The State We're In
It’s past time to start respecting Earth’s boundaries!
By Alison Mitchell, Co-Executive Director
We all have personal boundaries, the limits and rules we set for our relationships. When others don’t respect our boundaries, there can be trouble!
People aren’t the only ones with boundaries. Mother Earth also has boundaries – the complex systems and processes that keep the planet stable and resilient.
A recent study in the journal Science Advances found that six of the planet’s nine critical boundaries have been crossed due to human activity, suggesting that “Earth is now well outside of the safe operating space for humanity.”
Published last fall by a team of international scientists, the study is yet another wake-up call related to how we are treating our home planet. It builds on a 2009 paper on the constraints needed to keep Earth’s environment similar to the one humans inhabited before our current industrial era began.
“This update on planetary boundaries clearly depicts a patient that is unwell, as pressure on the planet increases and vital boundaries are being breached,” said co-author Johan Rockstrom of the Potsdam Institute for Climate Impact Studies. “We don’t know how long we can keep transgressing these key boundaries before combined pressures lead to irreversible change and harm.”
According to the study, the 10,000-plus year period from the end of the last ice age to the start of the Industrial Revolution was characterized by relatively stable and mild planetary conditions. Human activities over the past 200-plus years, however, have pushed the Earth beyond the previous limits of environmental variability.
Here are the planetary boundaries described in the study:
Climate change – This is the boundary that usually gets the most attention. The study looked at carbon dioxide concentrations in the atmosphere and “radiative forcing,” a measure of the balance between the energy from sunlight hitting the Earth, and the thermal energy the planet loses. The massive increase in atmospheric carbon dioxide caused by our burning of fossil fuels is trapping so much thermal energy that sea level will rise dramatically and ecosystems unravel due to droughts, fires, floods, and other extremes. Yet we’ve practically ignored these warnings for nearly half a century.
Biosphere integrity – Although climate often takes center stage in discussion over Earth’s future, biological integrity is just as critical. The study evaluated biological integrity two ways. The first is genetic diversity, measured by the extinction rate of species. This boundary has been greatly exceeded, as an estimated 10 percent of the Earth’s species were lost in the past 150 years, and a million of our current eight million plant and animal species are threatened with extinction. The second is “functional integrity,” having to do with plant photosynthesis. Prior to the industrial era, only 2 percent of Earth’s photosynthesis served human purposes; now human-centered agriculture and tree plantations comprise 30 percent of the planet’s photosynthetic capability. And for the most part, conventional agriculture and forest plantations are biological deserts that are consuming habitats, eliminating pollinators, and consuming freshwater at unsustainable rates.
Novel entities – This is the term for the synthetic chemicals that have been introduced into the environment, including plastics, nuclear weapons and nuclear waste, pesticides, genetically modified organisms, and the “forever chemicals” known as PFAS (perfluoroalkyl and polyfluoroalkyl substances). Since many novel entities are extremely harmful to biological food webs, entire communities of animals are in cataclysmic decline, as one moves up the food chain from insects to large predators.
Biogeochemical flows – This measure tracks the flows of phosphorus and nitrogen, both widely used as crop fertilizers. When they enter ecosystems, these chemicals can cause damage by, for example, triggering harmful algal blooms. The study found this boundary has been exceeded.
Land system change – This boundary involves land use, specifically forest loss. The researchers believe we need to retain 75 percent of Earth’s forests due to their importance in moderating our climate. But they found that just 60 percent of land once forested remains so. As we approach half of the earth’s terrestrial “lungs” being gone, the rate of climate change will accelerate. Forests are our best tool to absorb carbon dioxide, and globally we are losing the quest to save and restore forest cover.
Freshwater change – This boundary reflects human modification of freshwater systems – both “blue water” (visible in rivers, lakes and other freshwater bodies) and “green water” (invisible water, held in soil and plants). Both boundaries have been transgressed, according to the report.
Stratospheric ozone depletion – This is one area where the planet is improving. This boundary was exceeded in the 1990s, but thanks to global initiatives to reduce use of ozone-depleting chemicals, ozone layer damage is being reversed.
Ocean acidification – The acidity of the ocean is still considered to be in the safe zone, but just barely. “Anthropogenic (human-caused) ocean acidification currently lies at the margin of the safe operating space, and the trend is worsening as anthropogenic CO2 emission continues to rise,” the report said. Excess carbon dioxide in the atmosphere interacts with the ocean surface to make seawater more acidic and less hospitable to the worldwide plankton community that is fundamental to oxygen production and the oceanic food chain.
Atmospheric aerosol loading – This refers to particles in the atmosphere, such as dust and soot. This boundary has not been crossed yet, the report said, but rising pressures are evident in regions where air particle pollution impacts monsoon systems.
As the study makes clear, all systems on Earth – on the land, in the air, and in the water – are connected. The planet has experienced enormous human impacts since the industrial era began, and we’re crossing most limits on how much the planet as we know it can withstand!
This is overwhelming information, but as a civilization, we must reverse our trajectory, restore our ecosystems, reduce carbon in the atmosphere, preserve land and water resources, protect and restore forests, save imperiled species and their habitats, and eliminate harmful chemicals. It won’t be easy, but efforts are underway all across the planet – and we must redouble them!
Here in New Jersey, we’re taking steps to do our part by rapidly transitioning from fossil fuels to clean sources of electricity, continuing as a national leader in preserving natural lands and water resources, planting thousands of trees in rural, suburban and urban areas, protecting and restoring native wildlife and habitats, and much more. We need to increase those efforts – and quickly. The reversal of the damage to the ozone is proof that we can meet these challenges if we take collective action!
To read the report in Science Advances, go to https://www.science.org/doi/10.1126/sciadv.adh2458. For more information on planetary boundaries, go to https://www.pik-potsdam.de/en/output/infodesk/planetary-boundaries.
About the Authors
John S. Watson, Jr.
Michele S. Byers
Executive Director, 1999-2021
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