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Earth Day comes right before National Volunteer Week, an annual celebration of North American volunteerism in late April. This fortuitous timing gives environmental nonprofits an opportunity to engage prospective volunteers, especially nonwhites who live in communities exposed to environmental injustices.

But although people of color are more likely than whites to live in polluted places, they are much less likely to volunteer on behalf of these causes than whites. This lack of diversity renders green groups less effective.

As someone who researches environmental volunteerism, I understand that these nonprofits are often responsible for protecting vulnerable communities. They were among the first to demand accountability in 2015, when news of the lead-poisoned water supply in Flint, Michigan, shocked the nation, for example.

With the Trump administration rolling back environmental regulations, these nonprofits need all the help they can get. That makes it more important than ever for them to do a better job of recruiting volunteers of color.

Most U.S. environmental organizations are less diverse than this group of Californian environmental justice leaders (

The number of environmental groups has increased in recent years, growing nearly 20 percent from 11,233 in 2003 to 13,283 in 2013.

Despite this growth, people from communities of color engage in environmental volunteerism at lower rates than whites, according to the Bureau of Labor Statistics. In 2015, for instance, 3.1 percent of white Americans volunteered for green causes, while only 1.6 percent of Latinos and 1 percent of black Americans did so.

This racial divide is unfortunate since environmental injustices often disproportionately affect communities of color. According to a recent national study by researchers at the University of Minnesota, people of color are exposed to deadly airborne pollutants at significantly higher rates than whites. And a recent study by Michigan authorities found that systemic racism helped trigger Flint’s water crisis. More than half of the city’s residents are black.

Why, then, don’t more people of color volunteer for environmental causes? Here are three possible reasons.

First, as the civil rights era wound down in the late 1960s, some people of color feared that environmental advocacy would shift…