Earth has ‘high BP’: Why humans breaching most of the planetary boundaries matters

The broken boundaries show Earth’s life-support systems have been driven far away from the safe operating space for humanity that existed during the Holocene period. The period, which began with the end of the last ice age (about 10,000 years ago) and during which modern civilizations evolved, was characterised by relatively stable and warm planetary conditions.

The study, ‘Earth beyond six of nine planetary boundaries’, has been carried out by a team of 29 scientists from eight different countries and published in the journal Science Advances.

What are the planetary boundaries?

Planet boundaries are a framework that identifies guardrails for humanity’s impacts on the Earth system. Put simply, it sets limits on how much humans can be allowed to impact not only the climate but also other global processes that are essential for maintaining conditions on the planet to support modern civilisations.

“We humans (just like all other living organisms) survive by using the Earth’s resources, but those resources are limited. When we acknowledge the Earth’s resources as the currency that supports us, then the planetary boundaries framework becomes a kind of bank statement — it tells us how much of various components (resources) of the Earth system we can allow ourselves to use without greatly increasing the risk that our activities will lead to dramatic changes in the overall environmental conditions we enjoy,” Katherine Richardson, professor of biological oceanography at the University of Copenhagen (Denmark) and lead author of the study, tells The Indian Express over email.

An aerial view of the icebergs near Kulusuk Island, off the southeastern coastline of Greenland, a region that is exhibiting an accelerated rate of ice loss. (Credits: NASA Goddard Space Flight Center)

Developed in 2009, the framework includes nine planet boundaries that scientists believe capture all of the processes critical for maintaining the Earth’s system state. “For each of the boundaries, control variables are chosen to capture the most important anthropogenic influence at the planetary level of the boundary in focus,” the study mentions.

These boundaries and their control variables are:

• Biosphere integrity: The health of ecosystems and rate of extinction of species.
• Climate change: Atmospheric CO2 concentration and the change in radiative forcing — a measure of the balance of energy from sunlight that hits Earth, in comparison with thermal energy the planet loses.
• Novel entities: Levels of plastic, concrete, synthetic chemicals, gene-modified organisms, etc. that would not be found on Earth if we humans were not here.
• Stratospheric ozone depletion: The anthropogenic release of manufactured chemicals that destroy ozone molecules.
• Freshwater change: It includes an examination of the human-induced impact on blue water (found in lakes, rivers, and reservoirs) and green water (available in the soil for plants and soil microorganisms)
• Atmospheric aerosol loading: Tracking various particles from anthropogenic emissions that affect cloud formation as well as global and regional atmospheric circulation.
• Ocean acidification: Reduction in the pH of the ocean over an extended period of time.
• Land system change: Changes in land use, especially the conversion of tropical forests to farmland.
• Biogeochemical flow: Alteration in the natural flows and the forms of nitrogen and phosphorus cycles, which are essential elements for plant growth.

What are the findings of the study?

Out of the nine planetary boundaries, humans have breached six: climate change, biosphere integrity, freshwater change, land system change, biogeochemical flows and novel entities. While atmospheric aerosol loading and ozone depletion remain within the constraints, ocean acidification is close to being breached.

(Express graphic)

One of the most concerning evaluations is the overflow of nitrogen and phosphorus — the biogeochemical flow boundary — in the environment. Although nitrogen and phosphorus are essential for life, their widespread use as crop fertilisers is wreaking havoc by, for instance, triggering algal blooms (it can cause entire fish populations to leave an area or even die) and ocean dead zones (a reduced level of oxygen in the water).

Researchers have also noted that the biosphere integrity boundary was violated in the last 19th century when acceleration in land use caused a strong impact on numerous species. In the case of freshwater, the boundary was breached last century, between 1905 and 1929.

The World Health Organization cites air pollution as responsible for about 7 million deaths yearly around the world. (Credits: NASA)

Another alarming finding is the rising levels of novel entities in the environment. Humans have been releasing unprecedented amounts of synthetic chemicals like pesticides and plastic, without adequate safety testing for decades. This is destabilising and harming the Earth’s system.

Among the violated boundaries, there is also the land system change. “Land-use conversion and fires are causing rapid change in forest area, and deforestation of the Amazon tropical forest has increased such that it has now transgressed the planetary boundary,” the study says.

For climate change, the analysis notes that both the atmospheric CO2 concentration and radiative forcing are steadily increasing. For instance, CO2 concentration currently stands at 417 parts per million (ppm), whereas it was just 280 ppm before the Industrial Revolution. Its safe boundary limit is 350 ppm, which was breached in the 1980s.

Can Earth’s health still recover?

Yes, it can.

“Planetary boundaries do not represent tipping points or thresholds (crossing tipping points can lead to large and often irreversible changes in the climate system). I think of them being more like blood pressure. If your BP is greater than 120/80, it is not a guarantee of your having a heart attack but it does increase the risk and the doctor, therefore, will try to bring it down.

The “blood pressure like” signals we are getting from patient Earth suggest that treatment is necessary to preserve the Earth conditions we are dependent upon,” Richardson says.

Therefore, if humans do away with fossil fuel burning and end destructive farming, the transgressed boundaries can be brought back into “space operating space”.

Notably, the one improving boundary, the stratospheric ozone depletion boundary, is recovering owing to the combined international efforts initiated by the Montreal Protocol in 1987. Researchers say this level of coordinated change may help in dealing with other boundaries.