Accelerating extinction rate triggers domino effect of biodiversity loss
While nearly one million species are currently at risk of extinction, the United Nations University (UNU) in Bonn is drawing attention to “co-extinctions”: the chain reaction occurring when the complete disappearance of one species affects another.
The issue is in the spotlight ahead of the International Day for Biological Diversity, observed annually on 22 May, and covered in the most recent edition of UNU’s Interconnected Disaster Risks report.
Among the animals at risk is the gopher tortoise, one of the oldest living species on the planet. This tragic story of biodiversity loss is unfolding at the heart of the coastal plains of the southern United States.
Ecosystem ‘architect’
Their reduced number is not just problematic for the survival of the tortoise as a species, however, as these charismatic creatures also play a vital role in preserving the delicate balance of their coastal realm.
Gopher tortoises are not merely occupants of their habitat; they are architects, sculpting ecosystems and providing sanctuaries for over 350 other species. With their front legs functioning like shovels, they dig burrows that range in size from 20 to 30 feet (6 to 9 metres) long and from 6 to 8 feet (1.8 to 2.5 metres) deep.
From small insects to larger amphibians, each organism plays a vital role in the ecosystem's intricate web of life these burrows provide. For some, the burrows of the gopher tortoise are a safe haven for breeding and nurturing offspring, while for others, they offer respite from predators and the elements.
Should the gopher tortoise vanish, it is likely a domino effect would be felt throughout the ecosystem.
Among the most vulnerable is the critically endangered dusky gopher frog, a species already teetering on the brink of extinction. Reliant on the tortoise's burrows for shelter and survival, the disappearance of the tortoise would most likely put the frog’s survival at risk too.
The role of humans
In shedding more light on co-extinctions, UNU said that intense human activities, such as land-use change, overexploitation, climate change, pollution and the introduction of invasive species, is causing an extinction acceleration that is at least tens to hundreds of times faster than the natural process of extinctions.
In the last 100 years, over 400 vertebrate species were lost, for example. The report therefore includes accelerated extinctions among its six interconnected ‘risk tipping points’.
Such points are reached when the systems that humanity relies on cannot buffer risks and stop functioning like expected – mainly as a result of human actions.
Extinction breeds extinction
Ecosystems are built on intricate networks of connections between different species, as the gopher tortoise-dusky gopher frog example indicates.
The domino effect could lead to more species going extinct and eventually even to the collapse of entire ecosystems.
With nearly one million plant and animal species currently under threat, the ripple effect of the extinction of a single species can affect countless others, disrupting vital ecological functions.
The endangered sea otter provides another example of intricate dependencies within ecosystems. Calling the Pacific kelp forests their home, they were once plentiful, but are now locally endangered due to being relentlessly hunted for their fur in the past.
In a finely tuned ecological dance, sea otters prey on sea urchins, halting the unrestrained growth of sea urchin populations. Without the presence of otters, these spiky grazers run rampant, transforming lush kelp forests into desolate ‘urchin barrens’.
But the demise of sea otters would have impacts that extend far beyond the disappearance of kelp alone, UNU said. Over1,000 species– including sharks, turtles, seals, whales, birds, and a multitude of fish– rely on these underwater havens for their very existence.
Creating the future we want
Addressing the biodiversity crisis demands a multifaceted approach that recognizes the interconnectedness of risks and solutions.
The theme of the International Day for Biological Diversity calls for everyone to support implementation of the Biodiversity Plan, adopted in 2022, which sets goals and concrete measures to stop and reverse the loss of nature by 2050.
One of the goals includes reducing the extinction rate of all species tenfold by mid-century and increasing the abundance of native wild species to healthy and resilient levels, said Zita Sebesvari, Deputy Director of UNU’s Institute for Environment and Human Security and lead author of the Interconnected Disaster Risks report.
“While adaptation strategies, such as restoring and protecting green corridors between animal habitats offer some respite, tackling underlying drivers of extinction remains crucial, because this goal cannot be reached as long as we risk accelerating extinctions,” she explained.
In the long term, avoiding extinctions and co-extinctions will be the only realistic solution to halt biodiversity loss, which requires a shift of mindsets.
“Conservation efforts must extend beyond individual species to encompass entire ecosystems”, Ms. Sebesvari said.
“Urgent and decisive action is needed to preserve the resilience of ecosystems and ensure the survival of our planet’s diverse web of life. Embracing nature as an integral part of our culture is essential to secure a sustainable future, recognizing that our fate is inevitably intertwined with the fate of the natural world.”