Planetary Boundaries: The wealth of the biosphere
Biodiversity and intact ecosystems are important stabilizing factors for the entire Earth system. However, human intervention in natural systems is threatening this ecological stability. Global diversity loss has accelerated such that we have already crossed this planetary boundary. The size of populations, as well as the number of organisms and their distribution, are also important for assessing future risks – but more data is still required.
The biosphere encompasses all the spaces on Earth in which there is life. In conjunction with climate change and the introduction of novel substances including chemicals and plastics, the stability of the biosphere is considered one of the Earth system’s three main boundaries. Crossing these boundaries poses major risks to the future of humanity.
In 2015, scientists estimated the extent of the stress which we humans placed on the biosphere. They differentiated between two aspects: the genetic and functional diversity of life. As early as 2015, the former was considered compromised. A global report from 2019 showed that almost all trends related to the latter are negative as well.
Genetic biodiversity is important because the diversity of different genetic information ensures that the sum of life is able to adapt to changes in the environment and the Earth system. The second issue when estimating the risks is the extent to which the biosphere is able to fulfill functions that are important for us and the Earth system: the “ecosystem services.”
Scientists are still working to determine whether or not the current changes have already crossed the planetary boundaries. In the case of genetic diversity, one thing is already clear: As a result of the high rate of global diversity loss, we have already left the safe operating space.
One in every eight species faces the threat of extinction
There are an estimated eight million species on the planet, from the better-known and often larger ones like vascular plants, mammals, birds, reptiles, and fish to the very small and frequently unknown ones such as insects and microorganisms like protists, fungi, and many algae. However, some microorganisms such as bacteria and archaea (prokaryotes) are not included in the statistic. Of these eight million, around one million species face the threat of extinction, according to an estimate by the experts of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES).
However, the extinction of entire species is only the tip of the iceberg when it comes to genetic biodiversity. Phylogenetic species variability (PSV) would be the preferable metric. It summarizes the degree to which species in an ecosystem are genetically related. Since data on PSV are not available on a global scale, global diversity loss is used instead – and compared to the past.
The annual extinction rate is now up to 100 times higher than it was on average in the past 10 million years.
How can we return to the safe operating space?
To relieve the pressure on this planetary boundary, we must reduce the many anthropogenic stress factors that ecosystems are exposed to today – by sustainably using the spheres that we share with other forms of life, be it land, inland waters, or the ocean. Climate protection, less pollution, smarter land use planning and more sustainable methods of agriculture, forestry, and fishing are only some of the activities that we can combine to achieve sustainable use.