Models have been too optimistic as they have not recognised that cold temperatures or water are more fundamental constraints on growth than carbon supply.
Terrestrial ecosystems accounted for more than half of the global carbon sink during the past six decades, and substantially mitigated climate change. But a study which looked at long-term satellite and ground-based datasets has shown that carbon fertilisation has declined across most regions from 1982 to 2015. This is linked to changing nutrient concentrations, especially nitrogen and phosphorous, and the availability of soil water the study, carried out by an international team of scientists, found. The decline is more pronounced in cold areas and grasslands and less in the tropics, where water and nutrients are still available to support growth.
The researchers say that the work has policy implications in clarifying climate models so that they do not overestimate future carbon sinks, because that would give the idea that global warming will accelerate more slowly. Models have been too optimistic as they have not recognised that cold temperatures or water are more fundamental constraints on growth than carbon supply.
‘Biomass on land has been increasing and offsetting about a quarter of our emissions from industry, which is of great benefit to society, but prompts concerns as to whether this will continue,’ said Britt Stephens, an atmospheric researcher at the National Centre for Atmospheric Research, Boulder, Colorado, US. He notes that carbon uptake increases will continue, but just not as steeply as in previous decades.
For more on this visit C&I