Life in a near-future atmosphere: Carbon dioxide enrichment increases plant growth and alters the behavior of a terrestrial snail but not a terrestrial beetle

In addition to effects on climate and water acidification, anthropogenic atmospheric releases of carbon dioxide may also directly impact terrestrial organisms that use CO ₂ as a chemical cue. We wondered how common organisms would respond to near-future levels of CO ₂ - levels that may occur by 2025. We chose two common but taxonomically and ecologically dissimilar organisms (Theba pisana helicid snails and Adesmia dilatata tenebrionid beetles) to examine the behavioral effects of a slight rise (~10 ppm) of CO ₂ on animal abundance and plant growth in the Negev Desert of Israel. We found that plots with supplementary CO ₂ exhibited greater plant growth than control plots over a 50-day experiment, but increased growth did not alter beetle or snail numbers. In laboratory experiments with higher levels of augmented CO ₂ paired with food rewards, we found that snails did not change their climbing behavior when presented with CO ₂ alone, but they avoided food and climbed away when CO ₂ was paired with food. Beetles in the laboratory were attracted to food regardless of CO ₂ levels although high levels of CO ₂ (1200-1300 ppm) reduced movement. The direct effects of near-future CO ₂ levels may augment plant growth but have only minor influence on terrestrial snails and beetles. However, the effects of CO ₂ on climate change in desert habitats like the Negev may be more severe due to a predicted rise in temperature and a decline in precipitation.