The largest on earthEcosystemsYesBiosphere(biosphere), which encompasses an integrated system of all forms of life on earth and its living environment. From deep oceans to high mountain ranges, from hot deserts to cold polar regions, the biosphere covers the earth's surface and the conjoining regions of the atmosphere, water and rocky circles surrounding it. This vast and complex system not only supports the survival of millions of species, but also maintains the balance of life on earth through energy flows and material cycles。
Composition and scope of the biosphere
Biosphere boundaries are not fixed, but are generally considered to extend vertically from the deepest depths of the seabed (e. G., mariana trench, about 11,000 metres) to the stratosphere (about 10 kilometres above). Horizontally, the biosphere covers three major ecosystems, terrestrial, freshwater and marine:
1. Terrestrial ecosystems: including forests, grasslands, deserts, tundra, etc. Tropical rainforests are the most biodiversity-rich region on land and, although they account for only 6 per cent of the earth's surface, they host more than half of the world's species。
Freshwater ecosystems: rivers, lakes, wetlands, etc. Wetlands are referred to as the “renals of the earth” and have the function of water purification and climate regulation。
3. Marine ecosystems: 71 per cent of the earth's surface area, with an average depth of 3,800 metres. Although they account for only 0. 1 per cent of the ocean area, coral reefs provide a habitat for 25 per cent of marine life and are “tropical rainforests in the oceans”。
The function and importance of the biosphere
The biosphere sustains life on earth through four core functions:
Energy flows: solar energy drives the functioning of ecosystems through photosynthesis into the food chain. For example, phytoplankton fixes about 50 billion tons of carbon per year, or 50 per cent of global photoco-operation。
2. Material cycle: carbon, nitrogen, water and other elements cycling between biological and abiotic environments. The oceans absorb about 25 per cent of human carbon dioxide emissions per year, slowing downClimate changeI don't know。
3. Biodiversity: some 8. 7 million organisms (estimated by plos biology) exist in complex ecological networks, where microorganisms account for 60 per cent of the total biological population and are key to the breakdown and nutrient cycle。
4. Eco-services: the united nations millennium ecosystem assessment states that the biosphere provides approximately $12. 5 trillion annually in value for ecological services, including food production, climate regulation and cultural values。
Impact of human activities on the biosphere
Since the industrial revolution, humankind has significantly changed the balance of the biosphere by:
- habitat destruction: the global forest area is reduced by about 10 million hectares per year (fao data), resulting in species extinction rates 100-1,000 times higher than natural background values。
- climate change: atmospheric co2 concentrations have risen from 280 ppm before industry to 420 ppm (2023 data), triggering extreme weather and ocean acidification。
- pollution: about 8 million tons of plastics enter the sea every year, threatening 90 per cent of seabirds and 30 per cent of turtles (united nations environment programme report)。
Global action for the protection of the biosphere
The international community has taken a number of measures to address the ecological crisis:
Convention on biological diversity: the “quinming-montreal framework”, adopted in 2022, sets a target of 30 per cent protection of land and oceans by 2030。
Carbon neutrality and commitment: 137 countries have established carbon neutrality timetables and china plans to achieve this by 2060。
3. Ecological rehabilitation: china's reforestation project has accumulated 32 million hectares, 100 times the size of belgium。
Future outlook
The stability of the biosphere depends on humans turningSustainable developmentMode. The combination of technological innovations (e. G. Clean energy, vertical agriculture) and traditional wisdom (e. G. Ecological management in indigenous communities) may be key. As the ecologist barry conmaner said: “the earth's ecosystem is a whole, and any local destruction will ultimately affect the whole picture. Only global collaboration can ensure that this largest ecosystem continues to feed all。
