How Biogeochemical Factors Affect Environmental Health and Climate Change

Every breath you take, every meal you eat, and every drop of water you drink depends on the continuous movement of chemical elements through Earth’s systems. Carbon, nitrogen, and phosphorus cycle between the atmosphere, water, soil, and living organisms in processes known as biogeochemical cycles. These cycles have sustained life for billions of years. But human activities – from burning fossil fuels to intensive farming – are now disrupting these natural processes at an alarming rate, with direct consequences for environmental health and climate change.

What are biogeochemical cycles? 🔗

Biogeochemical cycles describe how essential elements move between different environmental compartments: the atmosphere, hydrosphere (water), lithosphere (rocks and soil), and biosphere (living organisms). The term itself breaks down into three parts – “bio” for biological processes, “geo” for geological systems, and “chemical” for the elements involved. These cycles ensure that nutrients are continuously recycled, making them available for plants, animals, and microorganisms to use again and again.

The three most critical biogeochemical cycles for environmental health are the carbon cycle, the nitrogen cycle, and the phosphorus cycle. Each operates through distinct pathways, but they are deeply interconnected. When one cycle is disrupted, the effects cascade across the others. For example, disruptions caused by industrial agriculture, deforestation, and pollution affect multiple cycles simultaneously, threatening ecosystem stability and human wellbeing.

How human activities have accelerated biogeochemical cycles 🔗

For most of Earth’s history, biogeochemical cycles operated in a relatively stable equilibrium. Natural processes like volcanic eruptions, weathering of rocks, and biological decay moved elements slowly between reservoirs. Human activities have fundamentally changed both the speed and scale of these movements.

Fossil fuel combustion 🔗

Burning coal, oil, and natural gas releases carbon that was stored underground for millions of years. According to NOAA, human activities have significantly increased the amount of carbon dioxide in the atmosphere, which is now greater than at any point in at least 3.6 million years. Additionally, fossil fuel combustion releases nitrogen oxides into the atmosphere, adding to reactive nitrogen levels well beyond what agricultural sources alone contribute.

Intensive agriculture 🔗

Modern farming relies heavily on synthetic fertilizers to boost crop yields. However, a large portion of the nitrogen and phosphorus applied to fields is not absorbed by crops. These excess nutrients leach into waterways and the atmosphere, disrupting natural nutrient cycles. According to research published in PNAS, between 1950 and 2000, the global nitrogen surplus rose to 138 teragrams per year, while the phosphorus surplus reached 11 teragrams per year.

Deforestation and land-use change 🔗

Clearing forests for agriculture or urban development reduces the planet’s capacity to absorb carbon dioxide through photosynthesis. Trees are major carbon storage systems, and their removal not only releases stored carbon but also limits future carbon sequestration. Urban development further compounds the problem by replacing natural landscapes with impermeable surfaces that prevent nutrient recycling in soils.

The carbon cycle and climate change 🔗

The carbon cycle is at the centre of the climate change discussion. Carbon moves naturally between the atmosphere, oceans, plants, soil, and rocks. When this cycle is balanced, the amount of carbon released roughly equals the amount absorbed. Human activity has thrown this balance off.

Fossil fuels and excess atmospheric carbon 🔗

When fossil fuels are burned, they release carbon dioxide – a potent greenhouse gas that traps heat in the atmosphere. As NASA reports, CO₂ emissions from fossil fuels reached 36.8 billion metric tons in 2023, a 1.1% increase over 2022. This continuous rise makes it increasingly difficult to limit global warming.

The NOAA Global Monitoring Laboratory notes that carbon dioxide is responsible for approximately 80% of the total heating influence of all human-produced greenhouse gases since 1990. The annual rate of CO₂ increase over the past 60 years has been 100 to 200 times faster than the increase that occurred at the end of the last ice age.

Feedback loops that worsen warming 🔗

The carbon cycle contains several positive feedback loops that amplify climate change. As global temperatures rise, permafrost – soil that remains frozen year-round – begins to thaw. This releases methane, another greenhouse gas, which further accelerates warming. Rising ocean temperatures reduce the ocean’s capacity to absorb CO₂, meaning more carbon stays in the atmosphere. Meanwhile, natural carbon sinks like forests and oceans, which currently absorb about half of human-emitted CO₂, may become less effective as conditions change.

Ocean acidification 🔗

Excess atmospheric CO₂ doesn’t just warm the planet – a significant portion dissolves into the ocean. This lowers the ocean’s pH, a process called ocean acidification. Acidification interferes with the ability of marine organisms like corals, crabs, and shellfish to build their shells and skeletons, threatening marine food chains and the communities that depend on them.

The nitrogen cycle: from fertilizer fields to greenhouse gases 🔗

Nitrogen is essential for all living organisms – it’s a key building block of proteins and DNA. About 78% of Earth’s atmosphere is nitrogen gas (N₂), but this form is unreactive and unavailable to most organisms. Naturally, nitrogen is converted into usable (“reactive”) forms by lightning and nitrogen-fixing bacteria in soil.

The Haber-Bosch revolution and its consequences 🔗

The invention of the Haber-Bosch process in the early 20th century transformed agriculture by enabling industrial-scale production of ammonia from atmospheric nitrogen. This breakthrough helped feed a growing global population. However, it also meant that human activities now produce more reactive nitrogen than all natural sources combined. According to the Planetary Health Check, anthropogenic nitrogen fixation has increased from zero to approximately 190 teragrams per year globally – far exceeding the planetary boundary of 62 teragrams per year.

