Indonesia

Papua New Guinea has 841 living languages within its borders — more than any other country on Earth, and more than 11 percent of all languages currently spoken by anyone anywhere. Indonesia follows with 721 languages, Nigeria with 538, and India with 459. The top five countries alone contain nearly half of the world's approximately 7,000 living languages. This ranking uses Ethnologue 27th edition data with cross-reference from the UNESCO Atlas of the World's Languages in Danger.

Nauru has the world's highest smoking rate — 52% of adults smoke. China has more smokers than any country: 300 million people. Smoking kills 8 million people per year — more than any other preventable cause. Yet tobacco use is rising in low-income countries as it falls in wealthy ones.

Australia's Great Barrier Reef is the world's largest coral structure at 348,000 km². Indonesia has the most coral biodiversity. But 50% of the world's coral reefs have died since 1950 — bleaching events driven by ocean warming are accelerating. Here's the full coral reef ranking and the scale of the crisis.