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Planetary Boundaries~I

Carrying capacity itself is a well-known and widely accepted concept in ecology. It is a basic idea relating to sustainability. It often serves as a basis of sustainable development policies that attempts to balance the needs of today against the resources that will be needed in the future.

Jaydev Jana | New Delhi |


In the early 1970s the Columbia Broadcasting System (CBS) Evening News with Walter Cronkite, an American broadcast journalist, ran a popular series of environmental stories entitled ‘Can the World Be Saved?’ He dramatically presented the much simpler environmental problems of that period to a huge audience and facilitated the formation of a powerful environmental consciousness.

Today, the question ~ ‘Can the World Be Saved?’ ~ is more serious and legitimate than it was then. As we enter the 21st century, human activities are disrupting the great ecological systems and natural cycles that make our planet habitable, bountiful and wondrous.

Back in 1798, Thomas Robert Malthus, an economist and demographer, made a dire prediction. He predicted that the Earth could not indefinitely support an ever-increasing human population. The planet, he said, would check population growth through famine if humans did not check themselves. Changes in population can have a variety of economic, ecological, and social implications. One population concern is that of carrying capacity ~ the number of individuals an ecosystem can support without having any negative effects. Hence, the theory of Malthus appears to be similar to the carrying capacity of Earth. But Malthus was too early to assume that population pressures would automatically reverse the gains of economic development. Indeed, he had no idea about the power of science-based technological advances that would occur after his prediction.

Moreover, he could not foresee the Green Revolution, which would dramatically expand the capacity to grow more food to feed a larger global population. Nor could Malthus have foreseen the demographic transition which means that richer households would choose to have fewer children. Yet his prediction of population explosion was quite right. When he wrote, the world population was around 900 million. Now world population is 7.9 billion. And there is more to come: perhaps up to 10.9 billion by 2100, as predicted by the UN Population Division.

Carrying capacity itself is a well-known and widely accepted concept in ecology. It is a basic idea relating to sustainability. It often serves as a basis of sustainable development policies that attempts to balance the needs of today against the resources that will be needed in the future. Carrying capacity is defined as a species’ average population size in a particular habitat. Of course, carrying capacity need not be fixed and can be expanded through good management and the development of new resource -saving technologies. Compared to areas with a lower standard of living, areas with a higher standard of living tend to have a reduced carrying capacity due to greater access to and demand for more resources.

Humanity has become so numerous and so productive that anthropogenic pressures on the Earth Systems have reached a scale where abrupt global environmental change can no longer be excluded. It means that we are crossing the boundaries of Earth’s carrying capacity, thereby threatening our nature vis-à-vis our survival. The planetary boundary (PB) concept, introduced in 2009 by the world-leading environmental scientist Johan Rockstrom and others, aimed to define the environmental limits within which humanity can safely operate.

The concept challenges the belief that resources are either limitless or infinitely substitutable. They identified and quantified a set of nine planetary boundaries within which humanity can develop and feel good in the future. If we cross these limits, abrupt or irreversible environmental changes can occur with serious consequences for humankinds. The status of each boundary was updated in 2015.

The nine PBs as identified are: (1) Climate change; (2) Ocean acidification; (3) Stratospheric ozone depletion; (4) Biogeochemical flows (Nitrogen and phosphorus cycle); (5) Freshwater use; (6) Land-system change; (7) Change in biosphere integrity (biodiversity loss and species extinction); (8) Atmospheric aerosol loading) and (9) Chemical pollution.

The First and most important PB relates to climate change which is due to the rise of human-induced Greenhouse gases (GHGs) in the atmosphere. The GHGs include Carbon dioxide (CO2), methane, nitrous dioxide, and a few other industrial chemicals. The greater the concentration of GHGs in the atmosphere, the warmer on average the planet Earth. Earth’s climate has changed throughout history. Before the industrial revolution, the Earth’s atmosphere contained about 280 ppm of CO2. As industrialization began to drive up, the level of GHGs, predominantly CO2, began to rise. The global average atmospheric CO2 in 2019 was 409.8 ppm, with a range of uncertainty of plus or minus 0.1 ppm. The levels are higher than at any point in at least the past 800,000 years. The average temperature in 2020 was about 14.9 degrees C, 1.2 degrees C above the pre-industrial (1850-1900) level. It is widely accepted that keeping global temperature rise below 2 degrees C measured from preindustrial levels (1850) is the threshold that will leash climate change from being ‘dangerous’ to becoming ‘catastrophic’. The 2 degrees C is possible only if the world limits GHG concentration at 450 ppm CO2-e taking together the stock and current emissions.

If we consider the atmosphere as a cup of water, filled to the brim, more water can only be filled if the cup is emptied to create space. But since there are many claimants on the water that needs to be filled in the cup, the space will have to be apportioned/budgeted ~ so that the earlier occupiers vacate and the new claimants fill in, in some proportion of equity. We know that concentration of all GHGs emissions is already close to 430 ppm. But with some ‘cooling’ allowance, because of aerosols, it comes to around 400 ppm on an average. Every part of the world is contributing to the problem and climate change affects every part of the planet.

The second PB, ocean acidification, is closely related to the first. Approximately 30 per cent of human-induced CO2 ends up in the oceans, where it dissolves into a weak acid, carbonic acid, building up in such enormous volumes that it has nevertheless already made the world’s oceans more acidic than at any time in the last 55 million years. The rate of acidification is faster than at any time in the last 300 million years. The higher levels of acidity seem to have serious deleterious effects:

(1) The growing absorption of CO2 in the oceans interferes with the reproduction of some species. And among the shell -making creatures at risk are tiny zooplanktons with very thin shells that play an important role in the food chain of ocean bottom.

(2) The higher levels of acidity are reducing the concentration of carbonate ions that are essential to species that make shells and coral reefs.

(3) Global warming and CO2- caused acidification are exacerbating the decline in fisheries and marine biodiversity.

(4) Jane Lubchenco, an American environmental scientist, called the ocean acidification global warming’s ‘evil twin’.

(5) Status as in 2015: still within the boundary.

(To be concluded)