Conservation efforts to protect source watersheds are crucial to securing clean, reliable water supplies for large cities, where more than half the world's population lives, a report published by the Nature Conservancy finds. Developed in partnership with the C40 Cities Climate Leadership Group and the International Water Association, the report, Urban Water Blueprint (108 pages, PDF), warns that degradation of water quality caused by nutrients from fertilizer washing into streams and lakes will worsen as more forests are converted into cropland and ranchland and fertilizer use increases. On a more positive note, the study found that in the vast majority of the world's urban source watersheds, at least one of five common strategies — forest protection, reforestation, riparian restoration, best management practices with respect to agriculture, and forest fuel reduction — can significantly reduce run-off sediment and nutrient pollution. Funded by the Ecolab Foundation, the Starwood Hotels and Resorts Worldwide Foundation, and the Rockefeller Foundation's 100 Resilient Cities initiative, the report includes an analysis of the effectiveness of each strategy for five hundred and thirty-four cities around the globe.