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Grizzlies and polar bears are breeding thanks to climate change

Rising temperatures are simultaneously driving grizzly bears north and polar bears south, prompting interbreeding between both species. Conservationists are weighing up the possibility of controlling genetic adaption to help animals of the future cope with climate change.

From time to time, it’s good to remind ourselves that climate change isn’t just an imminent threat to humanity.

The ramifications of a warming world are constantly throwing delicate ecosystems off balance, and mother nature’s capacity to adapt and thrive at all costs manifests in a number of ways.

When it comes to endangered animals, we’re increasingly recording new instances of spontaneous interbreeding between species – sometimes leading to new types of hybrid offspring popping up, which are more naturally equipped to handle a warmer climate.

With bears in particular, interbreeding has become far more common in the last year or so. As Arctic sea ice thins, starving polar bears are being driven south where they in-turn encounter grizzlies seeking out cooler territories. No prizes for guessing what happens next.

As they inter-populate in greater numbers, the odds of mating occurring obviously go up. In Alaska and Canada, two regions where this has become relatively common, the number of ‘grolar’ or ‘pizzly’ – choose your progeny preference – sightings has rapidly grown since the first recorded observation in 2006.

The mixing of these two native species creates a short-furred hybrid that is more adept at handling hot temperatures than the grizzly, and better at foraging for food (that isn’t purely blubber based) than the polar bear, thanks to its modified skull shape and teeth.

These crossbreeds don’t purely onboard all of their parents’ best traits, however, as pizzlies have been found to be less adept at swimming than polar bears.

Beyond these giant mammals, there has been numerous instances of interbreeding reportedly creating hybrid wildlife more accustomed to climate change.

This has led conservationists to reignite old debates on whether this practice should in-fact be encouraged and controlled, or not.

Should interbreeding be encouraged?

Those in favour of cross-breeding endangered animals lean on the argument that it is strictly for their own good and guaranteed prosperity.

‘Lots of things hybridise all the time,’ says Michelle Marvier, a conservation biologist at Santa Clara University in California.

It happens in plants, fish, and amphibians, as well as mammals. In-fact, many of us carry traces of Neanderthals and Denisovans in our DNA, proof that we mixed with other human species thousands of years ago.

In a recent experiment on rapid coral degradation, expert Van Oppen discovered that cross breeding corals under laboratory conditions created a hybrid far more resistant to heat than the parents alone. Under duress, they survived up to 34% better at high temperatures and CO2 levels.

While these results are certainly promising, the opposing argument is concerned that interbreeding – especially with endangered animals – is a slippery slope that may counter-intuitively quicken extinction rates.

Over time, the continuous splicing of original DNA with the genes of newcomers will inevitably dilute the initial trace. In the case of our bears, the polar bear population is already projected to diminish by more than 30% in the next 30 years.

It’s reasonable to suggest that in this time, grizzlies and polar bears will begin to co-exist in greater numbers. This will lead to huge spikes in the pizzly population, and as generations pass, potentially a complete dominance in the gene pool.

Yes, pizzlies have proven capable of birthing their own.

This theory is given credence by a recent study into Europe’s wildcat population, which is constantly shrinking due to cross-breeding with domestic cats.

It’s now down to those who’re invested in the prospect of controlled interbreeding to prove that hybrids will not subsume both halves of their original DNA. If this can’t be convincingly portrayed, large scale projects simply won’t get off the ground.

What we do know for sure, is that pizzlies specifically are a product of profound environmental instability. That in itself, surely, is unacceptable.


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