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Independent Professional: Experienced educator and management consultant for engineering educational institutions, researcher, trainer, technical consultant on sustainable technologies, related to cement manufacturing and characterisation, using industrial and agricultural wastes in cement and concrete, durability of concrete and fuel cell power.

Monday, October 5, 2009

Earth too has limits

Out of the nine biophysical thresholds that must be observed in order to prevent disastrous consequences for humanity, we've already surpassed three, according to a feature article published in Nature (see Ref.). The report looked at nine different metrics including climate change, ocean acidification, and global freshwater use and estimated for each the degree to which we have approached or surpassed the critical threshold. Loss of biodiversity and alterations to the nitrogen cycle have progressed far past the point of safety, with climate change also exceeding its limit.

During the Holocene state, environmental change occurred naturally and Earth's regulatory capacity maintained the conditions that enabled human development. Regular temperatures, freshwater availability and bio-geo-chemical flows all stayed within a relatively narrow range. Now, largely because of a rapidly growing reliance on fossil fuels and industrialized forms of agriculture, human activities have reached a level that could damage the systems that keep earth in the desirable Holocene state. The result could be irreversible and, in some cases, abrupt environmental change, leading to a state less conducive to human development. Without pressure from humans, the Holocene is expected to continue for at least several thousands of years.

The authors tried to identify the Earth-system processes and associated thresholds which, if crossed, could generate unacceptable environmental change. They found nine such processes for which we believe it is necessary to define planetary boundaries, namely climate change; rate of biodiversity loss (terrestrial and marine); interference with the nitrogen and phosphorus cycles; stratospheric ozone depletion; ocean acidification; global freshwater use; change in land use; chemical pollution; and atmospheric aerosol loading.

Ref: Johan Rockström et. al., "A safe operating space for humanity", Nature, Vol. 461, September 2009, pp 472 -475 | doi:10.1038/461472a


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