The author is Ellen Welty, a regional ecologist who studies grassland insects and plants. She is part of the Great Plains Science Program, based in the prairies of north-central Montana. She conducts observational monitoring of grasshoppers, dung beetles, wolf spiders, plant composition, and plant biomass. Her research interests include insect function in grasslands, plant-insect interactions, ecological time series, and plant and insect responses to altered biogeochemistry. Originally published by The Conversation.
More than a third of all animals on Earth, from beetles to cows to elephants, rely on plant-based diets. Because plants are a low-calorie food source, it can be difficult for animals to expend enough energy to meet their needs. Currently, climate change is reducing the nutritional value of some of the foods that plant-eaters rely on.
Human activities are increasing the concentration of carbon dioxide in the atmosphere, causing global temperatures to rise. As a result, many plants are growing faster across ecosystems around the world.
Some studies suggest that this “greening of the planet” could partially offset increases in greenhouse gas emissions by storing more carbon in plants. However, there are trade-offs. These fast-tracking plants can contain fewer nutrients per bite.
I’m an ecologist and my colleagues and I are investigating how nutrient dilution affects species across food webs. We focus on the responses of plant-feeding populations, from tiny grasshoppers to giant pandas.
We believe that long-term changes in plant nutritional value may be an underestimated cause of animal population declines. These changes in vegetation are as invisible as sea level rise. Nor is it sudden and imminent, like a hurricane or heat wave. However, it can have important effects over time.
Plant-eating animals need more time to find and consume food when their regular diet is less nutritious, and can be exposed to greater risks from predators and other stresses in the process . Reduced nutritional value can also reduce an animal’s health and ability to grow, reproduce, and survive.
Increase in carbon and decrease in nutrients
Studies have already shown that climate change is causing a dilution of nutrients in human food crops. Depletion of micronutrients, which play important roles in growth and health, is of particular concern. Long-term records of crop nutritional values revealed declines in copper, magnesium, iron, and zinc.
In particular, human iron, zinc, and protein deficiencies are expected to increase in the coming decades due to rising carbon dioxide levels. These declines are expected to have far-reaching implications for human health and even survival, with the effects likely to be strongest among populations that are highly dependent on rice and wheat, particularly in East and Central Asia. is expected.
The nutritional value of livestock feed is also decreasing. Because cows spend a lot of time eating, they often struggle to find enough protein to meet their needs. Grass protein concentrations in rangelands around the world are declining. This trend threatens both livestock and ranchers, reducing animal weight gain and creating costs for producers.
Nutrient dilution also affects wild species. Here are some examples:
dependent on bamboo
Giant pandas are an endangered species with great cultural value. Because they have a low reproductive rate and require extensive interconnected bamboo forests as habitat, they are classified as a vulnerable species whose survival is threatened by land conversion for agriculture and development. Pandas could also be the animals that advertise the threat of nutrient dilution.
Giant pandas are considered an “umbrella species,” meaning that protecting their habitat also benefits many other plants and animals that live in bamboo forests. It is well known that giant pandas are completely dependent on bamboo and spend most of the day eating bamboo. Currently, rising temperatures are reducing the nutritional value of bamboo, making it difficult for the plant to survive.
The outlook for insects is mixed
Insects are important members of the web of life, pollinating many flowering plants, serving as a food source for birds and animals, and performing other important ecological services. Around the world, many insect species are declining not only in natural areas but also in developed areas where habitats have been converted to farms and cities.
In areas less affected by human activity, there is evidence to suggest that chemical changes in plants may play a role in declining insect populations.
Many insects are plant eaters and can be affected by reduced nutritional value of plants. Experiments have found that as carbon dioxide levels rise, insect populations decline, at least in part due to a decline in the quality of the food supply.
However, not all insect species are in decline, and not all plant-eating insects respond to nutrient dilution in the same way. Insects that chew on leaves, such as grasshoppers and caterpillars, are most adversely affected, including decreased fertility and reduced body size.
In contrast, locusts prefer carbon-rich plants, so rising carbon dioxide levels can cause increased locust outbreaks. Some insects, such as aphids and cycads, feed on phloem (the living tissue inside plants that carries food made in the leaves to other parts of the plant) and can also benefit from carbon-rich plants. There is a gender.
uneven impact
Declines in the quality of plant foods are most likely to impact places where there are already nutritional deficiencies and animals struggle to meet their nutritional needs. These zones include tropical regions such as the Amazon and the Congo Basin, as well as ancient soils from Australia. Nutrient dilution is also a problem in the open ocean, with rapid warming of seawater reducing nutrients for giant sea kelp.
Certain types of herbivores may face greater declines because they require higher quality food. Rodents, rabbits, koalas, horses, rhinos, and elephants are all hindgut fermenters, meaning they have simple, single-chambered stomachs and rely on microbes in their guts to extract nutrients from high-fiber foods. It’s an animal.
These species require more nutritious food than ruminants, which are herbivores such as cows, sheep, goats, and bison, which have four-chambered stomachs that digest food in stages. Small animals also have faster metabolisms and consume more energy per unit of body weight, so they usually require more nutritious food than larger animals. Small animals also have short intestines, so they cannot easily extract all the nutrients from their food.
Understanding how nutrient dilution plays a role in the decline of individual species requires experiments that artificially increase carbon dioxide levels or long-term changes in plant chemistry in parallel with animals in the field. Further research is needed, including studies that monitor
In the long term, how is nutrient dilution causing changes throughout the food web, including changes in plant species and traits, effects on other animal groups such as predators, and changes in interactions between species? It will be important to understand. Changes in plant nutritional value due to rising carbon dioxide levels can have far-reaching effects across ecosystems around the world.
