Why Soil’s Declining Nitrogen Levels Could Threaten Our Climate: Understanding the Impact and Solutions

Plants rely on nitrogen in the soil to absorb carbon from the air. A recent global study reveals that forests and other natural areas are getting less nitrogen than scientists thought. This shortage might hinder nature’s role in fighting climate change.

On the other hand, farms worldwide are using more nitrogen to help crops grow. However, excess nitrogen can contaminate water, air, and harm biodiversity.

Carla Reis Ely led the research while at Oregon State University, with a team of 24 scientists from various countries. They looked at data on biological nitrogen fixation, the process where certain microbes convert atmospheric nitrogen to forms that plants can use. Previous studies mainly focused on regions rich in nitrogen-fixing organisms, which skewed earlier estimates of nitrogen availability. By correcting this bias, the new study shows that natural nitrogen inputs are lower than previously believed.

Nitrogen is abundant in the atmosphere, yet most organisms cannot directly use it in its gaseous form. Nitrogen-fixing bacteria play a crucial role by converting it into ammonia, a form plants can absorb through their roots. Nitrogen is essential for plants to grow, reproduce, and produce the chlorophyll that drives photosynthesis. According to Reis Ely, nitrogen fixation boosts soil fertility and enhances carbon capture in natural ecosystems.

If natural landscapes are receiving less nitrogen, plants may struggle more than expected. This could lead to slower growth and a reduced ability to capture CO₂, complicating global climate models which already estimate lower carbon capture capabilities from unmanaged lands.

A striking contrast exists in agriculture. Farmers increasingly utilize nitrogen-fixing crops like legumes, which naturally enrich the soil. While this method reduces the need for synthetic fertilizers and supports higher yields, it’s vital to maintain balance. Too much nitrogen in soil can disrupt nutrient levels and lead to water contamination or promote harmful algae blooms that affect aquatic ecosystems.

Excess nitrogen can also turn into nitrous oxide, a potent greenhouse gas, altering plant communities and potentially harming native species. Reis Ely remarked, “High agricultural nitrogen fixation is beneficial, but it also contributes to nitrogen pollution and climate change.” Continuous monitoring of nitrogen fixation processes is crucial for maintaining equilibrium.

The implications of the study extend beyond theoretical knowledge. Governments and organizations are counting on land-based carbon capture strategies, such as reforestation and soil carbon programs, to meet climate goals. If the nitrogen limitations are tighter than assumed, these projected carbon gains may need adjustments. Policies on nutrient management and water quality also depend on precise data about nitrogen levels.

Moving forward, using nitrogen-fixing crops smartly is essential. Better crop management and reducing food waste can minimize nitrogen loss while still supporting food needs. The key will be tracking biological nitrogen fixation to keep the nitrogen balance in check.

In summary, while nature’s nitrogen supply might be declining, our agricultural systems have a wealth of it. Striking a balance between these systems will be key in protecting our environment while ensuring food security.

This study is published in the journal Nature.

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