Scientists have warned for years that a warming planet threatens human health. Climate models predict more extreme storms, rising oceans, and worse wildfires. These same models also predict significant changes for plants. A new study says those changes could be much worse than we thought.
The research comes from a team at the University of Arizona. It was published in Nature Communications. The study looked at something called canopy temperature. This is the actual temperature on a plant’s leaves. It’s different from air temperature. And it matters a lot for plant health.
The findings are striking. By the end of this century, leaf temperatures could rise 16% more than the air around them. That’s a big gap. Lead researcher Julia K. Green, a professor at the university, says most climate models don’t account for this. They use air temperature instead. That’s a problem.
“Plant surface temperature has a first-order impact on plant photosynthesis, transpiration, respiration, and other important processes,” Green explained. Most researchers rely on air temperature data. But that approach misses something important. It underestimates how much heat plants actually experience.
This gap matters. It could throw off climate predictions in serious ways. Rising canopy temperatures could hurt biodiversity. They could shift where plants grow. They could even affect weather patterns and speed up climate change itself.
Why Are Leaves Hotter Than the Air?
Air temperature has always been the main focus for climate policies. That makes sense. It’s what affects people most directly. It’s also simpler to measure than land surface temperature, which better shows what plants actually feel.
Canopy temperature is harder to track. Still, Green’s team found a pattern. Leaf temperatures rise faster than air temperatures. Her team calculated the gap at about 0.11 degrees Celsius, or 16%, by century’s end.
Green offers a simple comparison. Picture a hot parking lot in summer. Touch the pavement, and it’s far hotter than the air around it. Leaves work the same way. They absorb direct sunlight. That makes them heat up faster than the surrounding air.
Plants do have a cooling system. It’s called transpiration. On warm days, plants draw water up to their leaves. That water evaporates. This cools the leaf surface down. Think of it like sweating.
But there’s a catch. In extreme heat and dryness, plants lose water faster than they can replace it. When this happens, plants shut down. They stop photosynthesis. They stop transpiration. Without that cooling process, leaves heat up even faster.
Dry, Hot Regions Face the Biggest Risk
The research team wanted to know why this gap between canopy and air temperature was happening. They found a clear link to dry conditions.
Green says the largest increases showed up in places where the air is expected to get drier. As air gets hotter and drier, plants lose more water through transpiration. This forces them to shut down sooner. And that leads to even hotter leaves.
There’s also a feedback loop at play. When plants stop transpiring, less water evaporates into the air. That makes the surrounding air even drier. Drier air then stresses plants further.
Dry regions will likely see the biggest changes. But Green is also concerned about tropical areas. “Tropical plants are less accustomed to large temperature fluctuations, so they aren’t adapted for the increase in temperature,” she said. Even small temperature shifts could seriously disrupt these ecosystems.
Why This Matters for the Whole Planet
This research shows why canopy temperature deserves more attention in climate models. Plants do more than grow. They absorb carbon dioxide. They influence weather. And climate change affects them just as much as they affect it.
Green explains that every plant has an ideal temperature for photosynthesis. Push past that point, and photosynthesis slows down. That means plants absorb less carbon dioxide. More carbon dioxide stays in the atmosphere. And that speeds up warming even further. It could also lead to shifts in where plants grow and even plant die-offs.
There’s another piece to this puzzle. Transpiration doesn’t just cool leaves. It cools the air, too. It also releases water vapor that helps form clouds and rain.
When plants struggle, they transpire less. Less water vapor enters the atmosphere. Rainfall patterns can shift as a result. Cloud cover changes too, and that affects how much sunlight reaches the ground.
Green believes this study will help scientists build better climate models. Models that properly account for canopy temperature will be more useful. They can guide better decisions for both policymakers and the public.
“The more accurate our climate change models are, the more informed our decisions can be,” Green said. Understanding what’s coming, she added, is the first step toward real solutions.
