The enormous value of the region's ecosystems was acknowledged towards the end of the 70s, when attempts were made to protect it. In May 1992, the National Marine Park of Alonnisos and Northern Sporades was founded. It includes all the Northern Sporades except for Skiathos and Skopelos islands.

The Park is not an enclosed area. It is a conservation area of roughly 2,200 km2, probably the largest marine conservation area in the Mediterranean.

Its purpose is to protect the ecosystems and to promote the development in Alonnisos (the only inhabited island in the park) within renewable parameters and without forced intervention.
Since 1990, MOm collaborates with the Hellenic Ministry of Environment, Physical Planning and Public Works, the Ministry of Mercantile Marine, the Ministry of Agriculture, the Prefecture of Magnesia and the Municipality of Alonnisos to conduct regular briefings that inform and sensitize residents and visitors.
The official administrative body of the park was founded in 2003, and includes representatives from all the above bodies and is responsible for managing the park.

Habitat types in the Marine Park
Twenty habitat types have been recorded in the marine park area, and are included in Community Directive 92/43/EEC

1. Posidonia beds. Fikiades (seaweed-like expanses) grow on the sandy sea bed near the shore and are under priority conservation.
2. Reefs. Rocky projections on the sea bed that attract a rich array of marine life.
3. Coastal lagoons. Under priority conservation.
4. Annual vegetation of drift lines.
5. Mediterranean salt meadows (Juncetalia maritimi).
6. Vegetated sea cliffs of the Mediterranean coast with endemic Limonium spp. Sea cliffs (with various species of Limonium growing in crevices) are common in the Northern Sporades
7. Sandbanks which are covered by sea water all the time.
8. Embryonic shifting dunes. Small sand-hills behind beaches.
9. Mediterranean temporary ponds. Seasonal ponds that form only in winter and spring and are priority conservation areas.
10. Arborescent matorral Juniperus spp. Evergreen juniper shrubs grow sparsely on a few slopes of the islands.
11. Thermo-Mediterranean and pre-steppe brush: formation or plant. Communities with Euphorbia dedroides. Large shrubs growing between bays and vertical rocks - they appear only in the central and northern Aegean region.
12. Sarcopoterium spinosum phrygana. Phrygana that are common along the coastline of Southern Greece, but do not exist outside the Eastern Mediterranean.
13. Pseudo-steppe with grasses and annuals of the Thero-Brachypodietea. This rare habitat is under priority conservation.
14. Screes of the Balkan peninsula. These screes are scarce in the region and can be found at the base of cliffs.
15. Calcereous rocky slopes with chasmopliytic vegetation. Rocky slopes are common on several islands and are home to endemic plant species.
16. Caves not open to the public. A precious habitat for bats and cave-dwelling fauna.
17. Submerged or partially submerged sea caves. Nothern Sporades' most valuable asset because it provides refuge to the Mediterranean monk seal.
18. Olea and Ceratonia forests. Fairly common in the area.
19. Quercus ilex forests. Common in the region and significant for the Mediterranean bird species (especially for wintering).
20. Mediterranean pine forests with endemic Mesogean pines including the Pinus mugo and Pinus leucodermis. Common in Alonnisos, but not on the rest of the islands.