On March 3, two armed men entered the home of Berta Cáceres, an environmental activist in Honduras, and shot her dead. For years, Ms. Cáceres had vigorously opposed the proposed Agua Zarca Dam, to be built on the land of an indigenous people, the Lenca.

Ms. Cáceres was one of 185 environmental activists killed in 16 countries last year, according to a new report published by Global Witness, a nonprofit organization dedicated to exposing environmental abuses. Those murders represent a 59 percent increase over the number murdered in 2014, according to the report, and the highest since Global Witness began compiling data in 2002.

“The environment has emerged as a new battleground for human rights,” said Billy Kyte, a campaign leader at Global Witness and the report’s author.