Lastovo and its archipelago are made of Jurassic and Cretaceous sediments made primarily by dolomite, dolomite limestone, and pure limestone.
The highest peak of the island of Lastovo, Hum (417 m), is the most beautiful observation point on the island; it boasts a view of the variety of the landscape, with its rolling hills, deep bays and fields, and also an infinite view of the sea and the islands. The peaks of Mali Hum (415 m) and Pleševo brdo (400 m) are somewhat lower.
Morphologically, the series of separate forested hills and karst bays – fields is noteworthy (the largest fields are Vinopolje, Lokavje and Prgovo), which were created in impermeable zones of dolomite or semi-permeable dolomitic limestone.
The karst composition of Lastovo was favourable for the creation of caves. The most popular cave is the Rača cave in the south-eastern park of the island, which was protected as a geo-morphological monument of nature and an archaeological site in 1965, and Medjedina, once the habitat of the Mediterranean monk seal, which is today known for large populations of bats.
Biology - land
The Lastovo islands are one of the richest and most preserved botanical areas in the Mediterranean.
The make-up of the vegetation of the island of Lastovo has been determined by the offshore remoteness, plenty of sunshine and night humidity and special and deep Lastovo soil. Out of 810 recognized species, you can meet everything from endangered species, otherwise extinct species, endemic and stenoendemic species.
In addition to bjeličasta gromotulja (Aurinia leucadea) other botanic rarities are a special rarity of the Croatian vegetation, trsovez (Ampelodesmos mauretanica), which can be found only on Lastovo as a stenoendemic species and the legally protected species of dalmatinski kozlinac (Biserrula pelecinus ssp. dalmatica).
The flora of the island of Sušac was created due to the lack of water in the sparse ground and constant exposure to strong southern wind. This specific vegetation has 278 plant species; among eight endemic species, we can point out sušačka vrzina (Brassica cazzae), which grows in the cracks of coastal rocks.
Around 70% of the islands is covered in woods, which makes Lastovo the woodiest Croatian island next to Mljet. It is covered mainly in underbrush – the most beautiful tree is planika (Arbutus unedo), but the most important cover is crnika (Quercus ilex), and the forests of the Aleppo pine (Pinus halepensis). Under the forest cover, you can find mushrooms.
The Lastovo houses are decorated by Mediterranean plants: almonds, lemons, oranges, palm trees and carob. This climate is also favourable for the growth of medicinal herbs, such as sage, mint, yarrow, rosemary, lavender, fennel, and chamomile. Of the cultivated plants, the most widespread ones are the vine and olive.
The island’s animal world is also very rich. 175 species of vertebrates have been registered so far, 71 of which are endangered on a national level, while 37 species are endangered on a European level.
The caves of Lastovo are the home to bats, which they use as shelters or places for breeding, such as Medjedina, which is the home to 3 endangered bat species – the Mediterranean horseshoe bat (Rhinolopus euryale), Geoffroy’s bat (Myotis emarginatus), and the greater horseshoe bat (Rhinolophus ferrumequinum).
The Lastovo archipelago is an important resting place for many migratory birds, and is the nesting place of the Mediterranean shearwater (Puffinus yelkouan) and the Scopoli’s shearwater (Calonectris diomedea). The eastern groups of Lastovnjaci and Vrhovnjaci is the nesting place of around 70 % of the Croatian population of the globally endangered Audouin’s gull (Larus audouinii). The cliffs of Struga (Velike stijene) is the nesting place of the rare Eleonora’s falcon (Falco eleonorae).
It is interesting to note that there are no venomous snakes on the islands, and the only snake species is the Caspian whipsnake (Dolichophis caspius). The Lastovo archipelago is also the habitat of stenoendemic lizards – the Italian wall lizard (Podarcis sicula adriatica) and the Dalmatian wall lizard (Podarcis melisellensis n. ssp.).
The area is rich in micro-fauna, especially insects, spiders and snails.
