The nine planetary boundaries are:
- Stratospheric Ozone Depletion: The stratospheric ozone layer in the atmosphere filters out ultraviolet (UV) radiation from the sun. If this barrier thins, ultraviolet radiation will reach the ground and damage terrestrial and aquatic ecosystems, causing increased occurrences of skin cancer in humans. The reduction of the Antarctic ozone hole was proof that thinning can and will occur if we do not remain on the path set by the Montreal Protocol Treaty.
- Biosphere Integrity: The rate of biodiversity loss (terrestrial and marine) has escalated in the past 50 years, driven primarily by land use change for industrial agricultural use. This has resulted in ecosystem damage and species extinction. When a species goes extinct, its function in the web of life is lost. If, for example, the extinct species is a key crop pollinator, you can imagine the damage done to farmers and the ability to feed people. Research is underway to gather data and understand variables that will help shape a boundary.
- Chemical Dispersion and the release of novel entities: Emissions of toxic and long-lived substances such as synthetic organic pollutants, heavy metal compounds and radioactive materials represent some of the key human-driven changes to the planet. These compounds can have potentially irreversible effects on living organisms and on the physical environment (by affecting atmospheric processes and climate). Even when the uptake and bioaccumulation of chemical pollution is at sub-lethal levels for organisms, the effects of reduced fertility and the potential of permanent genetic damage can have severe effects on ecosystems far removed from the source of the pollution. Persistent organic compounds have caused dramatic reductions in bird populations and impaired reproduction and development in marine mammals. Further research is needed.
- Climate Change: This planetary boundary has likely already been transgressed, as evidenced by the loss of summer polar ice. Continued pressure through deforestation techniques (especially tropical rainforests) will push Earth's systems past the tipping point. A precautionary approach would be to not continue on this path to avoid potentially cataclysmic consequences.
- Ocean Acidification: Oceans absorb a quarter of human CO2 emissions, transforming them into carbonic acid and altering ocean chemistry and water pH. This process is devastating to coral and plankton populations, which are critical to a balanced, functioning ocean. Upsetting the bottom of the food chain can pull the rug out from under the entire food pyramid. While all the boundaries are closely linked, ocean acidification is directly associated with and a result of climate change.
- Freshwater Use: Human consumption is directly responsible for the loss of freshwater supplies. It is estimated that by 2050, approximately half a billion people will suffer from lack of access to freshwater. A boundary has been proposed to help manage local, regional, and continental needs.
- Land-system Change: The global population continues to grow by the billions. Agricultural development to feed this population has caused the destruction of forests, wetlands, prairies, and other vegetation systems. This alters water flows and the natural cycling of carbon, nitrogen, and phosphorus in soil. In developing a boundary, the function, quality, and spatial distribution of a tract of land must be considered.
- Biochemical Flows (Nitrogen and Phosphorus Cycling): Human industry and agricultural practices have altered natural cycles of these two elements, both of which are essential to plant growth. Human activity converts exorbitant amounts of atmospheric nitrogen into reactive nitrogen, which pollutes waterways and coastal zones. Over application of phosphorus fertilizers can have huge regional impacts; such as killing off shrimp populations in the Gulf of Mexico or creating dead zones in the oceans.
- Atmospheric Aerosol Loading: This boundary is proposed to combat the effects of aerosols on Earth's climate system. Aerosols interact with water vapor and affect cloud formation and global and regional atmospheric circulation. Each year, an estimated 800,000 people die from consistently breathing aerosol-polluted air. However, interactions between aerosols and the atmosphere are complex, and this has hindered the clear characterization of this boundary.
In summary, we depend daily on biophysical processes for the food on our plate and the air we breathe. We are embedded in and connected to life support systems like biodiversity and eight others. Increasingly, bankers and investors get this connection. An injury to another species is an injury to humanity. The market must stop investing in industries destructive to the planetary boundaries if we are to support continued existence!
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