Tropical Rainforests at Risk of More Human-Created Nitrogen Pollution Than Previously Thought

It turns out that we have far more of an effect on nitrogen levels in the tropics than we might have expected. Scientists have discovered that humans have more than doubled tropical nitrogen inputs due to pollution and other sources.

Nitrogen is an essential nutrient for both plant and animal life. It's required to form many basic molecules, and can enter the environment either through a microbial process called biological nitrogen fixation, or through human activity. When it comes to human activity, the nitrogen can enter ecosystems through fertilization and fossil-fuel consumption among other sources of pollution.

It's these sources of pollution that can cause issues for the environment, though. Too much nitrogen can lead to dead zones in the ocean, and can pollute both air and drinking water. It can also contribute to a number of human illnesses.

In order to learn a bit more about nitrogen in the tropics, the researchers examined the nitrogen cycle in tropical rainforests. More specifically, they employed a new method to demonstrate that biological nitrogen fixation in these forests may be less than a quarter of previous estimates.

"This research fundamentally changes our understanding of the tropical nitrogen cycle," said Benjamin Sullivan, one of the researchers, in a news release. "It shows that few ecosystems on Earth have escaped the impact of human activity."

The findings are especially important when examining how nitrogen impacts these tropical rainforests. In the past, scientists assumed that rainforests had high levels of nitrogen fixation and that humans added relatively little nitrogen to these tropical ecosystems. It turns out, though, that this isn't the case.

The scientists stress the importance of taking steps to help mitigate nitrogen pollution. Preserving human and ecosystem health requires immediate action to solve the growing problem.

The findings are published in the journal Proceedings of the National Academy of Sciences.