Rapid environmental change can threaten even a peaceful Daisyworld
A basic model highlights the hidden potential vulnerability of our ecosystems.
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Daisyworld is a basic planet filled with two kinds of daisies that together regulate the temperature to maintain ideal conditions. If the planet heats up or cools down too quickly, all the daisies will go extinct, even if they would otherwise have been able to survive just fine under those conditions. This discovery mirrors similar observations found in other models and observed in real-life ecosystems.
view moreCredit: Hannah Daniel/AIP
WASHINGTON, Feb. 18, 2025 – Imagine a world filled only with daisies. Light-colored daisies reflect sunlight, cooling down the planet, while darker daisies absorb sunlight, warming it up. Together, these two types of daisies work to regulate the planet’s temperature, making the world more habitable for all of them.
And yet, even in this flowery paradise, a simple change can cause the entire ecosystem to collapse.
In Chaos, by AIP Publishing, researchers from the University of Cambridge and University College Cork found that this simple daisy-filled ecological model was vulnerable to collapse after experiencing relatively small, but rapid, changes to the environment.
The hypothetical planet full of daisies is more than an idle curiosity. It has a name — Daisyworld — and was invented in the 1980s as a model to help scientists understand how organisms could help regulate their environment. Since then, researchers have used it to explore topics like biodiversity and climate change.
“The Daisyworld model is a classic thought experiment regarding the co-evolution of life and the environment and has been widely used in the teaching of Earth system science,” said author Constantin Arnscheidt.
Because of its basic and fundamental nature, the authors wanted to use it to study the idea of ecological tipping points, points of no return beyond which an ecosystem is doomed to collapse. This can occur if the environment gets too extreme, but it can also happen if the environment changes too fast. This second type of tipping point is what they were interested in.
“Essentially, if you push the system quickly enough, you can trigger a collapse even if you don’t push it that hard,” said Arnscheidt. “This is called rate-induced tipping: The rate of change is the key factor in determining whether the system tips.”
Using mathematical modeling, the authors discovered that rate-induced tipping can happen even in Daisyworld. If the planet heats up or cools down too quickly, all the daisies will go extinct, even if they would otherwise have been able to survive just fine under those conditions.
This discovery mirrors similar observations found in other models and observed in real-life ecosystems.
“Rate-induced tipping has been shown to be relevant in more and more systems, especially complex ones like those in Earth science and ecology,” said Arnscheidt. “It’s also a phenomenon that will likely be quite relevant for humanity as we continue to navigate an era marked by rapid human-driven rates of change.”
Understanding rate-induced tipping is crucial because these collapse conditions are less obvious, but just as deadly. Without a clear picture of how these ecosystems respond to rapid environmental changes, we could unwittingly doom far more than a planet of hypothetical daisies.
“The fact that we can find rate-induced tipping in a model as classic and well-studied as Daisyworld, more than four decades since its inception, suggests that rate-induced tipping might be present in many other classic models if we only look for it,” said Arnscheidt.
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The article “Rate-induced biosphere collapse in the Daisyworld model” is authored by Constantin W Arnscheidt and Hassan Alkhayuon. It will appear in Chaos on Feb. 18, 2025 (DOI: 10.1063/5.0240983). After that date, it can be accessed at https://doi.org/10.1063/5.0240983.
ABOUT THE JOURNAL
Chaos is devoted to increasing the understanding of nonlinear phenomena in all areas of science and engineering and describing their manifestations in a manner comprehensible to researchers from a broad spectrum of disciplines. See https://pubs.aip.org/aip/cha.
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Journal
Chaos An Interdisciplinary Journal of Nonlinear Science
Article Title
Rate-induced biosphere collapse in the Daisyworld model
Article Publication Date
18-Feb-2025
Why ‘leaky’ plants could accelerate climate change
University of British Columbia
Plants play a key role in regulating Earth’s climate, but recent research suggests that rising temperatures could disrupt this balance, because plants are leaking more water than previously thought.
UBC assistant professor Dr. Sean Michaletz, a newly minted Sloan Research Fellow in the department of botany, studies how plants respond to heat. His findings challenge a long-standing assumption about plant water loss and could change how climate models predict future warming.
What do “leaky” plants have to do with climate change?
Our entire biosphere depends on plants. During photosynthesis, plants absorb carbon dioxide through tiny pores in their leaves and, using light, ‘breathe out’ water vapour and oxygen in an exchange. Since carbon dioxide is the main driver of global warming, understanding how temperature affects this process is crucial for predicting climate change.
It was previously thought that plants lose most of their water through their pores, which close in extreme heat to conserve water. But our research found that as temperatures rise, plants lose more water through their cuticle—the waxy layer on their leaves, which cannot close—than through their pores. The thinner the cuticle, the greater the water loss.
This means that in extreme heat, plants continue losing water but cannot take in carbon dioxide, limiting photosynthesis and reducing their role as a carbon sink. In extreme temperatures, they could even become carbon sources, accelerating climate change.
My back-of-the-envelope calculation suggests that a medium-sized leaf exposed to 50 °C could lose about one-third of a teaspoon of water per day through the cuticle. Scaled up to entire forests, this could alter global water and carbon cycles—an impact that our current climate change models may underestimate.
How hot is too hot?
In another study of 200 plant species in Vancouver, we found that photosynthesis starts to break down between 40 and 51 °C. During the 2021 heat dome, temperatures soared to 49.6 °C, pushing plants to their limits.
Our ongoing research suggests that 60 °C may be the highest temperature plants can survive—beyond this point, proteins break down, leading to cell injury and death. Only a few desert and tropical species have ever been observed surviving at such extreme temperatures.
Globally, researchers are working to determine the “tipping point” where Earth’s vegetation releases more carbon dioxide than it absorbs, switching from a carbon sink to a carbon source. Our estimates suggest this could happen around 30 °C, though key uncertainties remain—especially how microclimates and water availability affect photosynthesis under extreme heat.
With global temperatures already averaging 16°C, understanding these limits is critical for predicting climate feedback loops and the future of Earth’s ecosystems in a warming world.
What can we learn from human-made biospheres?
As a postdoctoral fellow, I worked at Biosphere 2, a research facility originally designed as a self-sustaining, closed ecological system. Researchers, called biospherians, were sealed inside for a planned two-year experiment to test whether humans could survive without external oxygen or supplies. The goal was to test this concept on Earth, with the idea of sending such domes into space someday. However, the experiment faced unexpected challenges: concrete curing led to a carbon dioxide buildup, while prolonged isolation triggered social and psychological stress among the biospherians.
Biosphere 2 later transitioned into a research and public education centre, where I studied how high temperatures affect plants in its experimental rainforest.
Plants have survived climate shifts for hundreds of millions of years, but all species face upper limits set by the laws of physics. While some plants can tolerate higher temperatures better than others, the precise breaking point – and how soon plants might reach it – remains uncertain. But based on recent measurements, we may be closer than we think.
Journal
New Phytologist
