Scientists have discovered a “hidden order” in the earth’s drylands. There, plants follow a chaotic hyperuniformity. This arrangement appears random and chaotic when viewed up close, but from a distance it follows a clear pattern.
The discovery explains phenomena such as West Africa’s “tiger bush,” where bands of plants look like tiger stripes when viewed from above, and Namibia’s “fairy circles,” which look like patches from a distance but are actually clumps of plants. These plants are self-organized in ways that help them cope with drought and function in extreme conditions.
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In the new study, published Oct. 7 in the journal PNAS, researchers examined satellite images of more than 400 arid regions around the world and mathematically analyzed the spatial patterns of vegetation in those landscapes. They found that while the distribution of plants may appear chaotic on the ground, 10% of dry land follows a super-uniform pattern when viewed from the air. This indicates that this phenomenon is not only rare but also a widespread feature of many arid ecosystems.
This pattern is likely the result of intense competition for scarce resources, Liu said. This ultra-uniform arrangement allows the plants to survive with limited water. This pattern allows for the right balance for arid ecosystems, because if they are too close together, individual plants will compete for water, but if they are too far apart, there will be gaps for other plant types to invade.
Over time, the plant slowly organizes into the chaotic hyper-uniform state formed by this balance. “This is a great new strategy to maximize resource use and minimize competitive conflict across communities,” Liu said.
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Chemists first defined disordered hyperuniformity in the 2000s. They observed atoms that were not arranged in crystalline solid patterns (highly organized grids) or in liquid or gas patterns (significantly less organized and random). Instead, they were arranged in a chaotic and highly uniform manner, giving them the benefits of an organized system, but with greater flexibility.
Scientists are increasingly identifying this pattern throughout nature, from the atomic scale to entire galaxies. The rods and cones of a bird’s eye are organized in a very uniform way, and some algae swim in very uniform patterns.
According to Zhao’s research, this has been observed before in plants, such as leaf vein networks.
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“We can learn a lot from these biological systems that have been optimized by years of evolution and natural selection,” Yan Zhao, an engineer at Arizona State University who was not involved in the study, told Live Science. “We are not surprised by this result; similar to what we showed with the leaf pattern, when the environment is harsh, the system adapts better toward an optimal hyperuniform state,” he added.
However, this optimal balance makes it difficult for ecosystems to recover from human disturbances such as climate change, invasive species, and infrastructure.
“Roads and ditches act as scars that block water flow,” Liu said. “Once those gradients are disturbed, the ‘hidden order’ collapses. In this way, loss of hyperuniformity can serve as a sensitive early warning sign that the ecosystem is under stress and losing the natural resilience provided by this hidden order.”
Liu’s team now plans to explore hidden order in other extreme ecosystems, including beyond Earth. Analysis of images of Martian craters taken by NASA’s Curiosity rover shows that the clumps of pebbles on the sand exhibit the same chaotic hyperuniformity as dryland plants on Earth, driven not by biology but by physical forces such as wind, sand movement, and gravity.
“That the same geometric principle appears in such different systems suggests that disordered hyperuniformity is a universal solution to the challenge of packing and efficiency under constraints, whether the ‘particles’ are plants, pebbles, or cells,” Liu said.
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