Alonissos is the largest of the islands that make up the Marine Park of the Northern Sporades (NMPANS) and is the only inhabited island.  There are no restrictions on human activity on Alonissos and Peristera other than for trawler fishing.

The islands of the Marine Park are home to a number of rare or endangered species of mammals and birds.  The rarest mammal is the Mediterranean Monk Seal which uses the island of Piperi for its breeding ground and hence the island is protected by an exclusion zone of 3 nautical miles.  The other islands of the marine park are home to a variety of rare species of birds such as Audouin's Gulls, Bonelli's Eagles, Eleonora's Falcons and Shags.  The island of Gioura is home to a Wild Goat which is endemic to the island but bordering on extinction.  The Marine Park is also home to a number of varieties of dolphins and whales.  

Summer excursion boats and charter craft visit the sheltered bays and sandy beaches of Kyra Panagia, Peristera, Psathoura and Skantzoura.  Visits to Gioura have now been stopped since the impostition of a 400 metre exclusion zone around the island.  The islands are generally covered with vegetation and have steep rocky coastlines with mountainous interiors.  The exception is Psathoura which is the only volcanic island and where you will find one of the brightest lighthouses in the Aegean.