Biology - sea
The richness of the archipelago’s underwater is evidenced by 248 species of the marine flora. This number in such a small area is equivalent to the number from the wide surface of the central and southern Adriatic. In this area there is a seasonal flow of nutrients from the deep Adriatic; this phenomenon makes it possible to for marine life to flourish.
The rocky floor is covered in photophilic algae, while the shallow coastal seabeds are covered in the endangered and protected Posidonia oceanica. This species is a very important hatchery and shelter for many marine species. The hidden harbour is an extremely rare habitat of the green alga Caulerpa prolifera, the only indigenous caulerpa in the Adriatic.
Thanks to the abundance and variety of the zooplankton, the underwater world of the Park is rich in corals, sponges, molluscs, Bryozoa, echinoderms, crabs and many other species, so the chains in the underwater life chain are very strong. 330 species of invertebrates have been registered so far, 20 of which are on the endangered species list.
The clusters of gold coral (Gerardia savaglia), red coral (Corallium rubrum) and the endemic Hvar coral (Madracis pharensis) are especially beautiful.
In the zone of tidal oscillation, there are many different marine snails, and limpets. They are followed by sea scallops, octopus, and cuttlefish. The trademark of the rock bottom are colonies of lobsters, kuke (sovice) and crabs. This is also the habitat of rare species of snails – the Triton’s trumpet (Charonia tritonis sequenza), the zoned mitre (Mitra zonata), and the giant tun (Tonna galea).
The species of fish characteristic for this are the black scorpionfish, the red scorpionfish, the dusky grouper, the dentex, the black seabream, the striped red mullet, the forkbeard, the East Atlantic peacock wrasse, the Muraena, the European conger and others. There is also tuna, the greater amberjack and the swordfish.
The open waters of this area are the home of several species of dolphins – the short-beaked common dolphin (Delphinus delphis), the common bottlenose dolphin (Tursiops truncatus), and Risso’s dolphin (Grampus griseus), as well as turtles – the loggerhead sea turtle (Caretta caretta) and the green sea turtle (Chelonia mydas).
The secluded cliffs of the Medjedina caves were previously the home of the Mediterranean monk seal (Monachus monachus); sporadic meetings of the island people with the animals stokes the hope in its return.
The ecological network of the Republic of Croatia represents the areas of the EU ecological network Natura 2000 and it has significant conservation areas for birds and conservation areas important for species and habitat types.
The ecological network in the area of the municipality of Lastovo and the “Lastovo Islands” Nature Park covers areas important for wild taxa and habitat types and internationally important bird areas.
Although the Adriatic is equally wide throughout its length and the flight of birds goes in a wide front, there appear to be parts where the flight is more intense. The Lastovo-Palagruža-Pelješac corridor is important for large striking flocks of non-seabird species that migrate over the Adriatic. The data indicates that this is an area of the so called “bottleneck” for the flight of some species of birds of prey and cranes. During the flight, the birds are concentrated over the peninsula Gargano (Italy) -Palagruža-Lastovo-Pelješac-Rilić. For example, this is a resting spot for more than 700 European honey buzzards and over a thousand cranes. There are also many well-known and widespread coastal bird species: grebes, shags, seagulls, mergansers, and terns. In addition to this, seabird species are also characteristic for this area. For the one the seabird species in the Procellariidae family, yelkouan shearwater (Puffinus yelkouan), it is certain that they nest on the isle of Zaklopatica in the Lastovo archipelago, and today the total population is estimated to less than 100 couples.
The WWF (World Wildlife Fund) has declared the Nature Park as one of the ten last treasuries of biodiversity in the Mediterranean Sea; this has been greatly contributed by the diversity of marine habitats and taxa. In particular, the coraligenic community and community of meadows of posidonia housing numerous taxa are especially noteworthy, and their features offer great services to the ecosystem – hatcheries, sea basin stabilization, oxygen production, etc.