An acceleration of ecosystem collapse

An acceleration of ecosystem collapse

Around the world, rainforests are becoming savanna or farmland, savanna is drying out and turning into desert, and icy tundra is thawing. Indeed, scientific studies have now recorded « regime shifts » like these in more than 20 different types of ecosystem where tipping points have been passed. Around the world, more than 20% of ecosystems are in danger of shifting or collapsing into something different. These collapses might happen sooner than you’d think. Humans are already putting ecosystems under pressure in many different ways—what we refer to as stresses. And when you combine these stresses with an increase in climate-driven extreme weather, the date these tipping points are crossed could be brought forward by as much as 80%. This means an ecosystem collapse that we might previously have expected to avoid until late this century could happen as soon as in the next few decades. That’s the gloomy conclusion of an article published in Nature Sustainability[1].

In reality, the models have probably underestimated the impact of a given level of warming on ecosystems. As a result, ecosystem collapse could happen 80% sooner than was imagined with less volatile models. Human population growth, increased economic demands, and greenhouse gas concentrations put pressures on ecosystems and landscapes to supply food and maintain key services such as clean water. The number of extreme climate events is also increasing and will only get worse. What really worries us is that climate extremes could hit already stressed ecosystems, which in turn transfer new or heightened stresses to some other ecosystem, and so on. This means one collapsing ecosystem could have a knock-on effect on neighboring ecosystems through successive feedback loops: an « ecological doom-loop » scenario, with catastrophic consequences.

Across the planet, rainforests are turning into savannas or farmland, while savannas are experiencing drying out and transitioning into deserts. Simultaneously, icy tundra regions are thawing at an alarming rate. These “tipping points” have already been recorded in over 20 types of ecosystems, with others likely to follow the same path. The problem with these tipping points is that once you get to one, there’s no turning back. It gets even worse: a new study has found these collapses could happen sooner than previously expected. Extreme weather events such as droughts and floods will likely accelerate change in ecosystems, leading to faster tipping points. In some systems, adding extreme events on top of other stresses could bring forward the timing of a tipping point by as much as 80%. A combination of continuous stressors such as unsustainable land use, agricultural expansion, and climate change, along with disruptive events like floods and fires, will converge like a « perfect storm », the researchers said. This convergence poses a significant and imminent threat to natural systems, escalating their vulnerability at a rapid pace. « While it’s not currently possible to predict how climate-induced tipping points and the effects of local human actions on ecosystems will connect, our findings show the potential for each to reinforce the other. Any increasing pressure on ecosystems will be exceedingly detrimental. » Since 1980, there’s been a rise in the frequency of extreme climate events, and this is anticipated to escalate further with global warming, even if it is limited to 1.5°C, the goal of the Paris Agreement. The researchers are concerned over ripple effects, where the collapse of an ecosystem could trigger adverse consequences on neighboring ones. An example is the Amazon rainforest. The UN International Panel on Climate Change (IPCC) estimates a tipping point prior to 2100. However, the new study suggests this could happen several decades earlier. Extreme weather events could decrease the Amazon’s ability to regenerate its own rainfall, making it drier and more vulnerable.

How long until a collapse? In its new research, Simon Willcock[2] wanted to get a sense of the amount of stress that ecosystems can take before collapsing : « We did this using models—computer programs that simulate how an ecosystem will work in future, and how it will react to changes in circumstance. We used two general ecological models representing forests and lake water quality, and two location-specific models representing the Chilika lagoon fishery in the eastern Indian state of Odisha and Easter Island (Rapa Nui) in the Pacific Ocean. These latter two models both explicitly include interactions between human activities and the natural environment. »

The key characteristic of each model is the presence of feedback mechanisms, which help to keep the system balanced and stable when stresses are sufficiently weak to be absorbed. For example, fishers on Lake Chilika tend to prefer catching adult fish while the fish stock is abundant. So long as enough adults are left to breed, this can be stable. However, when stresses can no longer be absorbed, the ecosystem abruptly passes a point of no return—the tipping point—and collapses. In Chilika, this might occur when fishers increase the catch of juvenile fish during shortages, which further undermines the renewal of the fish stock. They used the software to model more than 70,000 different simulations. Across all four models, the combinations of stress and extreme events brought forward the date of a predicted tipping point by between 30% and 80%. This means an ecosystem predicted to collapse in the 2090s owing to the creeping rise of a single source of stress, such as global temperatures, could, in a worst-case scenario, collapse in the 2030s once they factor in other issues like extreme rainfall, pollution, or a sudden spike in natural resource use. Importantly, around 15% of ecosystem collapses in their simulations occurred as a result of new stresses or extreme events, while the main stress was kept constant. In other words, even if we believe we are managing ecosystems sustainably by keeping the main stress levels constant—for example, by regulating fish catches—we had better keep an eye out for new stresses and extreme events.

Global warming is worsening much faster than predicted, and its effects are amplifying. Temperature records are being broken around the world. Terrifying studies are piling up. Our planet threatens to become uninhabitable. A major concern for the world’s ecosystems is the possibility of collapse, where landscapes and the societies they support change abruptly. Accelerating stress levels, increasing frequencies of extreme events and strengthening intersystem connections suggest that conventional modelling approaches based on incremental changes in a single stress may provide poor estimates of the impact of climate and human activities on ecosystems.

Previous studie[3] indicated that the substantial costs associated with surpassing tipping points in vast ecosystems would primarily manifest in the latter half of this century. However, the researchers now believe these costs may materialize much earlier than previously anticipated. This brings new challenges for governments around the world as climate change kicks in. There is no way to restore collapsed ecosystems within any reasonable timeframe. There are no ecological bailouts. In the financial vernacular, we will just have to take the hit.

[1] Willcock, S., Cooper, G.S., Addy, J. et al. Earlier collapse of Anthropocene ecosystems driven by multiple faster and noisier drivers. Nat Sustain (2023). Published 22 June 2023 – DOI
[2] Ibid
[3] « Risk of multiple interacting tipping points should encourage rapid CO2 emission reduction » Cai, Y., Lenton, T. & Lontzek, T. Risk of multiple interacting tipping points should encourage rapid CO2 emission reduction. Nature Clim Change 6, 520–525 (2016).