As the world faces climate change and the loss of natural habitats, many wild animals are threatened with extinction.
A United Nations report calculated that up to one million of the world’s estimated eight million animal and plant species were threatened with extinction, with many likely to disappear within decades.
But it is not all bad news, because some creatures have enjoyed a resurgence in recent years and decades thanks to a focus on helping their numbers to grow.
From the Arabian Oryx, once extinct in the wild but now enjoying population growth, through to the fin whale, which has returned to its former feeding grounds in the Antarctic Ocean in large numbers, there are conservation success stories.
"If you can restore a habitat using a charismatic species as a flagship, lots of other lesser-known species will benefit," said Dan Eatherley, an environmental consultant and author who is researching a book on animals and plants brought back from near-extinction in the UK.
"Often particular species are now being restored not just for their own intrinsic value, but because of ecosystem services they provide.
"There’s a lot of work to bring back oysters because their filter feeding improves water quality, the reefs they build provide vital habitats for other marine life, and they can capture and store carbon. There are all these benefits."
Ahead of Earth Day this month, we consider five successful case histories from land and sea around the globe.
The black rhino in Kenya
In the 1980s, habitat loss and poaching meant that Kenya’s population of black rhinos had fallen to fewer than 350, a tiny fraction of the more than 20,000 that existed in 1970.
However, while numbers are still well short of what they used to be, it was recently announced that there are now 1,000 of the animals in Kenya.
The country, whose government has partnered with conservation organisations such as WWF, is said to be on track to reach its target of having 2,000 black rhinos by 2037.
Conservation programmes, which include monitoring to reduce poaching and veterinary treatment, have been so successful that the 16 sanctuaries in the country where black rhinos live have become overcrowded.
As a result, recently 21 animals were moved from three of these sanctuaries to Loisaba Conservancy, a 58,000-acre game park in northern Kenya that in previous times had black rhinos.
The success story extends beyond Kenya: total numbers of black rhinos and white rhinos in Africa as a whole are increasing, according to the International Union for Conservation of Nature (IUCN), although the organisation continues to classify the black rhino as critically endangered.
Threats remain, including poaching, with WWF reporting that an average of two African rhinos are killed a day.
Climate change is another issue, as higher temperatures will make the animals’ current habitats less hospitable, a study published in January indicated.
"For rhinoceros conservation to be effective, misting stations and wallowing mud pits may be required during peak temperature periods," the study authors wrote in Biodiversity.
The bald eagle in the US
While the bald eagle has been a national symbol of the United States since the 18th century, this bird of prey experienced a devastating drop in its numbers across the country.
Hunting – often carried out because bald eagles were, wrongly, seen as a threat to livestock – and loss of habitat were key reasons for the decline.
Another factor was the insecticide DDT, which the birds ingested when they ate fish contaminated when the chemical was washed into waterways.
Across the 48 "lower states" of the US – all states excluding Alaska and Hawaii – populations of the bird were almost eliminated, with just 417 nesting pairs in 1963.
Prohibitions against hunting, the banning of DDT in 1972 and the introduction the following year of the Endangered Species Act, which protected habitats, and captive-breeding and reintroduction programmes are among the measures credited with helping numbers to recover.
Now there are more than 300,000 bald eagles in the US, according to the US Fish and Wildlife Service, including more than 70,000 breeding pairs.
Arabian oryx in the Middle East
One of the most iconic animals of the Middle East, the Arabian oryx was actually declared extinct in the wild after precipitous declines in numbers that were brought about by hunting, with the last wild example thought to have been shot in 1972.
However, there are now more than 1,200 living in the wild, mostly in the Empty Quarter desert between the UAE and Saudi Arabia. Many thousands more live in semi-captivity.
Numbers have been steadily increasing in areas such as the 6,000-square-kilometre Al Dhafra reserve, the UAE’s largest nature reserve.
Jordan and Oman play host to reintroduced populations of the animal, which is said to be able to smell water from miles away.
The UAE has played a pivotal role in the recovery of the Arabian oryx, through for example the Sheikh Mohamed Bin Zayed Arabian Oryx Reintroduction Programme, which was set up in 2007.
In 2011, thanks to efforts that are ultimately said to have involved at least six countries and five zoos, the International Union for Conservation of Nature changed the status of the Arabian oryx to vulnerable.
This is three categories up from extinct in the wild and the Arabian oryx is the only animal that was once extinct in the wild to have made this level of progress.
Fin whales in the Antarctic
The world’s second-largest mammal after the blue whale, the fin whale was almost wiped out from the southern hemisphere in the 20th century as a result of industrial-scale whaling.
In the early 20th century, before their large-scale killing began in the Antarctic Ocean, the population of fin whales there was about 325,000.
Surveys between 1978 and 2004 found "very few" fin whales in their former feeding grounds in the Antarctic Ocean, but in their 2022 paper, the authors report that their surveys "confirm a return of the whales to their ancestral feeding grounds in high numbers". The animals formed, they wrote, "large feeding aggregations".
Iceland is the only country that still hunts the animals (Norway and Japan carry out commercial whale hunts, but of different species).
Bison in North America
Bison, some weighing more than a tonne each, were a symbol of nature’s extraordinary power, with as many as 100 million of them roaming across the Great Plains of North America. One contemporary observer said that herds in the early 1800s "exceeded imagination".
They were, however, almost driven to extinction thanks to people’s desire for goods made from their leather, and by the end of the 1800s there were fewer than 600 left.
There were factors other than hunting that put bison populations under pressure, including the spread of horses on to the Great Plains as far back as the late 17th century, and drought from the mid-1800s onwards.
But it was hunting, by Native Americans (who began using horses to chase bison) and European settlers (who brought guns with them), that caused a precipitous decline in numbers.
While bison are nothing like as numerous as they used to be, there are now about 500,000 in North America, with a ban on culling introduced in 1969 being a key factor that helped numbers to grow.
European bison too were also almost driven to extinction, but captive-breeding programmes and reintroductions in the wild in countries including Poland and Romania have reversed declines. Bison have also recently been reintroduced to a site in the UK.
