Scientists have identified nine planetary boundaries that help regulate a livable planet. Human activities have pushed six of those nine critical Earth systems beyond safe limits, threatening the stability of life as we know it.
Mongabay has consistently reported on all nine systems:
Climate change, largely driven by fossil fuel emissions, is causing sea level rise, extreme weather events and wildfires. Ecosystems and wildlife are struggling to adapt to a quickly warming world as the planetary boundary for climate change has passed the threshold of safety.
Biosphere integrity of ecosystems and biodiversity no longer exists as we’ve known it. Biodiversity in the Arctic and tropical ecosystems are particularly vulnerable, and populations of birds, mammals and amphibians are in sharp decline.
Freshwater systems have been so damaged that roughly a quarter of all freshwater species listed on the IUCN Red List are threatened with extinction. Disruption to the water cycle and the lack of aquatic oxygen are endangering human health and freshwater ecosystems.
Biogeochemical flow changes, including shifts in phosphate and nitrogen cycles, are causing an environmental crisis. Synthetic fertilizers produce excess nitrogen, for example, that can run off into water bodies and kill aquatic life.
Land-use change for agriculture and urban development has degraded 15 million square kilometers (5.8 million square miles) of land globally, an area nearly the size of Russia. This surpassed planetary boundary directly impacts seven others.
Novel entities, most notably plastic, have also passed the safe threshold and are impacting other planetary boundaries. Most plastic is made from fossil fuels and is a serious threat to human health, biodiversity, climate change, and both freshwater and oceans.
Atmospheric aerosol loading hasn’t yet crossed its planetary boundary. Aerosol pollution can come from vehicles, factories and power plants, many of the same sources of climate change. Paradoxically, these tiny particles in the atmosphere can cool the Earth by reflecting the sun’s rays, as seen with shipping pollution over the Atlantic Ocean, but negative health effects from air pollution exposure mean it’s not a viable geoengineering option.
Ocean acidification is on the threshold of becoming the seventh planetary boundary transgressed. Increasingly acidic oceans are killing coral and other marine organisms, raising questions about the ocean’s continued ability to support life.
Ozone depletion is the lone success story, stemming from the 1987 Montreal Protocol, which imposed a global ban on 99% of ozone-depleting chemicals. The stratospheric ozone layer that protects all life on Earth from the sun’s radiation is expected to completely recover in the coming decades.
While these converging environmental challenges raise serious concerns for the ability of Earth to continue to support life as we know it, solutions do exist, as Mongabay has reported. These include community-led efforts, technological innovations, greenhouse gas reductions, and geoengineering.
The question on this Earth Day is not can we make appropriate changes, but will we?
Banner image: “Earthrise” the iconic photo that first showed humanity the fragility of Earth, courtesy of NASA.
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