Rising carbon dioxide may be diluting plant nutrients, threatening herbivores

(Press-News.org) Smithsonian Conservation Research Brief: 
Carbon dioxide-fueled accelerated plant growth dilutes nutrients, impacting herbivore populations. 

A new study from researchers at the Smithsonian’s National Zoo and Conservation Biology Institute (NZCBI) warns that as human activities increase carbon dioxide (CO2) levels in the atmosphere, they may decrease the nutrient contents of plants. Declines in nutrient content, known as Nutrient Dilution, may already be harming plant-eating animals and could cause further population declines farther up the ecological chain. The paper, published today in the journal Trends in Ecology & Evolution, examines evidence for Nutrient Dilution, its causes and its impacts on herbivore populations globally.   

Research Paper 
Title: “Nutrient dilution and the future of herbivore populations” 
Published: Trends in Ecology & Evolution 
For citations: https://doi.org/10.1016/j.tree.2024.05.001 

Abstract:

Nutrient dilution (ND) – the decrease in the concentration of nutritional elements in plant tissue – arises from an increase in the mass of carbohydrates and/or a decrease in the 20+ essential elements. Increasing CO2 levels and its promotion of biomass are linked to nutrient dilution. We build a case for nutrient dilution as a key driver in global declines in herbivore abundance. Herbivores must build element-rich animal tissue from nutrient-poor plant tissue, and their abundance commonly increases with fertilization of both macro- and micronutrients. We predict the global impacts of nutrient dilution will be magnified in some of Earth’s most biodiverse, highly productive, and/or nutrient-poor ecosystems and should favor specific traits of herbivores, including sap-feeding and ruminant microbiomes. 

Quote from Ellen Welti, senior author and conservation ecologist, Smithsonian’s National Zoo and Conservation Biology Institute’s Conservation Ecology Center:   

“This is yet another major issue caused by humans pumping excess CO2 into the air: Humans’ and natures’ food base being reduced in quality. Nutrient Dilution should be added to the list of major threats to biodiversity from climate change.” 

“Many herbivores are already right at the nutritional knife’s edge, where they get just enough from their food to survive. If the nutrient content of food that is already low decreases, there becomes a point where animals can’t compensate by simply eating more.”
 
Authors 
Michael Caspari (1)(2), Ellen Welti (2)  

School of Biological Sciences, University of Oklahoma, Norman, OK 73019, USA 

Conservation Ecology Center, Smithsonian’s National Zoo and Conservation Biology Institute, Front Royal, VA 22630, USA 

About the Smithsonian’s National Zoo and Conservation Biology Institute   
The Smithsonian’s National Zoo and Conservation Biology Institute (NZCBI) leads the Smithsonian’s global effort to save species, better understand ecosystems and train future generations of conservationists. Its two campuses are home to some of the world’s most critically endangered species. Always free of charge, the Zoo’s 163-acre park in the heart of Washington, D.C., features 2,200 animals representing 400 species and is a popular destination for children and families. At the Conservation Biology Institute’s 3,200-acre campus in Virginia, breeding and veterinary research on 264 animals representing 20 species provide critical data for the management of animals in human care and valuable insights for conservation of wild populations. NZCBI’s more than 300 staff and scientists work in Washington, D.C., Virginia and with partners at field sites across the United States and in more than 30 countries to save wildlife, collaborate with communities and conserve native habitats. NZCBI is a long-standing accredited member of the Association of Zoos and Aquariums. 

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