• Biodiversity has been defined as one of nine planetary boundaries that help regulate the planet’s operating system. But humanity is crossing those boundaries, threatening life on Earth. The big question: Where precisely is the threshold of environmental change that biodiversity can withstand before it is destabilized and collapses planetwide?
  • The planetary boundary for biodiversity loss was initially measured by extinction rates, but this, as well as other measurements, have proved to be insufficient in determining a global threshold for biodiversity loss. At present, a worldwide threshold for biodiversity loss — or biosphere integrity, as it is known now — remains undetermined.
  • However, thresholds for biodiversity loss can be clearly defined at local or regional levels when an ecosystem goes through a regime shift, abruptly changing from one stable state to another, resulting in drastic changes to biodiversity in the changed ecosystem.
  • While the planetary boundary framework provides one way of understanding biodiversity or biosphere integrity loss, there are many other measures of biodiversity loss — and all point toward the fact that we are continuing to dangerously destabilize life on Earth.

Biodiversity. When you hear this word, what do you picture? Iconic animals like African elephants, gray wolves and humpback whales? Or multicolored coral species that make up a reef system? Or bacteria and microbes that regulate nutrients in the soil, or oxygen-releasing phytoplankton that live in the ocean’s sunlit zones?

While biodiversity does embrace all these living things, the concept extends beyond mere species diversity or abundance. It also encompasses the infinite variety of genes that allow animals and plants to adapt and survive, as well as the diversity of planetary ecosystems, and the different functions that organisms and ecosystems play in our intricately connected world.

In short, biodiversity is the living web of species and ecosystems that form the basis of life on Earth. Humanity, of course, is part of biodiversity, but it is also a driver of biodiversity loss. Homo sapiens can negatively impact species and ecosystems through a multitude of actions, but we are also dependent on biodiversity for food, energy, medicine, economic security, and our overall well-being.

With biodiversity embracing such a wide breadth of organisms, ecosystems and genes, it can be challenging to understand the full extent of humanity’s impact on it, especially when one considers the fact that we only know about 20% of Earth’s species. There are, however, plenty of indicators to suggest that human activities are placing exceptional pressure on biodiversity.

For instance, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) estimates that about 77% of the land and 87% of the ocean have been altered by humans, which has led to a loss of 83% of wild mammal biomass, and half of the world’s plant biomass. The IPBES also suggests that more than a million plant and animal species are currently threatened with extinction, potentially putting us on a path to what has been dubbed Earth’s sixth mass extinction.

The question bedeviling scientists: Will there come a point when humanity will have pushed biodiversity past a point of being able to recover, imperiling the very stability of Earth’s operating system and putting humanity and possibly all life as we know it at risk?

Researchers have been grappling with this question since the development of the planetary boundary framework, a theory that argues Earth has nine biophysical subsystems or processes with clear limits beyond which they cannot withstand anthropogenic pressure. If humanity stays within the “safe operating space” of these boundaries, life can thrive, the theory suggests. If the thresholds are crossed, humanity can push Earth into a new, dangerous state that isn’t as accommodating to life as we know it.

While there have been attempts to define a global threshold for the biodiversity planetary boundary, no conclusions have been drawn. One thing researchers do tend to agree upon, though, is that it is incredibly hard to measure and define biodiversity loss, particularly on a global scale. But that isn’t to say biodiversity isn’t in trouble; there are plenty of ways to see that humanity is placing extreme pressure on biodiversity, and in the process, imperiling the integrity of our world.

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