For years, a picture of a bear captured in the Canadian Arctic that is bigger than a polar bear and has the brown-tipped fur of a grizzly has been quietly shared among wildlife biologists. It’s not a camera trick. It’s a grolar bear, the progeny of two species whose ranges were never meant to coincide, brought together by temperatures that have been steadily rising since before the majority of wildlife managers began their careers. Nobody is quite sure how to handle it legally.
This quiet uncertainty is turning into a slow-motion crisis. Animals and plants that have evolved on different paths for millions of years are finding themselves in the same areas, frequently breeding, as global temperatures continue to push species outside of their historical ranges. A common toad and a green toad, two species whose lineages diverged about 20 to 30 million years ago, were seen mating at a high-altitude pond in a regional park in Southern Italy.
This would have seemed unthinkable not too long ago. The breeding schedules of both species had been slightly modified by climate change, narrowing the gap. The majority of the resulting tadpoles had serious deformities. None made it to the metamorphosis stage. The majority of the witnesses were scientists who happened to be in a mountain pond when the small, silent disaster occurred.
In contrast, the law was designed for a world in which species remained stationary. Most nations’ environmental laws, such as the European Habitats Directive and the U.S. Endangered Species Act, are predicated on the idea that species have comparatively stable, distinguishable identities. A species can be classified as either listed or not. Either it is protected or it is not. For a long time, it didn’t really matter that hybrids fell into a gray area that regulators were never quite sure how to handle. It is very important now.
The problem simultaneously runs in two uncomfortable directions. On the one hand, hybridization—a form of genetic erosion in which a more common species gradually absorbs a rarer one—has long been seen as a threat to biodiversity. The wildcats of Europe provide a terrible example of this. There are only a few hundred left in Scotland, and interbreeding with domestic cats poses the biggest threat. To varied degrees, a genetic blend now roams parts of the Highlands. Within a century, wildcats in the Jura mountains of Switzerland may become genetically identical to domestic cats, according to research models. Does the law protect them if that occurs and they continue to resemble wildcats? Does it really matter?
However, hybridization can occasionally be beneficial, and this is where the discussion has become genuinely complex in recent years. Through cross-breeding with Atlantic killifish that had a helpful mutation, the Gulf killifish in the polluted Houston Ship Channel developed resistance to harmful chemicals. Researchers studying coral have demonstrated that some hybrid offspring outperform their parent species in terms of survival at high temperatures. Hybridization can introduce adaptive genetic variation that provides struggling populations with something to work with as the climate changes, according to a 2023 paper reviewing conservation literature. It’s more than just damage. It can be a lifeline at times.
The legal question is genuinely challenging because of this dual nature. In certain instances, laws intended to stop genetic dilution may be obstructing the very mechanism that could enable a species to endure. On the other hand, if hybridization is allowed to continue unchecked, genetic lineages that took tens of millions of years to develop could be silently eliminated. Lawmakers and conservationists seem to be navigating without proper maps.
A more “nuanced” approach, based on the precautionary principle—basically, be cautious, keep a close eye on things, and don’t assume either outcome—has been advocated by some researchers. That makes sense, but it’s actually difficult to incorporate into a regulatory framework that requires precise regulations in order to operate. Definitions are necessary for courts. Categories are necessary for agencies. There is no place for a species that is 60% polar bear and 40% grizzly.
It is becoming more and more obvious that the current framework, which has essentially remained unchanged in its philosophical underpinnings since the 1970s, was not intended for a dynamic world. Due to necessity rather than choice, species are migrating poleward, uphill, and into each other’s territories. The subsequent mixing is not a failure of policy. When the temperature fluctuates, physics and biology do what they do. However, the laws that dictate our response to it were drafted at a time when we still believed that the distribution map of species would essentially stay the same.
That presumption is no longer valid. Somewhere in the Canadian Arctic, the grolar bear is living evidence of that, unaffected by the legal controversy it has sparked.
