epa04412509 A man holds down a large bubble representing carbon as part of the Occupy Wall Street movement in New York, New York, USA, 22 Sept. 2014. Activists gathered in downtown Manhattan to participate in the Flood Wall Street protest ahead of the UN Climate Summit, which commences in the city from Sept. 23. EPA/ANDREW KELLY

Protests are a visible and important way for citizens to express grievances and hold officials to account outside the electoral season. Many climate change activists seem to think that protests can have big consequences.  For example, organizer Bill McKibben suggested that the massive People’s Climate March in September had helped cause the US-China climate announcement of a few weeks ago. He tweeted, “First reaction to US China climate news: We should do more of these big protest-type things, they seem useful.”

But did the People’s Climate March actually cause these policy outcomes? Maybe.  The truth is that it’s really difficult to assess the causal impact of protests.  Many of the same things that drive people out to the streets also influence politicians to take actions in support of the movement’s cause.  When the tide of public opinion shifts to support a movement, for example, we can expect to see both more protest and more favorable policy outcomes.  So are the protests themselves influential, or are they simply a visible manifestation of a process of change that was already underway?

Researchers have tried to solve this puzzle for years.  In a recent paper, Madestam, Shoag, Veuger and Yanagizawa-Drott examine the effect of the 2009 Tea Party Tax Day Rallies.  Employing a clever research design, the authors found that the Tea Party was able to shape policy more in areas where they had previously had bigger initial rallies. In another paper examining environmental protests since the 1960s, Agnone suggests that more pro-environmental legislation was passed when protest made pro-environmental public opinion more relevant to legislators.

These papers suggest that protests do not simply reflect pre-existing shifts in public opinion. They help to build and intensify individual policy preferences. This is clear from examining activism on climate change.  Protests can sometimes serve as a threat: as when activists engage in confrontational protests on the Keystone XL Pipeline to try to garner direct policy concessions from politicians. But protests can also build movements and reshape public opinion around issues, feeding back into the policy process indirectly.

The People’s Climate March is plausibly an example of this second kind of organizing.  Officially, the the protest set out to influence world leaders visiting New York for the UN Climate Summit by making the strength of public support for climate action visible in the streets. But the most consequential part of the march was what happened before the protests: the outreach and organizing that diversified the movement and connected climate change to other issues that individuals already feel passionate about.

As I document in my forthcoming book, climate activists have been trying to broaden and diversify their movement over the past several years by talking more about climate change as a “justice” issue than an “environmental” issue.  In doing so, they’ve been able to mobilize a more diverse set of participants, including religious leaders, labor union members, students, indigenous peoples, and frontline communities most affected by climate change. This strategy of change emphasizes building power from the ground-up instead of just focusing on policy outcomes. As one organizer from Friends of the Earth explained it to me in 2013:

“A lot of NGOs were working for a long time with a frame that was very technical and demotivating for a lot of people.  And it was really based on a theory of change that “if we change our governments, we can change the system.” Climate justice is much bigger than that. Climate justice helps us build the movement.”

The language of climate justice broadened the movement and helped it grow much larger, culminating in the turnout of over 300,000 people at the march in September.

What does examining this case tell us about how protest might influence policy?  One thing the People’s Climate March illustrates is that changes in public opinion can be constructed by organizers in order to expand and broaden participation.  The way we talk about issues affects who participates and how much they participate. Because being in the streets with others is often a powerful experience, social movement participation can make individual preferences stronger, create new kinds of collective identities, and shape the course of people’s lives.

It may be harder to track how these kinds of organizational and individual-level changes might ultimately shape policy.  But understanding how bringing people to the streets can support broader movement-building objectives helps us to grasp why many organizers continue to believe in the power of protest and why we’re likely to see continued reliance on this strategy of social change.

Jennifer Hadden is an Assistant Professor in the Department of Government and Politics at the University of Maryland. Her research concerns social movements, climate change, and international relations. Her book Networks in Contention: The Divisive Politics of Climate Change is forthcoming at Cambridge University Press.

This post is part of the Scholars Strategy Network series on civic engagement between elections.

See also:

Jenny Oser, Marc Hooghe and Sofie Marien, New technologies encourage women, but not poor people, to participate in politics

Dave Karpf, The reason why your inbox is flooded with political e-mail.

Peter Levine, Social media hasn’t boosted young voter turnout.

Edward Walker, How business funded the anti-soda tax coalition.

Hahrie Han and Elizabeth McKenna, Engaging voters can kickstart community activism.