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Don't be afraid of environmental tipping points.  Because they are often not there.

Don’t be afraid of environmental tipping points. Because they are often not there.

Ice cap melting due to global warming. When they melt, less sunlight is reflected, causing the Earth to warm and more ice to melt. Scientists warn that we are approaching a tipping point. The ice quickly melts too quickly for the winter buildup to handle.

Turning points in fashion. They are currently attracting the most interest in climate and environmental sciences. Savannas turn into deserts, permafrost thaws and releases greenhouse gases, and lakes are flooded with pollution. They will all follow the logic of the tipping point: a self-reinforcing effect that causes the system to shift into a new state, from which it is then difficult to get out. Scientists see some changes as a warning sign that a tipping point is approaching, such as dry patches in the savannah or tangles of algae in the sea.

But Max Ritkirk, a professor of spatial ecology at Utrecht University, differentiates nuisances about tipping points. “The spatial patterns – such as dry patches or tangles of algae – that can arise in disturbed ecosystems do not have to be a sign of a dramatic tipping point. They can themselves form a new, resilient and stable system.” A research group led by Rietkerk and Leiden mathematics professor Arjen Doelman has published a report on the subject Scientific article in early October in a Science. “Complex systems such as ecosystems and climate can avoid tipping points.”

Are there no turning points?

“There are tipping points, such as when small and shallow lakes become turbid, but in large systems, true tipping points are rarely seen. There are many scientific articles that warn that systems are approaching a point of no return, but essentially describe the changes, which does not mean You’re moving toward a tipping point.In the sea, for example, you can see that there can be local algae growth, without the entire sea becoming cloudy.

“For a long time I was also thinking in terms of tipping points, like that the savannah was a tipping point in the Sahara. But the only example of that is the widespread desertification in the Sahel, in Africa, in the 1970s due to drought and overgrazing. But now we see it’s less arid there. The system appears to be recovering on its own. This does not mean we can rule out climatic tipping points or large ecosystems, but it does seem unlikely.”

A savannah with a little green doesn’t necessarily turn into a desert

How did your new view on critical points emerge?

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“I owe it to the mathematicians. I worked on models depicting a tipping point from the savannah to the desert due to reduced vegetation – for example, through overgrazing. Vegetation ensures the soil’s ability to hold water better. Less vegetation means less water In the soil, so that more vegetation disappears until you have a desert. At that time I met a mathematician who advised me not to look at a small homogeneous area, but at a larger area in a spatial context. When I did this with his help, I saw no turning point. It turned out that savannah plants It organizes itself in regular patterns on a larger scale.These can be stripes, like a leopard’s fur, but it can also be spots, like a leopard.

“At first I thought these patterns were harbingers of a turning point. But over time, mathematics has evolved further, and thanks to collaboration between ecologists and mathematicians, we can also look at the stability of those spatial patterns. It turns out that they are more stable than we thought. This means that A savannah with a number of green tufts does not necessarily turn into a desert, but in itself it can be very stable. The pattern can also reorganize and reorganize itself; one tuft less or more does not cause change.”

A fully vegetated area will not work. It is better to plant green tufts

Can spatial patterns from your models also be seen in real life?

About twenty years ago we first saw these spatial patterns on a computer screen. We only knew it actually existed when I showed the simulation to an American colleague. Max, he said, these patterns exist in real life, and I opened a drawer with aerial photos of ecosystems with such patterns. He kept it in a drawer because he couldn’t explain the patterns with the existing ones. Styles are found to fit one-to-one with our model.

In 2018, we conducted a more comprehensive research using satellite images of the arid regions of Somalia over a period of 30 years. Here too we found what our models predict: different vegetation patterns can arise under the same conditions because there are many stable equilibriums. As we have seen, the patterns remain stable despite environmental changes. Then I realized Turning Points is a more accurate story than I thought. It was a turning point in my thinking about turning points.”

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Can we do something with knowledge about stable spatial patterns?

“You can help them by giving them space and preventing changes from happening too quickly, for example by preventing overgrazing. Additionally, you can use spatial patterns to restore vegetation in an arid area. A fully vegetated area will not work. It is better to plant Wisps of green space to bring about natural spatial processes.That’s why I think the 8000 km Great Green Wall to be built in the Sahel and the Sahara is a strange idea.

“In Burkina Faso in West Africa, I saw local knowledge about following spatial patterns. For example, they build stone dams along natural bare cliffs to collect water from the area of ​​bare cliffs above. As a result, plants begin to grow behind those dams. There is no Enough water to make everything green, but if you collect water and concentrate the greenery there, there is more than enough.”

The fact that we see these spatial patterns still means that something is going on

Does this mean you don’t have to worry about tipping points?

“The fact that we see these spatial patterns still means that something is happening. It’s good not to assume that the system has a tipping point. But now we need to examine the conditions in which tipping points do or don’t happen. I think you can cross out at least 50 in 100 predicted tipping points. Like predictions about global tipping points that could lead to the Earth’s greenhouse. I don’t think these global tipping points happen. But locally, climate change can cause serious problems, such as floods, hurricanes and heat waves. It’s good to Dramatic tipping points occur less frequently than we thought, but climate change remains a serious issue, as is also evident from the latest IPCC report from the United Nations Climate Panel.”