Complex sentence: Narwhals are one of the most vulnerable Arctic marine mammals to climate change due to altering sea ice coverage in their environment, especially in their northern wintering grounds such as the Baffin Bay and Davis Strait regions.
Split into simpler sentences: Narwhals are one of the most vulnerable Arctic marine mammals to climate change. One of the aspects that make narwhals vulnerable to climate change is the altering sea ice coverage in their environment, especially in their northern wintering grounds such as the Baffin Bay and Davis Strait regions.