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Parisiens did a funny thing on Wednesday. As spring flowers started to peek above the soil and the sun rode higher in the sky, a number of the city dwellers flocked to greet their newest lawnmowers: a small group of shaggy black sheep. As the latest effort in Paris Mayor Bertrand Delanoë's grand plan to make the City of Lights a greener place — the local government's calling the effort "eco-grazing" — four two-foot-tall sheep from the Breton breed will live and, more importantly, eat in a half acre patch of park in the city's 19th Arrondissement, the home of the Conservatoire de Paris, one of Europe's premier music schools. In October, they'll find a warmer clime.

It's honestly a pretty sensible idea. For centuries, if not millennia, grazing animals like sheep and cows have been used both to trim and to fertilize fields. In fact, many of the oldest urban parks were originally populated by farm animals, sometimes just during the day when their owners went into to town to do business. A funny if only marginally related story about in-town grazing comes from Cambridge, Massachusetts, a former suburb of Boston that's now very much a part of the city. Back in the early days of Harvard College, one of the perks of being a professor was that you were allowed to graze your cow in Harvard Yard. Back in 2009, retiring professor Harvey Cox actually exercised this privilege when he brought his cow Faith to school.