The term biosphere is used to refer to the part of the Earth in which living things live. The interactions between the Earth and the biosphere play an important role in regulating the conditions on Earth. The main factor that enables the biosphere to fulfil this function is genetic diversity. Yes, genetic diversity. Therefore, in order to measure the integrity of the biosphere, it is necessary to take into account its genetic diversity as well as its planetary function.
In the past, planetary boundaries regarding biodiversity have been linked to the rate of species extinction. Although it is not easy to obtain precise numbers about the rate at which species went extinct in the distant past, it is estimated that the current rate of species extinction is tens or even hundreds of times the average over the last ten million years.
Today, the biosphere is thought to be home to approximately 8 million plant and animal species. Approximately one million of these species are at risk of extinction. The genetic diversity of plant and animal species may have decreased by more than 10% over the last 150 years.
The limit that should not be exceeded in terms of genetic diversity is defined as 10 extinctions per million species per year. In other words, the ratio of the number of species that become extinct each year to the total number of species should not exceed 10 per million. It is stated that the current value of this rate is over 100 per million, even according to the most optimistic estimates.
The functionality of the biosphere is associated with net primary production (the flow of matter and energy provided to the biosphere by photosynthesis). The criterion that must be taken into account to maintain functionality is the share that people receive from primary production.
When it comes to terrestrial primary production, scientific studies show that the Holocene average is around 55.9x109 tons of carbon per year. In other words, the ratio of the number of species that become extinct each year to the total number of species should not exceed 10 per million. It is stated that the current value of this rate is over 100 per million, even according to the most optimistic estimates.
The functionality of the biosphere is associated with net primary production (the flow of matter and energy provided to the biosphere by photosynthesis). The criterion that must be taken into account to maintain functionality is the share that people receive from primary production.
When it comes to terrestrial primary production, scientific studies show that the Holocene average is around 55.9x109 tons of carbon per year. Moreover, the oscillations at this level are very small. Annual changes do not exceed 1.1x109 carbon per year. The analysis concludes that primary production around 1700 was also close to Holocene values. Around 1700, "potential natural" net primary production was around 56.2x109 carbon per year. When land use is taken into account, this value drops to 54.7x109 carbon per year. By 2020, potential natural net primary production could be as high as 71.4x109 carbon/year, as atmospheric carbon dioxide increases photosynthesis. However, due to the increase in global land use, net primary production remained at 65.8x109 carbon per year.
The human share of primary production includes both the harvested agricultural production and the human modification (or rather reduction) of net primary production due to agriculture, afforestation, and grazing. The share of humans in primary production can be calculated according to the Holocene averages before the Industrial Revolution or according to the current potential primary production values. However, today's potential primary production increase is largely due to excess carbon dioxide accumulation in the atmosphere, and current excess production must be preserved and not harvested to mitigate the effects of global warming. Therefore, it is more accurate to calculate the share of humans in net primary production according to pre-industrial Holocene averages. According to the researchers, a safe value for the human share of net primary production might be 10%. It is considered dangerous if this value exceeds 20%. In the early Holocene, the human share of primary production was around 2%. Today, this rate has risen to 30%. It is stated that the danger limit began to be exceeded in the late 1800s.
People meet their needs such as food, clothing, and animal feed with the share they receive from primary production, and will continue to do so. For a more sustainable future, net primary production needs to increase. It is estimated that the world can safely feed ten billion people. However, for this to happen, scientific and technological developments are needed.
Ozone Depletion:
The ozone (O3) layer in the atmosphere protects the earth from harmful rays coming from the sun. In the 1980s, thinning of the ozone layer was detected in the parts of the Earth above Antarctica. Scientific studies have shown that this thinning is caused by CFCs and various other chemicals that are unconsciously released into the atmosphere. The ozone layer began to heal after the Montreal Protocol imposed restrictions on the production of ozone-depleting materials in 1987.
To express the amount of ozone in the atmosphere, the Dobson unit (DU) is used, which represents the amount of matter remaining in an imaginary column rising from a point on the earth's surface. Before the Industrial Revolution, the amount of ozone in the atmosphere was 290 DU. The limit value that should not be exceeded (should not fall below) for the amount of ozone is accepted as 276 DU. Today, the amount of ozone in the atmosphere is approximately 284 DU. Therefore, although the amount of ozone in the atmosphere is not as high as it was before the Industrial Revolution, it is within the safe zone. The limit values are now only exceeded during the 3-month periods when spring is experienced in the Southern Hemisphere and only in the regions above Antarctica. The recovery of the ozone layer is expected to continue in the future.