Earth Can Support More Plant Growth Than Previously Thought: Agriculture Boosts Productivity

It turns out that our planet may not be as green as it could be. Scientists have found that Earth can produce much more land-plant biomass than previously thought.

In the past, scientists have used estimates from satellite images of vegetation and modeling in order to find out how much plant biomass our planet could support. These past estimates have suggested that about 54 gigatons of carbon is converted into terrestrial plant biomass each year. This particular value has remained stable for the past several decades, which has led some scientists to believe that it represents an upper limit of global biomass production.

Yet this may not be the case. In fact, the answer is far too simple. Scientists have failed to take human efforts into consideration.

"When you try to estimate something over the whole planet, you have to make some simplifying assumptions," said Evan DeLucia, one of the researchers, in a news release. "And most previous research assumes that the maximum productivity that you could get out of a landscape is what the natural ecosystem would have produced. But it turns out that in nature very few plants have evolved to maximize their growth rates."

In this case, the researchers used a model of light-use efficiency and the theoretical maximum efficiency with which plant canopies convert solar radiation to biomass. This allowed them to estimate the theoretical limit of net primary production (NPP) on a global scale. They found that, surprisingly, the new calculated limit was two orders of magnitude higher than previous estimates.

So why the much higher limit? Previous studies failed to take into account human efforts to boost plant productivity through genetic manipulation, plant breeding and land management. These efforts have created some extremely productive plants.

"I don't want to be the guy that says science is going to save the planet and we shouldn't worry about the environmental consequences of agriculture, we shouldn't worry about runaway population growth," said DeLucia. "All I'm saying is that we're underestimating the productive capacity of plants in managed ecosystems."

The findings are published in the journal Environmental Science & Technology.