How do humans affect the nitrogen cycle?

One of the most important elements for life on Earth, nitrogen makes up 78 per cent of the air we breathe and provides vital nourishment for plants to grow. However, modern life is causing catastrophic changes to the delicate balance that has kept our planet’s ecosystems thriving for millennia. As the nitrogen cycle is disrupted, it has knock-on effects across the planet.

Despite this, there are a number of ways we can restore the nitrogen cycle and avert an environmental crisis. But to do that, first we must understand how human actions affect it, and why they are harming our planet.

Ocean dead zones

Rain can wash nitrates into watercourses and oceans. This nitrogen-based pollution feeds algal blooms that suck up oxygen as they decompose, choking aquatic life. The result is a watery “dead zone”, of which there are more than 400 in the world’s oceans, including a huge one in the Gulf of Mexico.

Air pollution

Cars and power plants emit nitrogen oxides, which are one of the principal precursors to a type of air pollution called particulate matter. These tiny particles can be breathed into our lungs, where they cause tissue damage associated with a range of health problems.

Soil acidification

The same nitrate that can sneak into waterways can also pull key nutrients out of the soil, including magnesium and calcium. This can make soil too acidic, such that plants are unable to take up nutrients properly.

Ozone depletion

Rising levels of ammonia pollution are decreasing the acidity of the air. Certain habitats, such as peat bogs, rely on the air being slightly acidic. In Northern Ireland, this problem is causing the degradation of sphagnum peat moss bogs, a major store of carbon dioxide.

Alkaline air

Excess nitrate can be converted by bacteria into nitrous oxide gas. At high altitudes, this reacts with ultraviolet light and eats away at the ozone layer that shields us from UV rays. The damage is tough to undo because nitrous oxide has a lifespan of 120 years.