The world’s oceans may be turning acidic faster today from human carbon emissions than they did during four major extinctions in the last 300 million years, when natural pulses of carbon sent global temperatures soaring, says a new study. The study is the first of its kind to survey the geologic record for evidence of ocean acidification over this vast time period.

The majestic leatherback turtle is the largest sea turtle in the world, growing to more than 6 feet in length. It is also one of the most threatened. A major new study of migration patterns has identified high-use areas — potential danger zones — in the Pacific Ocean for this critically endangered species. This new understanding could help inform decisions about fishing practices to help reduce further deaths of this fragile species.