As a biogeographer with decades-long interest in Earth’s ecosystems, I have grave concerns for the future of our planet’s biosphere. Human activities are pushing the living systems of Earth to the brink of collapse. It is prudent to consider and plan for the worst-case scenarios that may develop.
The biosphere – the thin layer of life encompassing our planet – is under assault. Our activities are disrupting every level of biological organization, from genes to ecosystems. The general response of the biosphere to these impacts is one of simplification, homogenization, and collapse (Bland et al. 2018, McGuire 2022).
Soil degradation is widespread (Amundson et al. 2015), and at the microbial level, we’re seeing alarming shifts in soil and marine microbiomes. The overuse of antibiotics and agricultural chemicals is creating resistant superbugs while decimating beneficial microorganisms. In the oceans, warming and acidification are disrupting phytoplankton communities, the base of marine food webs (Bijma et al. 2013, Gronniger et al. 2022). The consequences ripple up through entire ecosystems.
Plant communities are struggling to adapt to transforming climatic conditions (Franklin et al. 2016, Pausas and Bond 2020). We’re witnessing widespread forest dieback events, from the Amazon to the boreal forests. Drought-stressed trees are succumbing to pests and diseases at unprecedented rates. Losing these carbon sinks further accelerates climate change in a vicious feedback loop.
Animal populations are in freefall. The current extinction rate is estimated to be 100 to 1000 times higher than the background rate. Large mammals, apex predators, and specialist species are especially vulnerable, but smaller creatures are also susceptible (Wagner et al. 2021). The cascading effects of these losses are reshaping entire ecosystems (Ceballos et al. 2010, De Vos et al. 2015, Stork 2010).
Perhaps most alarmingly, we are seeing the collapse of entire biomes. Coral reefs, for instance, may be largely gone within a few decades because of ocean warming and acidification. The Arctic tundra is rapidly transforming as permafrost thaws, releasing massive amounts of stored carbon and methane.
A worst-case scenario may occur as a cascading series of tipping points lead to a “Hothouse Earth” (Dakos et al. 2019, McGuire 2022, Moore 2018, Munson et al. 2018, Ritchie et al. 2021, Schroeder and Storm 2020, Selkoe et al. 2015, Steffen et al. 2018). In this future, large parts of the Earth will become uninhabitable for most large animals, including humans. Vast swathes of the tropics will become too hot for trees, transforming into barren wastelands. The collapse of major ecosystems like the Amazon rainforest or the Antarctic ice sheets will trigger abrupt, irreversible changes to the Earth system (Chen et al. 2020, Wang et al. 2020).
We will see a dramatic simplification of the biosphere. Complex ecosystems will give way to hardier, generalist species (D’Antonio and Vitousek 1992). Biodiversity will plummet, with devastating consequences for ecosystem services we take for granted – from air pollination to water purification (Cardinale et al. 2012, Isbell et al. 2015, Tekalign et al. 2017).
With increased acidification and heat, the oceans will become dominated by jellyfish and algae as higher trophic levels collapse (Doney at al. 2020, Poloczanska et al. 2016). On land, invasive species and hardy generalists will thrive in the disturbed landscapes (Franklin et al. 2016). The Earth’s biological systems could reach a new, much less diverse and productive equilibrium that would persist for millions of years.
The trajectory we are on leads to an impoverished, unstable biosphere that may be incapable of supporting complex human civilizations (https://garryrogers.com/2024/07/15/worst-case-climate-change-scenario/).
The window for avoiding the worst outcomes is about to close. We need immediate, drastic action to reduce our impact on the planet’s living systems. Without it, we risk pushing the biosphere beyond tipping points from which recovery, on any timeframe meaningful to our species, may be impossible (Dakos et al. 2019). I honestly do not expect that we will take action.
Biosphere decline has been developing for decades and it is no longer news. It’s time we start planning our role in the diminished human civilization that is coming (https://garryrogers.com/2024/07/25/can-we-survive-climate-change/).
References
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