Ecosystem Responses to Elevated Atmospheric CO2

Rising concentrations of atmospheric CO2 drive a cascade of responses across terrestrial ecosystems, influencing plant physiology, soil processes and biogeochemical cycles. Enhanced CO2 availability typically stimulates photosynthesis and plant growth, a phenomenon known as the CO2 fertilisation effect. However, the magnitude and duration of this stimulation are regulated by nutrient availability—particularly nitrogen and phosphorus—and by interactions with water supply, temperature and community composition. In many systems, initial gains in productivity under elevated CO2 are moderated over time by progressive nitrogen limitation, shifts in root allocation and changes in microbial activity. Below ground, increased carbon inputs from roots and litter can alter soil structure, enzyme activities and rates of decomposition, feeding back on nutrient cycling and greenhouse-gas fluxes. Ecosystem models that omit these dynamic feedbacks risk overestimating long-term carbon sequestration. Across biomes, responses vary: in arid regions water savings under elevated CO2 may enhance growth, whereas in nutrient-poor soils the CO2 fertilisation effect can be short-lived. Understanding these complex interactions is vital for predicting the capacity of ecosystems to mitigate climate change and for informing land-management strategies aimed at maximising carbon storage while maintaining ecosystem function.

Research from Nature Portfolio

A global assessment of fine and total root biomass responses to elevated CO2 synthesised data from 24 field experiments spanning diverse climates and soil types. The analysis revealed that aridity substantially curtails the positive response of root systems to elevated CO2, whereas higher soil nitrogen status amplifies fine-root proliferation. Structural equation modelling indicated that water-limited environments may gain little below-ground carbon despite increased atmospheric CO2, emphasising the need to account for regional moisture regimes and soil fertility when projecting ecosystem carbon uptake.

Ecosystem Responses to Elevated Atmospheric CO2 publication trend

The graph below shows the total number of articles in ecosystem responses to elevated atmospheric co2 across all publications each year (not limited to Nature Index journals).

Technical terms

eCO2: Elevated atmospheric carbon dioxide concentration above ambient levels.
FACE (Free Air CO2 Enrichment): An experimental approach exposing ecosystems to higher CO2 in situ without enclosure effects.
Gross nitrogen mineralisation: Microbially mediated conversion of organic nitrogen into ammonium in soil.
Rhizobacterial community: The assemblage of bacterial taxa inhabiting and interacting with plant root systems.
N2O flux: The emission rate of nitrous oxide, a potent greenhouse gas, from soil processes.

References

1. Stimulation of soil gross nitrogen transformations and nitrous oxide emission under Free air CO2 enrichment in a mature temperate oak forest at BIFoR-FACE. Soil Biology and Biochemistry (2023).
2. Plant diversity and functional identity drive grassland rhizobacterial community responses after 15 years of CO2 and nitrogen enrichment. Journal of Ecology (2024).
3. Processes regulating progressive nitrogen limitation under elevated carbon dioxide: a meta-analysis. Biogeosciences (2016).
4. Effects of elevated CO2 on fine root biomass are reduced by aridity but enhanced by soil nitrogen: A global assessment. Scientific Reports (2017).