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To Save Slow-Breeding Giants, Biologists Recommend New Method for Defining Endangered Species

Animals
Asian elephants frolic in Kaudulla Wewa at Kaudulla National Park in central Sri Lanka. David Stanley / CC BY 2.0

When it comes to saving some of the planet's largest animals, a group of researchers says that old methods of conservation just won't cut it anymore.


Typically, conservationists use a methodology called population viability analysis (PVA), a species-specific risk assessment that considers when a particular population will go extinct given certain perimeters. A new study published in the Journal of Frontiers in Ecology and Evolution suggests that basing conservation decisions simply on low population counts in slow-breeding animals could cause irrevocable decline.

"Critical thresholds in so-called vital rates — such as mortality and fertility rates among males and females of various ages — can signal an approaching population collapse long before numbers drop below a point of no return," said lead author Dr. Shermin de Silva, adding that conservation efforts for megafauna should be aimed at maintaining their "demographic safe space." That is, a combination of key vital rates, such as offspring survival rate and habitat loss, that support population increases rather than short-term trends in population size and distribution

To come to this conclusion, de Silva and her team analyzed endangered Asian elephants as a case study, whose populations are thought to have been halved in less than a century. Today there are fewer than 50,000 wild Asian elephants, in part because they breed extremely slowly — oftentimes just one calf every six years or more. Mathematical modeling of near-optimal reproduction and high survival rates for calves determined that Asian elephant populations cannot tolerate losing more than 7.5 percent of females annually.

It leads to something de Silva calls a "demographic tipping point," the combination of vital rates that helps us understand how populations are impacted by a variety of environmental and human influences.

"Even large populations, if in decline, will eventually pass a point of no return that is difficult to predict in advance. Rather than wait for this eventuality, we suggest that demographic tipping points, and the corresponding safe spaces they define, can offer impetus to act early even when data are scarce," write the authors. Basing conservation approaches off of current trends in population and range is misleading for these types of animals because "short-term fluctuations may mask long-term trends" and even decisions made with the best of intentions may be ill-informed.

Their large body size makes the Asian elephant (Elephas maximus) an influential and vulnerable member of the ecosystem whose threats include overharvest, habitat loss and their time-consuming lifecycle. These megafauna need "proactive management" well before their numbers become critically low.

"But while the attention of the world has been focused on the ivory trade, for critically endangered Asian elephant populations the greatest threat is habitat loss — followed by illegal trade in live animals and parts," said de Silva, adding that habitat loss creates an "extinction debt" that slows down birth rates and increases mortalities. For these long-living species that are slow-to-breed, even small changes can make a profound difference.

This application of conservation could also be applied to other keystone species like giraffes, rhinos and eastern gorillas.

Correction: An earlier version of this story inaccurately referred to de Silva as a "him" instead of "her." The story has been corrected

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A volcano erupts on New Zealand's Whakaari/White Island on Dec. 9, 2019. Michael Schade / Twitter

A powerful volcano on Monday rocked an uninhabited island frequented by tourists about 30 miles off New Zealand's coast. Authorities have confirmed that five people died. They expect that number to rise as some are missing and police officials issued a statement that flights around the islands revealed "no signs of life had been seen at any point,", as The Guardian reported.

"Based on the information we have, we do not believe there are any survivors on the island," the police said in their official statement. "Police is working urgently to confirm the exact number of those who have died, further to the five confirmed deceased already."

The eruption happened on New Zealand's Whakaari/White Island, an islet jutting out of the Bay of Plenty, off the country's North Island. The island is privately owned and is typically visited for day-trips by thousands of tourists every year, according to The New York Times.

Michael Schade / Twitter

At the time of the eruption on Monday, about 50 passengers from the Ovation of Seas were on the island, including more than 30 who were part of a Royal Caribbean cruise trip, according to CNN. Twenty-three people, including the five dead, were evacuated from the island.

The eruption occurred at 2:11 pm local time on Monday, as footage from a crater camera owned and operated by GeoNet, New Zealand's geological hazards agency, shows. The camera also shows dozens of people walking near the rim as white smoke billows just before the eruption, according to Reuters.

Police were unable to reach the island because searing white ash posed imminent danger to rescue workers, said John Tims, New Zealand's deputy police commissioner, as he stood next to Prime Minister Jacinda Ardern in a press conference, as The New York Times reported. Tims said rescue workers would assess the safety of approaching the island on Tuesday morning. "We know the urgency to go back to the island," he told reporters.

"The physical environment is unsafe for us to return to the island," Tims added, as CNN reported. "It's important that we consider the health and safety of rescuers, so we're taking advice from experts going forward."

Authorities have had no communication with anyone on the island. They are frantically working to identify how many people remain and who they are, according to CNN.

Geologists said the eruption is not unexpected and some questioned why the island is open to tourism.

"The volcano has been restless for a few weeks, resulting in the raising of the alert level, so that this eruption is not really a surprise," said Bill McGuire, emeritus professor of geophysical and climate hazards at University College London, as The Guardian reported.

"White Island has been a disaster waiting to happen for many years," said Raymond Cas, emeritus professor at Monash University's school of earth, atmosphere and environment, as The Guardian reported. "Having visited it twice, I have always felt that it was too dangerous to allow the daily tour groups that visit the uninhabited island volcano by boat and helicopter."

The prime minister arrived Monday night in Whakatane, the town closest to the eruption, where day boats visiting the island are docked. Whakatane has a large Maori population.

Ardern met with local council leaders on Monday. She is scheduled to meet with search and rescue teams and will speak to the media at 7 a.m. local time (1 p.m. EST), after drones survey the island, as CNN reported.