What was done
The authors reviewed the scientific literature related to plant responses to atmospheric CO2 enrichment that may have direct or indirect influences on the species richness of earth's ecosystems.

What was learned
No evidence was found to suggest that atmospheric CO2 enrichment adversely affects genetic diversity within individual plant species, nor that it negatively impacts ecosystem species richness.  Instead, it was found that more CO2 in the air tends to stimulate belowground biological activities that tend to increase ecosystem biodiversity.  It was also shown how increases in the air's CO2 content tend to ameliorate heat stress in plants and relieve the need they might otherwise have to migrate poleward (or to higher elevations) to avoid high-temperature-induced extinction.  Evidence was also found to suggest that a similar phenomenon was occurring in certain animals; and it was demonstrated how the aerial fertilization effect of earth's rising atmospheric CO2 concentration was enhancing plant productivity and thereby helping both herbivores and carnivores maintain the population sizes required to preserve their genetic identity as distinct species.

What it means
The lack of CO2-induced negative influences on ecosystem biodiversity and the presence of numerous positive influences induced by atmospheric CO2 enrichment suggests that the ongoing rise in the air's CO2 content is helping the biosphere maintain its species richness.  Hence, as earth's plants and animals are engaged in a continuous struggle to survive the many truly negative impacts of humanity on their numbers, it is imperative that this one very positive effect of our presence on the planet, i.e., our release of CO2 to the air as a consequence of our burning of fossil fuels, be allowed to continue unrestricted by ill-conceived policies such as the Kyoto protocol.