Expert Debunks Viral TikTok Claim That CO2 ‘Greening’ Means Net Benefit: ‘Too Complex For A One-Size-Fits-All Law’

A TikTok exchange between two creators — former climate activist Lucy Biggers (@lucybiggers) and Emma (@simpleenvironmentalist) — reignited debate over whether rising atmospheric carbon dioxide (CO2) is an unambiguous benefit because it can stimulate plant growth. Biggers posted charts showing global "greening" and a conceptual model linking CO2 to vegetation growth; Emma replied with a fact-check arguing the studies were shown without important caveats.

What The Clips Showed

Biggers displayed a NASA-based map of global "greening," highlighting regions where satellite data show increased leaf area and vegetation cover. She also shared a conceptual diagram that suggested higher atmospheric CO2 correlates with higher greening rates across historical and projected CO2 levels.

The Science: Carbon Fertilization — Real, But Limited

It is correct that CO2 is a raw material for photosynthesis: plants use CO2, water and sunlight to produce sugars and oxygen. In many controlled experiments, elevated CO2 increases photosynthetic rates and biomass — a phenomenon called the carbon fertilization effect. That can mean more leaves or larger root systems in some species under some conditions.

But experts stress several important limits and trade-offs:

• Diminishing Returns: Several studies note much larger growth responses when CO2 rises from very low levels up to modern concentrations than when it rises above current levels. As the paper quoted in Emma's video put it:

  "Most studies … report much greater physiological and growth enhancements in response to increases in [CO2] below modern concentrations than to increases above modern concentrations. Thus, plants may have already exhausted much of their potential to respond to rising [CO2]."

• Nutrient Dilution: Increased biomass does not automatically mean healthier crops. Plants grown under elevated CO2 often have lower concentrations of protein, iron and zinc, reducing nutritional value for humans and wildlife.
• Other Limiting Factors: Water availability, soil fertility, temperature, pests and disease strongly influence whether additional CO2 translates into more growth. If any of those factors are limiting, CO2 benefits will be reduced or absent.

Climate Context Matters

Burning fossil fuels raises atmospheric CO2 and traps heat, driving global warming. Higher average temperatures and shifting weather patterns increase the frequency and intensity of extreme events — droughts, floods and storms — that can harm crops despite any localized greening. The article cites recent real-world impacts: heavy rains that destroyed thousands of hectares of crops in Bangladesh and prolonged drought that damaged pastures in parts of Illinois.

Why Context And Communication Matter

As MIT environmental engineer David Des Marais told Climate Fact Checks, "Plant growth is too complex for a one-size-fits-all law." The TikTok exchange illustrates how charts from reputable studies can be misleading when stripped of qualifiers and limits. Social platforms amplify simple narratives; accurate interpretation requires attention to experimental conditions, geographic variability and interacting environmental pressures.

Bottom Line: CO2 can boost photosynthesis in many controlled settings, but benefits are neither uniform nor guaranteed in the real world. Nutrient dilution, diminishing returns at current CO2 levels, and increasingly extreme weather tied to fossil-fuel emissions mean that rising CO2 is not a silver lining that offsets the broader risks of climate change.