Nature’s grip on CO2 is slipping: What it means for us all

Climate change has long been framed as a battle between what humans emit and what nature can absorb. At the heart of this balance lies carbon sequestration – the process where plants, trees, and soils pull carbon dioxide (CO2) from the atmosphere and store it.

For decades, this natural mechanism offered a quiet form of resistance against rising emissions. But now, researchers have uncovered a troubling shift: the Earth’s ability to absorb CO2 is weakening.

A new study by the University of Strathclyde suggests that the safety net we once relied upon is beginning to fray. As sequestration declines, the race to cut emissions becomes even more urgent.

While the planet continues to green in appearance, the inner mechanisms that drive long-term carbon storage may be breaking down. The implications stretch far beyond science – they strike at the heart of climate policy, land use, and our collective future.

Nature is storing less CO2 each year

The study reveals that natural sequestration once kept pace with growing emissions. In the 1960s, carbon sequestration grew by 0.8% annually.

This increase suggested that as human activity released more CO2, plants and forests were also working harder to absorb it. That gave many scientists and policymakers hope that natural systems could buy time as humanity worked on long-term solutions.

But that growth didn’t last. The research found that the sequestration rate peaked in 2008 and is now in decline – falling by 0.25% per year. The numbers show a concerning reversal.

If the 1960s growth had continued uninterrupted, natural carbon uptake would have increased by 50% between 1960 and 2010. Instead, if the current downward trend continues, nature’s ability to absorb CO2 could drop by half over the next 250 years.

The study, published in the journal Weather, offers a stark warning. As emissions rise and sequestration shrinks, the margin for error disappears. Carbon is staying in the atmosphere longer, intensifying the warming effect and weakening our natural climate buffer.

Human emissions keep climbing

While nature’s absorption rate drops, human-generated emissions continue to climb. The report states that emissions from human activities are growing at a rate of about 1.2% annually. That figure may seem modest, but when matched against a declining carbon sink, it becomes overwhelming.

To cancel out this increase, emissions would need to fall by at least 0.3% per year. That translates to about 100 million tons of CO2 annually.

Achieving such a reduction would require global shifts in energy, transportation, agriculture, and consumption. It’s a monumental task – made harder by the realization that natural systems are no longer absorbing carbon at past levels.

The findings raise difficult questions about how much longer we can lean on forests and soil to balance our carbon books.

For decades, policies around reforestation and conservation hinged on the assumption that sequestration would continue to improve. This assumption may no longer hold true.

Nature’s CO2 rhythm isn’t enough anymore

James Curran, a visiting professor at Strathclyde’s Centre for Sustainable Development, co-authored the study with Dr. Sam Curran. He explained how the Earth’s seasonal rhythms once helped maintain a carbon balance.

“Most of the Earth’s land mass is in the Northern Hemisphere,” said Professor Curran. “During the northern summer, the abundant vegetation of the north absorbs a huge amount of CO2 from the atmosphere.

“In the northern winter, some of this CO2 is released back into the atmosphere through the natural biodegradation of dead vegetation, but a portion remains locked in roots, soil and dormant woody matter. The overall curve of CO2 concentrations still rises year-on-year, owing to additional emissions from human activity.”

This process, known as the seasonal carbon cycle, is visible in atmospheric CO2 data. Every year, levels dip in the summer and rise in the winter. But the long-term trend remains upward. The Earth’s vegetative cover can no longer absorb enough to offset what humans emit.

Biodiversity loss weakens Earth’s defense

Professor Curran emphasizes that restoring nature’s ability to trap carbon is still possible – but time is running out. Reversing the decline in sequestration will require deep investment in ecosystems. That means rethinking how we treat forests, wetlands, grasslands, and even agricultural land.

“It’s urgent that every effort is made to rebuild biodiversity and associated ecosystem services, including sequestration. Deforestation must stop; rewilding must be encouraged; forest fires must be prevented,” said Professor Curran.

”For large-scale habitats, which are more resilient and offer enhanced ecosystem services, defragmentation must be prioritized; fossil fuels must be phased out; timber and fiber products must be reused for as long as possible, as part of a wider circular economy.”

These actions are not optional. They are necessary if we want nature to continue helping us in the fight against global warming. Yet restoring biodiversity is not just about planting trees. It involves protecting complex systems that depend on balance – between species, water cycles, soil health, and climate.

Greener nature doesn’t mean more CO2 absorption

There is a common belief that as CO2 levels rise, so does plant growth. Higher CO2 can act like a fertilizer, making plants grow faster.

This “greening” has been observed in satellite imagery, especially across cold northern regions like Canada and Russia. But this image of a greener Earth may be misleading.

“There was a widespread belief that sequestration was still increasing but would begin to decline at some point in the future, whereas data showed the fall was already underway,” said Professor Curran.

The assumption that more vegetation means better CO2 absorption is now in doubt. Plants may grow faster in warmer, CO2-rich conditions, but other pressures cancel out the gains.

A web of threats to vegetation

Curran explained why increased plant growth doesn’t guarantee more sequestration.

“It is known that increasing CO2 in the atmosphere acts like a plant fertilizer, while a warming world also allows vegetation to grow more rapidly and easily, particularly in the extensive chilly northern latitudes of Canada and Russia.

“Satellite observations are reported as seeing the Earth becoming ‘greener’ as vegetation spreads. However, that simple assumption is countered by all the other effects that can kick in, including damage to vegetative growth by excessive heat, drought, floods, wind damage, wildfires, desertification and potentially wider spread of plant pests and diseases.”

These threats create a volatile and uncertain future for ecosystems. Heat waves and wildfires can destroy decades of growth in a matter of days.

Drought can halt photosynthesis, stopping carbon absorption. Pests and diseases, spread by warming temperatures, can decimate entire regions of plant life.

Nature can still absorb CO2

As the Earth’s capacity to absorb CO2 weakens, the pressure on human systems increases. Emissions must fall faster. Renewable energy must scale quicker.

Land use must prioritize restoration, not destruction. Circular economies – where materials are reused and waste is minimized – must become the norm.

The study from the University of Strathclyde doesn’t just outline a problem. It offers a wake-up call. Nature, once our quiet climate ally, is losing strength. If we want to regain control, we must support ecosystems not just as scenery, but as active partners in climate stability.

Nature is still fighting. But without urgent human action, it won’t keep winning for much longer.

The study is published in the journal Weather.

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