Several beaches in France's northwest have been closed due to worries that toxic seaweed, blamed in the deaths of dozens of wild boar, could be a hazard to humans.

The phenomenon occurs when runoff of excess fertilizer enters the ocean, prompting a rapid growth of seaweed that then washes up on the shore. Once on land, it releases toxic gases as it rots.

Environment Minister Nathalie Kosciusko-Morizet ordered the beaches along the coast of Brittany closed several weeks back, but the problem persists.

According to Radio France Internationale, Kosciusko-Morizet argued that farming practices were largely to blame for the excess fertilizer, and that a balance needed to be met between the demands of farming and the demands of tourism.

Have a look at Brittany's green beaches below: