A Safe operating space for humanity
As in the “Holocene” epoch, environmental change occurred naturally and all the natural variables like temperature, freshwater availability & biogeochemical flows stayed within the range, which enabled to maintain a stable human development. While in the “Anthropocene” epoch, environmental change occurred un-naturally due to a rapid growth of industries, factories, agricultures, human actions across the world, which affect the earth systems/natural variables that keep earth in the desirable Holocene epoch. If this phenomena do not stop then the existence of whole human beings will fall in danger because if the natural variables abrupt then the human civilization will also be abrupt.
So, to keep a balance in the earth system & to keep continue Holocene epoch, Johan Rockstrom and Colleagues propose a framework based on global “biophysical boundaries” that strongly represent a safe operating space for humanity with respect to Earth system that will allow human civilization to arise , develop, and thrive in future.
Many subsystems on earth react in non-linear way & are particularly sensitive around the thresholds level of certain variables. To continue to live and operate safely human beings have stayed away from the thresholds in earth’s environment. Here, “thresholds” means a nonlinear changes from desired to undesired state. If these thresholds are crossed then the rapid & unpredictable environmental change might produce some dangerous results but if we respect them, then we have a bright future for centuries ahead.
So, Johan Rockstrom and colleagues again tried to identify the earth system processes and its associated thresholds which, if crossed, could generate unacceptable environmental change. Finally the authors proposed nine such variable for human habitations which is necessary to define planetary boundaries: climate change; rate of biodiversity loss (terrestrial and marine); interference with the nitrogen and phosphorous cycles; stratospheric ozone depletion; ocean acidification; global freshwater use; change in land use; chemical pollution; and atmospheric aerosol loading. Here, planetary boundaries are human made values of control variable fixed at a ‘safe’ distance from dangerous levels or from its evidence of thresholds. Authors have taken a conservative, risk-averse approach to quantifying the planetary boundaries, taking into account the large uncertainties that surround the true position of several thresholds. The selection of control variables for each planetary boundary is based upon assessment of the variables that may provide the most comprehensive, aggregated and measurable parameter for individual boundaries.
After analyzing & identifying the above mentioned planetary boundaries, authors also suggested that three of the earth system processes: climate change, rate of biodiversity loss, and interference with the nitrogen cycle, have already transgressed their boundaries.
I agree with authors view, they define habitability in terms of “safe operating space for humanity” to identify & quantify planetary boundaries, really they alerted us to sharing reality of natural variables but apart from these, they didn’t select human ethical, moral behavior because it also affect nature somewhere else invisibly, it may have certain boundaries limit.
Justification & quantifying of planetary boundaries:-
Climate change: The climate change boundary has currently become a debatable topic at international level because day to day concentration of CO2 increases at moderate rate. It has two parameters: atmospheric concentration of CO2 and radiating forcing (the rate of energy change per unit area of the globe as measured at the top of the atmosphere).Authors also predicted that CO2 concentration should not exceed 350 ppm by volume, and radiating forcing should not exceed 1 watt/square meter but currently both have crossed the limit. There are three reason for proposed climate boundaries: first is to maintain equilibrium between the climate system and greenhouse gases; second is to attain stability of the large polar ice sheets; third is to stop earth subsystem moving outside to Holocene state.
Rate of biodiversity loss: It happens due to species extinction. Currently the rate of extinction of species is 100 to 1,000 times. Change in land use exert the most significant effect. These changes include growing of agriculture, urban etc. But all these things are necessary to keep balance on increasing population of the world. As the author says 30% of all mammals, birds and amphibian species have been threatened with extinction in one year. Its impact is found from local to regional level. In my point of view biodiversity loss will continue to fulfill the requirement but we have to overcome it by increasing plantation & greenery across the world.
Nitrogen and Phosphorus cycles: Modern agriculture plays a vital role in environmental pollution. It is show due to the use of nitrogen and phosphorus on large scale as fertilizers. As data shows that 120 million tonnes of N2 fertilizers are manufactured from the atmosphere per year for food production, which is more than the combined effects from all earth terrestrial processes. Where Nitrous oxide is one of the most important non CO2 greenhouse gases which directly increases radiating force. Unlike Nitrogen, the use of phosphorus is also required as fertilizers & some chemicals. Some data shows that 20 million tonnes of phosphorus is mined every year and around 8.5 to 9.5 million tonnes of it finds into the oceans.
Therefore, Authors proposed nine planetary boundaries which define biophysical precondition for human development. He also argued that natural variable should not cross biophysical thresholds range, which is dangerous for humanity. “If one boundary is transgressed, then other boundaries are also under serious risk”.
Tell us your learning needs in detail and get immediate response from qualified tutors