Nairobi / Berlin / Cambridge (AP) - The death of rhinoceros Sudan last year in Kenya went around the world. Among the animals, the bull was a celebrity: Sudan was the last male Northern White Rhinoceros on Earth.

With his death, the subspecies almost died out. But science could possibly save them - because there are still two females and frozen sperm. Scientists in Berlin are working with modern technology to create a small Northern White Rhinoceros.

To increase biodiversity in the world, some researchers go one step further: animals that have been extinct for thousands of years, should be revived. At Harvard and Santa Cruz, researchers are using genetic engineering to raise the woolly mammoth or the migrant pigeon.

But science is deeply divided: Is that still conservation? Or are we engaging too much in nature?

Northern white rhinos once migrated in large numbers through East and Central Africa, poachers eradicated them. Now the fate of the subspecies lies in a Petri dish: researchers at the Berlin Leibniz Institute for Zoo and Wildlife Research (IZW) want to fertilize the last females in Kenya in the laboratory with sperm from already deceased males. A female of the closely related Southern White Rhinoceros could carry the baby.

First, the methods would be tested, explains Steven Seet from the IZW. Eggs were taken from Southern White rhinos in zoos and fertilized with Northern White Rhinoceros sperm. The hybrid embryo was then implanted in a female Southern White Rhinoceros. The transfer had been successful, but it was not clear whether the embryo had lodged in the uterus. At the same time, researchers at the Max Delbrück Center for Molecular Medicine are working on stem cell technology to grow sperm and oocytes from preserved rhino body cells. Only then could one produce a genetic diversity that would be large enough to build a population.

The rescue attempts are now supported by around four million euros from the Federal Ministry of Education and Research (BMBF). "Biodiversity is our livelihood," said Michael Meister, Parliamentary State Secretary to the Federal Minister, on Tuesday in Berlin. Therefore, the ministry would promote preventive research on biodiversity conservation and emergency measures to protect endangered species, he said.

Six thousand miles away, in a Harvard University lab in Boston, an animal that has been extinct for ten thousand years is being revived: the woolly mammoth. Behind it is George Church, superstar among the geneticists. The animal is not cloned, but the genetic material found in mammoths is not enough. Instead, Church and his team extract certain DNA parts of the mammoth genome and insert them into cells of elephants. They use new technologies such as the gene scissors CRISPR-Cas9, with which DNA can be cut in a targeted manner.

Strictly speaking, no mammoth is created, but a completely new animal. "We're trying to create an elephant that is resistant to cold and poaching," says Church. One could reduce the size of the tusks in the animal to reduce the risk of poaching. However, at the earliest in four years, there could be first results that resemble elephants.

Meanwhile, on the US West Coast Ben Novak wants to revive the pigeon with similar methods. It once traveled in huge swarms over America, but was eradicated at the end of the 19th century. It will probably take another five to ten years to reach the first chicks, says the University of California researcher in Santa Cruz. "After 2025 is possible, but probably closer to 2030."

The only animal subspecies that has been revived so far is the Pyrenean Stone buck. The last animal died in 2000, previously a cell sample was taken for cloning and frozen. The fawn cloned from it - carried by another Capricorn variant - lived only a few minutes after the cesarean birth.

Proponents of de-extinction - the revival of extinct species - assure that it's not about headlines. "We want to use biotechnologies to help conserve nature and create more biodiversity," says Revive and Restore director Ryan Phelan, who supports projects such as the mammoth or the pigeon trek.

But many scientists turn up their noses. "It's a waste of time," says evolutionary biologist Stuart Pimm of Duke University in Durham, NC. To protect species from extinction, one must solve the real problem: the conflict between humans and animals. The research of Church and Co creates a dangerous negligence. "If you can eradicate and revive a species, then you're not so concerned about keeping the species in the wild." He also asks, "What would we do with a woolly mammoth?"

Church already has an idea. He wants to settle the mammoth elephant in Siberia. Thus, a huge, barely inhabited area is used to create an ecosystem for a new species. And: "We would help to slow down climate change." Because: The mammoths would tamp the snow and thus make the thawing of the soil more difficult. As a result, fewer greenhouse gases such as carbon dioxide and methane would escape to the atmosphere.

Nikita Simow is waiting eagerly for the newcomers. The Russian scientist manages a huge sanctuary in eastern Siberia, where one day a grassy landscape will grow again - like the last ice age, when mammoths roamed the region. "Church has promised that the first mammoth will arrive in the Pleistocene Park." However, a single animal is not enough to fight climate change, says Simov: "To make a decisive impact on the global climate, it takes thousands, hundreds of thousands."

Organization Revive & Restore

Research project on the pigeon

Research project on woolly mammoth