Activists who have gathered in Paris for this week's international summit on climate change won't let security concerns mute their message. Hundreds of thousands of people were expected to flood the streets of Paris over the weekend for a major march ahead of the United Nations Conference on Climate Change. But authorities canceled the demonstration amid ongoing security concerns following the November 13 terror attacks that killed 130 people. That order didn't stop tens of thousands of boots (and flats…and sandals…and sneakers…and heels) from hitting the ground on Sunday. Activists covered Paris' famed Place de la Republique with shoes — some decorated with notes, and even plants, to serve as a reminder of the masses who would have participated in the march. “What we’re seeing here is an outpouring of determination from Parisians to be heard nonetheless,” Emma Ruby-Sachs of the advocacy group Avaaz told the BBC. “These are shoes from the closets of average citizens decorated with notes from people — there’s even plants, planted in the shoes themselves. And they’ve been installed here as a signal of that determination and as a memorial to that outcry.” The footwear activism was a peaceful contrast to clashes that broke out between police and a number of protesters who defied orders to stay home. More than 200 people were reportedly arrested during those demonstrations. The U.N. climate summit, known as COP21, is bringing together about 150 world leaders. The goal is to reach an agreement on curbing greenhouse-gas emissions.