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Feb. 5 (UPI) -- Earth's giants, the largest plant and animal species, tend to be the planet's most vulnerable. New research suggests the loss of giant species would also accelerate the degradation of vulnerable ecosystems. To save the planet, authors of a new study recommend prioritizing the protection of Earth's giants.
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For the study, published Tuesday in the journal Nature Communications, scientists used a computer model to study how the loss of large plant and animal species has impacted ecological health across long time scales.
The simulations allowed researchers to compare the health of the natural world during the Pleistocene, when many more large species roamed Earth, to the health of global ecology today. With analysis of the past and present as a guide, the model simulated the state of nature on a future planet Earth -- a world in which large plants and animals have gone extinct.
The model showed the continued loss of large plant and animal species is likely to yield a 44 percent reduction in Earth's total biomass of wild animals. Simulations also showed soil fertility is likely to decline 92 percent if the planet's largest species continue to disappear.
"This research shows there are fundamental scientific principles that explain why large animals and trees matter for the health and integrity of all life on Earth," lead study author Brian Enquist, professor of ecology and evolutionary biology at the University of Arizona, said in a news release. "Protecting big, charismatic species does have an umbrella effect to protect the wider ecosystem."
Previous studies have highlighted the reasons for the link between large species and ecological health. Earth's giants help transport nutrients.
By eating and excreting in different places, the animal kingdom works like a giant compost bin. And the largest animals, especially those that travel great distances, play an especially big role in the process.
Earth is less fertile today, research suggests, because there are fewer big species -- and big bowel movements -- transporting and recycling nutrients.
According to authors of the new study, the largest trees are also the most productive, storing large amounts of carbon and helping replenish soil nutrients.
"Ecosystems with larger trees and animals are also more productive and provide more vital ecological services," Enquist said. "I use this analogy: The largest banks and corporations in the economy are the most productive and have the most impact on the economy, so when those large banks failed during the great recession in 2009, we had to prop them up economically, or they would have had a disproportionate negative impact on economy. It's a similar principle with large plants and animals across ecosystems."
Unfortunately, the largest plant and animal species are also the most susceptible to human pressures, including habitat loss, hunting, logging and climate change. The latest research echoes the findings of previous studies that showed human influences have been negatively impacting Earth's largest animals for thousands of years.
"In the last few thousand years, these large animals and plants have been whittled away, and this process continues today," said Yadvinder Malhi, leader of the ecosystems group at the University of Oxford's Environmental Change Institute. "Our paper shows why this loss of these giants matters for the very fabric of life on Earth, and why we must do everything possible to protect and restore them."
Some conservationists have criticized the prioritization of larger, more charismatic species, like tigers and redwood trees, but the latest research suggests work to save larger species can have significant benefits for entire ecosystems.
"Our findings point to the importance of policies that emphasize the promotion of large trees and animals, as such policies will have a more disproportionate impact on biodiversity, ecosystem processes and climate mitigation," Enquist said. "We can use this model to focus our conservation concerns. For example, we can identify the forest that still contains some of the largest tress on the planet, or forests that have healthy size structure and prioritize them because they're more productive and resilient."
