Sonali Kolhatkar reports for Truthdig from Paris. See more of her COP21 coverage here.

The United Nations Climate Change Conference, or COP21, in Paris has been marred by a crackdown on dissent in the wake of the Islamic State attacks on Nov. 13. Among the people hardest hit by the French government's security measures are migrant communities of color, especially in Paris.

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Today, migrant-rights activists from the United States rallied in solidarity with their French counterparts in front of a detention center near Hippodrome de Vincennes. In 2008, that detention center was the site of major protests after a Tunisian man died in custody.

The action was a spirited gathering that featured music, song and large, colorful banners in English and French. Many rallied around the idea that environmental injustice is linked to migration. But there was also a focus on growing Islamophobia -- a particularly crucial issue even in the U.S., where GOP presidential candidate Donald Trump this week called for the banning of Muslims entering the U.S.

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Arturo Trejo, an activist with the Southwest Workers' Union in San Antonio, Texas, attended Wednesday's migrant rights rally. I spoke with him about why he is in Paris and what happened at the gathering today.

Meanwhile, Paris authorities have clearly taken their role as host city to COP21 quite seriously. The city is awash in references to the conference, starting at the Charles de Gaulle Airport. A large and ambitious installation on renewable energy and conservation technologies lines the River Seine. The interactive exhibits are slick, with corporate-style buzzwords. They include eco-toilets, trash compacting and electric vehicles.