Nitrogen pollution and its cascading effects 🔗

Excess reactive nitrogen moves through the environment in what scientists call the “nitrogen cascade” – a single nitrogen atom can trigger a sequence of environmental problems as it moves through air, water, and soil. The consequences include:

Air quality degradation: Reactive nitrogen compounds like ammonia and nitrogen oxides contribute to smog, fine particulate matter (PM 2.5), and ground-level ozone, all of which compromise human health through increased respiratory problems.

Water contamination: Nitrates leaching into groundwater compromise drinking water safety. Surface water eutrophication – where excess nutrients cause explosive algal growth – depletes oxygen and creates dead zones where aquatic life cannot survive.

Greenhouse gas emissions: Nitrous oxide (N₂O), released from agricultural soils treated with nitrogen fertilizers, is a potent greenhouse gas approximately 300 times more effective at trapping heat than CO₂ over a 100-year period. It also contributes to stratospheric ozone depletion.

The phosphorus cycle: a finite resource under pressure 🔗

Unlike carbon and nitrogen, phosphorus does not have a significant atmospheric phase. It cycles primarily through rocks, soil, water, and organisms. Phosphorus is released naturally through the slow weathering of rocks, making its natural cycling rate extremely slow compared to carbon and nitrogen.

Human disruption of phosphorus flows 🔗

Research published in Environmental Science & Technology shows that human activities have tripled global phosphorus mobilisation in the land-water continuum. The primary drivers are phosphate rock mining for fertilizer production, agricultural application, and waste generation. Approximately 30% of atmospheric phosphorus transfer is now caused by human activities.

Eutrophication: the most visible impact 🔗

When excess phosphorus (and nitrogen) from agricultural runoff enters lakes, rivers, and coastal waters, it triggers eutrophication. Algae bloom rapidly, and when they die and decompose, the process consumes dissolved oxygen in the water. This creates hypoxic or “dead” zones where fish and other marine life cannot survive. The number of coastal dead zones has grown from nine in the 1960s to over 460, a dramatic indicator of how severely nutrient cycles have been disrupted.

Phosphorus scarcity: a looming crisis 🔗

Phosphorus is a non-renewable resource. Unlike nitrogen, which can be synthesised from atmospheric gases, phosphorus must be mined from phosphate rock deposits. As these deposits are depleted and global food demand continues to rise, securing a sustainable phosphorus supply is becoming a serious food security concern – especially since much of the mined phosphorus is lost to waterways rather than effectively recycled.

The interconnection between cycles and environmental health 🔗

One of the most important aspects of biogeochemical disruption is that the three cycles do not operate in isolation. Changes in one inevitably affect the others. Excess phosphorus in ecosystems can stimulate carbon and nitrogen cycling, which in turn affects greenhouse gas emissions. Higher atmospheric CO₂ levels alter plant growth patterns, which changes how much nitrogen plants absorb from soils.

These interconnections mean that the environmental and health consequences multiply. The Planetary Health Alliance notes that nutrient overloading decreases the nutritional quality of crops, contributes to the spread of disease vectors like malaria, and degrades both drinking water and marine ecosystems that humans depend on for food.

Direct impacts on human health 🔗

The health consequences of disrupted biogeochemical cycles are wide-ranging. Nitrate-contaminated drinking water poses risks of methemoglobinemia (blue baby syndrome) and has been linked to certain cancers. Harmful algal blooms produce toxins that can contaminate drinking water supplies and bioaccumulate through food chains. Air pollution from reactive nitrogen worsens asthma, cardiovascular disease, and other respiratory conditions. Additionally, elevated CO₂ levels have been shown to reduce the protein and mineral content of staple crops like wheat and rice, contributing to nutritional deficiencies in populations that depend on them.

What can be done? 🔗

Addressing disrupted biogeochemical cycles requires action across multiple fronts. Precision agriculture – using technology to apply fertilizers more efficiently – can significantly reduce nitrogen and phosphorus runoff. Improved wastewater treatment and nutrient recycling from livestock manure and human waste can help return valuable nutrients to productive use rather than losing them to the environment.

On the carbon side, transitioning away from fossil fuels toward renewable energy sources is essential for reducing CO₂ emissions. Protecting and restoring forests, wetlands, and other natural carbon sinks boosts the planet’s capacity to absorb excess carbon. Integrated environmental policy is equally important – climate policies must consider nitrogen and phosphorus cycles, and agricultural policies must account for greenhouse gas emissions.

The scientific community increasingly emphasises that addressing these interlinked threats demands not just limiting excess nutrient flows but also investing in early detection, monitoring, and regulation. Interdisciplinary research is urgently needed to define safe thresholds and understand how these stressors interact under accelerating climate change.

What do you think? Given that the carbon, nitrogen, and phosphorus cycles are so deeply interconnected, can we effectively address climate change without simultaneously tackling nutrient pollution – and how might changes in your daily food choices contribute to restoring balance in these cycles?

References

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC12025154/
2. https://www.noaa.gov/education/resource-collections/climate/carbon-cycle
3. https://pmc.ncbi.nlm.nih.gov/articles/PMC3876211/
4. https://earthobservatory.nasa.gov/images/152519/emissions-from-fossil-fuels-continue-to-rise
5. https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide
6. https://www.planetaryhealthcheck.org/boundary/modification-of-biogeochemical-flows/
7. https://pmc.ncbi.nlm.nih.gov/articles/PMC7982378/
8. https://pubs.acs.org/doi/10.1021/acs.est.7b03910
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC3682738/
10. https://planetaryhealthalliance.org/themes/nutrient-overloading-and-cycling/
11. https://www.frontiersin.org/journals/environmental-science/articles/10.3389/fenvs.2025.1643879/full