Glaciers are melting due to global warming. As they melt, they reflect less sunlight, which warms the earth and melts more ice. We are approaching a critical juncture, scientists warn. Soon the ice will melt very quickly, so the build-up in the winter can no longer withstand it.
Tipping points are in fashion. They are currently attracting more attention in meteorology and ecology. The savannahs turn into deserts, and the permafrost melts and the greenhouse gases and lakes are covered by pollution. They all follow the logic of the tipping point: a self-strengthening effect that causes a system to turn into a new state, from which it is very difficult to get out. Scientists see some changes as an alarm signal that a tipping point is approaching, such as dry spots in the savannah or contractions of sea algae.
But Max Rietkerk, a professor of spatial ecology at the University of Utrecht, is wary of alarmist voices about tipping points. “Spatial patterns – patches of dry patches or algae – that occur in turbulent habitats do not have to be a sign of a dramatic tipping point. They can form a new, more resistant and stable system. A scientific article in early October In Science. “Complex systems such as habitats and climates can avoid tipping points.”
No tipping points?
“There are tipping points where small and shallow lakes are disturbed, but real tipping points are rarely seen on larger systems. Without full cloud cover, you can see local algae growing.
“For a long time, I also thought about tipping points, and the Savannah was a tipping point to the desert. The only example of this is the large-scale desertification of the Sahel in Africa in the 1970s due to drought and overgrazing. But now we see that there is less dryness. The system seems to recover automatically. This does not mean that we can rule out climate tipping points or large habitats, but they do seem unlikely.
It may not turn into a savannah desert with a little greenery
How did your new perspective on tipping points come about?
“I owe it to the mathematicians to work on models that depict a tipping point from the savannah to the desert because the vegetation is shrinking – for example, by ensuring that the soil retains water well. I met a mathematician, who advised me not to look at a small homogeneous area, but in a spatial context over a large area, and when I did it with his help, I found no tipping point, realizing that the savanna vegetation was largely organized in regular patterns, which could be tiger-like stripes, like leopard-like stripes. .
“At first I thought those patterns were the beginning of a tipping point, but over time, as mathematics developed, thanks to the collaboration between ecologists and mathematicians, we could see the stability of those spatial patterns. It’s very sustainable, the pattern can reorganize and reorganize itself; it will not change more or less. ”
An area completely covered with vegetation will not work. It is best if you plant green plants
Can you see the spatial patterns from your models in real life?
“We first saw these spatial patterns on this computer screen about twenty years ago, and only when I showed the simulations to an American colleague did we know that they actually exist,” he said: “Max, those patterns exist in real life. He kept it in his drawer as he could not explain the patterns using and found the patterns to fit one by one with our model.
In 2018, we conducted more extensive research using satellite imagery of arid regions in Somalia over a period of 30 years. Here again we found our models predictable: many flora may emerge in the same state because there are several stable equilibria. We also saw that patterns remain stable despite environmental changes. I realized that the tipping points were a more subtle story than I thought. It was a turning point in my thinking about tipping points. ”
Is there anything we can do with knowledge of sustainable spatial patterns?
“You can give them a hand by giving them space and preventing changes from happening too quickly, for example by preventing excessive grazing. Also, you can use spatial patterns to restore plants to a barren area. I think the 8,000km long green wall plants being built in the Sahara are a weird idea.
“In Burkina Faso, West Africa, I found local knowledge of following spatial patterns. For example, they make stone pits on natural slopes to collect water from the upper bare slopes. As a result, plants begin to grow behind those pits. There is more than enough. ”
The fact that we still see those spatial patterns means that something is going on
Does this mean we should not worry about tipping points?
“The fact that we see those spatial patterns means that something is still going on. It is a good idea to think of a priori as a system that has a tipping point. But we now need to examine under what circumstances tipping points may or may not occur. I think you can write off at least 50 percent of the predicted tipping points. Such as predictions of global tipping points that could lead to a hothouse land. I don’t think those global tipping points are happening. But locally, climate change can cause serious problems such as floods, hurricanes and heat waves. The good news is that dramatic tipping points are lower than we thought, but climate change remains a serious issue, as evidenced by the latest IPCC report from the UN Climate Panel.
A version of this article also appeared in the NRC on the morning of October 25, 2021
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