Grass-roots environmental nonprofits are too often ignored by foundations, says a new report by the National Committee for Responsive Philanthropy.

Foundations give half of the dollars they spend on the environment to national organizations with budgets of $5-million or more, but those charities make up only 2 percent of the environmental groups in the United States, according to the watchdog.

Only 15 percent of environmental grant making helps poor communities, the study found. A smaller share—11 percent—supports grass-roots advocacy and organizing.

The report recommends that foundations contribute 20 percent of their environmental giving to groups working with poor communities and 25 percent to advocacy and organizing.

The report is part of a series analyzing what share of foundation giving supports  grass-roots groups, advocacy efforts, and low-income communities. The National Committee for Responsive Philanthropy advocates that foundations give more money to such work.