Authorities are fed-up with tourists to Florida's islands leaving their poo behind

A pristine island estuary in Florida is under threat by visitors who've been rudely leaving their, erm, number-twos behind on the beach, according to authorities.

Florida's Indian River Lagoon is home to thousands of different plant types and hundreds of marine and land species, but human poo is destroying the local habitat.

Tourists are now being issued with waste bags, in the hopes that they'll take their poo with them when they leave.

The waste can't be broken down, according to Emily Dark, an environmental specialist for the Florida Department of Environmental Protection.

"There is a major problem on the spoil islands with improper disposal of human waste," she told Treasure Coast Newspaper.

With no public toilet facilities available, the issue of human waste on the island's pristine beaches have become a major environmental problem, made worst when the area experiences rainfall and faeces seep into the lagoons.

Waste bags have been provided by sign-posted dispensing stations around the island.

These "WAG bags" are lined with a gel compound, similar to cat litter, which enables them to break down human waste, absorb moisture and reduce any nasty smells.

The island also has no bins, with visitors expected to take their rubbish with them, and any stray rubbish left to volunteers to remove.

Unlike national parks with regular soil, the islands are largely formed from sand and limestone, materials which can't decompose poo as regular soil would.

Even poo that is buried won't be able to decompose, and will remain on the island.