of priorities. What is needed is systematic education and communication, explaining that human well-being absolutely depends on environmental life-support systems and emphasizing the pressing need to change the ways those systems are being abused. But all is not bleak. The consensus argues that, if we start taking appropriate actions now, our trajectory can be altered — and our children will be safer and proud of us.
*The statement is available to download and sign at http://mahb.stanford.edu/endorse-the-message-to-world-leaders/
Rodolfo Dirzo is the Bing Professor in Environmental Science at Stanford.
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