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After hundreds of years of stability prior to the industrial revolution, new research shows that plant photosynthesis grew rapidly in the 20th century.

A team led by UC Merced researchers have discovered a chemical record of global photosynthesis spanning hundreds of years, and estimated that the sum of all plant photosynthesis on Earth grew by 30 percent over the 200-year record they captured.

“Virtually all life on our planet depends on photosynthesis,” UC Merced Professor Elliott Campbell, who led the research, said in a statement. “Keeping tabs on global plant growth should be a central goal for the human race.

“Previous studies covered small physical areas or short periods of time,” he added. “We set out to find a long-term record for the whole planet.”

The researchers discovered the record of global photosynthesis by analyzing Antarctic snow data captured by the National Oceanic and Atmospheric Administration.

Gases trapped in different layers of Antarctic snow allow scientists to study global atmospheres of the past, but the key was finding a gas stored in the ice that provided a record of the Earth’s plant growth. Previous studies have found that carbonyl sulfide (COS) serves this function.

Photosynthesis is the process through which plants use sunlight to convert carbon dioxide into carbohydrates to fuel their growth and other activities.

However, researchers lack a clear picture of global trends in photosynthesis over the past few centuries. While some human activities might have stimulated plant growth, others might have hampered photosynthesis.

Scientists have debated for years the conflicting results from different experiments regarding photosynthesis.

 “Studies have already demonstrated unprecedented changes in climate and greenhouse gases during the industrial era,” Campbell said. “Now we have evidence that there is also a fundamental shift in the Earth's plants.”

While the research did not identify the cause of the increased photosynthesis, computer models have shown several processes that could together create such a large change in global plant growth.

The leading candidates are rising atmospheric CO₂ levels, a result of emissions human activities, as well as longer growing seasons, a result of climate change caused by CO₂ emissions and nitrogen pollution, another result of fossil fuel combustion and agriculture.

“The rising CO₂ level stimulates crops yields,” Campbell, who’s with the School of Engineering Opens a New Window. and the Sierra Nevada Research Institute, saidOpens a New Window. . “But it also benefits weeds and invasive species.

“Most importantly, CO₂ emissions cause climate change, which will increase flooding of coastal cities, extreme weather and ocean acidification.”

The rise in photosynthesis also can cause plants to remove CO₂ from the air and store it in ecosystem, however CO₂ emissions from fossil fuel burning overwhelm any uptake by plants.

“The increase in photosynthesis has not been large enough to compensate for the burning of fossil fuels,” paper co-author Joe Berry, from the Carnegie Institution for Science, said in a statement. “Nature’s brakes have already been overwhelmed.

“So now it’s up to us to figure out how to reduce the CO₂ concentration in the atmosphere.”

The research team plans to continue to study current changes in photosynthesis using the ongoing COS measurements made by NOAA.

“Part of predicting the future state of our atmosphere depends on understanding natural mechanisms and how they are changing over time,” Steve Montzka, a research chemist with NOAA, said in a statement. “We are making measurements and observations and if we don’t continue to do that, we won’t have the fundamental information needed to answer important questions related to future atmospheric changes.”

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