\u201cWhen we look at future climate change, it\u2019s not the same as the current hot years that we experience,\u201d said Alex Ruane, co-director of NASA\u2019s Goddard Institute for Space Studies\u2019 Climate Impacts Group. \u201cIf we were to find a location and look at a hot year that was recently experienced, it would likely have been a heat wave that would have raised the overall temperature. Climate change is different. Climate change is every day, a little bit more and more. When those heat waves come [in the future], they\u2019re just a little bit more intense or extreme, and that has a different physiological impact [on plants].\u201d<\/p>\n
Welti said changes in plants\u2019 long-term nutritional value could be one underappreciated cause of falling animal populations.<\/p>\n
\u201cThese changes in plants aren\u2019t visually evident, like rising seas. Nor are they sudden and imminent, like hurricanes or heat waves. But they can have important impacts over time,\u201d Welti said in The Conversation. \u201cPlant-eating animals may need more time to find and consume food if their usual meal becomes less nutritious, exposing themselves to greater risks from predators and other stresses in the process. Reduced nutritional values can also make animals less fit, reducing their ability to grow, reproduce and survive.\u201d<\/p>\n
The nutrient value of livestock feed has also been declining. It is often difficult for cattle \u2014 who spend much of their time eating \u2014 to find enough protein, as protein concentrations are falling across rangelands all over the planet, threatening livestock and ranchers.<\/p>\n
Nutrition dilution also affects wild species like some insects.<\/p>\n
\u201cInsects are essential members of the web of life that pollinate many flowering plants, serve as a food source for birds and animals, and perform other important ecological services. Around the world, many insect species are declining in developed areas, where their habitat has been converted to farms or cities, as well as in natural areas,\u201d Welti explained. \u201cMany insects are plant feeders that are likely to be affected by reduced plant nutritional value. Experiments have found that when carbon dioxide levels increase, insect populations decline, at least partly due to lower-quality food supplies.\u201d<\/p>\n
Leaf-chewing insect species like caterpillars and grasshoppers suffer the most negative impacts, from smaller body sizes to reduced reproduction.<\/p>\n Other insects like cicadas and aphids could benefit from carbon-rich plants.<\/p>\n \u201cCertain types of plant-feeding animals are likely to face greater declines because they need higher-quality food. Rodents, rabbits, koalas, horses, rhinoceroses and elephants are all hind-gut fermenters \u2013 animals that have simple, single-chambered stomachs and rely on microbes in their intestines to extract nutrients from high-fiber food,\u201d Welti added.<\/p>\n Welti said more research will be necessary to understand the role of nutrient dilution in the declines of individual species.<\/p>\n \u201cOver the longer term, it will be important to understand how nutrient dilution is altering entire food webs, including shifts in plant species and traits, effects on other animal groups such as predators, and changes in species interactions. Changes in plant nutritional value as a result of rising carbon dioxide levels could have far-reaching impacts throughout ecosystems worldwide,\u201d Welti said.<\/p>\n