1 . Endangered polar bears are breeding (繁殖) with grizzly bears (灰熊), creating “pizzly” bears, which is being driven by climate change, scientists say.
As the world warms and Arctic sea ice thins, starving polar bears are being forced ever further south, where they meet grizzlies, whose ranges are expanding northwards. And with that growing contact between the two come increasing hybrids (杂交种).
With characteristics that could give the hybrids an advantage in warming northern habitats, some scientists guess that they could be here to stay. “Usually, hybrids aren’t better suited to their environments than their parents, but these hybrids are able to search for a broader range of food sources,” Larisa DeSantis, an associate professor of biological sciences at Vanderbilt University, told Live Science.
The rise of “pizzly” bears appears with polar bears’ decline: their numbers are estimated to decrease by more than 30% in the next 30 years. This sudden fall is linked partly to “pizzly” bears taking up polar bears’ ranges, where they outcompete them, but also to polar bears’ highly specialized diets.
“Polar bears mainly consumed soft foods even during the Medieval Warm Period, a previous period of rapid warming,” DeSantis said, referring to fat meals such as seals. “Although all of these starving polar bears are trying to find alternative food sources, like seabird eggs, it could be a tipping point for their survival.” Actually, the calories they gain from these sources do not balance out those they burn from searching for them. This could result in a habitat ready for the hybrids to move in and take over, leading to a loss in biodiversity if polar bears are replaced.
“We’re having massive impacts with climate change on species,” DeSantis said. “The polar bear is telling us how bad things are. In some sense, “pizzly” bears could be a sad but necessary compromise given current warming trends.”
1. Why do polar bears move further south?| A．To create hybrids. | B．To expand territory. |
| C．To relieve hunger. | D．To contact grizzlies. |
| A．Broader habitats. | B．More food options. |
| C．Climate preference. | D．Improved breeding ability. |
| A．A rare chance. | B．A critical stage. |
| C．A positive factor. | D．A constant change. |
| A．Polar bears are changing diets for climate change. |
| B．Polar bears have already adjusted to climate change. |
| C．“Pizzly” bears are on the rise because of global warming. |
| D．“Pizzly”bears have replaced polar bears for global warming. |
The awful night rolled slowly away, and the dawn greyly broke on THE LAST DAY OF POMPEII! The crowd looked upwards, and saw, with unspeakable fear, a huge cloud
The cries of women broke out; the man looked at each other, silent. At that moment, they felt the earth shaking
Each turned
