What is the optimum level of CO₂ (ppm) for plants? Plants do love CO₂ up to a point – CO₂ is the raw material for photosynthesis (plant “food”). There isn’t one single “optimum” CO₂ level for all plants, but experiments show that many plant

Plants do love CO₂ up to a point – CO₂ is the raw material for photosynthesis (plant “food”). There isn’t one single “optimum” CO₂ level for all plants, but experiments show that many plants grow faster with more CO₂ until other factors become limiting (like water or nutrients) [climate.mit.edu]. In greenhouse farming, growers often enrich CO₂ to about 1,000–1,200 ppm to boost plant growth, which is roughly where a lot of plants reach near-maximum photosynthesis under ideal conditions [gov.mb.ca]. (For example, around 1200 ppm CO₂ is often cited as a level at which plants photosynthesize at their maximum rate in lab/greenhouse settings [gov.mb.ca].) However, this doesn’t mean more CO₂ is always better in the real world. Outdoors, plants are limited by things like nutrient availability and climate. If a plant doesn’t have enough water or proper nutrients, extra CO₂ won’t help and can even hurt. Also, climate change effects (extreme heat, droughts, etc.) can stress plants and outweigh the growth benefits of higher CO₂ [climate.mit.edu]. In short: some CO₂ increase does stimulate plant growth, but there’s a cap on the benefit. We’re currently at ~420 ppm, which is higher than pre-industrial levels (280 ppm), and indeed satellites have observed some “global greening” partly due to CO₂ fertilization [nasa.gov]. But unlimited CO₂ would not endlessly increase plant growth – most crops hit a saturation point around 1000 ppm in controlled conditions [gov.mb.ca], and real ecosystems depend on a balance of many factors.With increased extreme weather events (draughts, wildfires, hurricanes, flooding etc) driven by global warming, the effects are net negative for stable living conditions.