北極熊は極地の氷原に住んでいるのだが、生息地を失い、絶滅するであろう。

、、。

Polar bears live on the polar ice fields, but they're losing their habitat and will likely go extinct.

Literal

Polar-bear [topic-は] polar-region [of-の] ice-field [in-に] living-is [but-のだが], habitat [object-を] lose-and, go-extinct probably.

Vocabulary-rich sentence. 北極熊 ('polar bear') — literally 'arctic bear.' 極地 ('polar regions'). 氷原 ('ice field') — 氷 ('ice') + 原 ('field, plain'). 生息地 ('habitat') — 生息 ('living, inhabiting') + 地 ('place'). 絶滅する ('to go extinct'). であろう is the formal/literary equivalent of だろう — 'probably, will likely.' An ecological concern statement with elevated register.