Navajo President Joe Shirley Jr. and Hopi lawmakers say environmentalists’ efforts could hurt the tribes’ struggling economies by slowing or stopping coal mining.

Shirley said Wednesday that he will stand in solidarity with the Hopi Tribe, and joined Hopi lawmakers in encouraging other tribes to re-evaluate their relationships with environmentalists.

Environmentalists have waged a campaign against coal as an energy source, in favor of renewable energy such as wind and solar. But the Navajo and Hopi long have depended on coal revenues to fund their governments and pay the salaries of tribal employees on reservations where half the work force is unemployed.