U.N. Study: Earth's Health Deteriorating

Growing populations and expanding economic activity have strained the planet's ecosystems over the past half century, a trend that threatens international efforts to combat poverty and disease, a U.N.-sponsored study of the Earth's health warned on Wednesday.

The four-year, $24 million Millennium Ecosystem Assessment found humans have caused heavy damage or depleted portions of the world's farmlands, forests and watercourses.

Unless nations adopt more eco-friendly policies, increased human demands for food, clean water and fuels could speed the disappearance of forests, fish and fresh water reserves and lead to more frequent disease outbreaks over the next 50 years, it warned.