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3. CANARY ISLANDS. PARKING NEAR THE ISLAND OF TENERIFE

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Gilbert Islands, Marshall Islands, neutralization of Truk base, first attacks on the Marianas - June 1943 - April 1944

Gilbert Islands, Marshall Islands, neutralization of Truk base, first attacks on the Mariana Islands - June 1943 - April 1944

Oceania is the name of the largest cluster of large and small islands on our planet in the western and central Pacific Ocean. The islands of Oceania occupy about 1.3 million square kilometers of the Earth's surface and there are almost 7 thousand of them, large and small.

Regions of the islands of Oceania

Traditionally, the islands of Oceania are divided by geographers, historians and ethnographers into three groups: Melanesia with the largest island of New Guinea, Micronesia, Polynesia with the second largest island of Oceania, New Zealand.

The region of the islands of Oceania Melanesia ("black island")

Melanesia is located in the west of Oceania and, in addition to New Guinea, it includes the Bismarck and Louisiade archipelagos, as well as the islands of D "Anrtkastro, the Santa Cruz Islands, Solomon islands, New Herbid Islands, New Caledonia, Fiji Islands, Loyalty and several others.

The main part of the territory of Melanesia falls on the island of New Guinea. He owns 829 of the 969 thousand square kilometers occupied by this area of ​​the islands of Oceania.

Region of the islands of Oceania Polynesia ("multi-island")

Polynesia stretched from the southwest to the east of Oceania. The largest islands of Polynesia are New Zealand, Hawaii, Tonga, Samoa, Wallis, Tokelau, Horn, Cook, Tuvalu, Tubuai, Societies, the Marquesas Islands and Easter Island.

265 thousand square kilometers of the total area of ​​Polynesia falls on New Zealand, 17 thousand - to the Hawaiian Islands and 9 thousand - to all the rest.

Ocean Islands Region of Micronesia ("small islands")

Micronesia is located in the northwest of Oceania. total area its islands are only 2.6 thousand square kilometers, but these tiny islands are scattered over an ocean area of ​​\u200b\u200babout 14 million square kilometers.

The main island groups of Micronesia are the Marshall, Caroline and Mariana Islands, as well as the Gilbert Islands.

Islands of Oceania by type of origin

The islands of Oceania differ in their origin and on this basis they are usually divided into four types: volcanic, coral or atoll (biogenic), continental, and also geosynclinal.

Volcanic islands of Oceania

The volcanic islands of Oceania are the peaks of dormant or active underwater volcanoes. Among them there are islands ranging from ten square kilometers to several thousand and they are the main type of islands in Oceania.

The most famous of the volcanic islands are the Hawaiian Islands, Easter Island, Tahiti and Samoa.

Coral islands of Oceania (biogenic)

Entire colonies of small marine animals - corals - usually settle in the oceanic shallow water. For centuries, when corals die, their skeletons cover the bottom of the ocean, are pressed and form a rock. Over time, above the surface of the water appear Coral reefs and entire islands, and if coral deposits occurred along the contour of the vent underwater volcano, then atolls appear - coral islands with a lagoon in the center.

There are hundreds of coral islands (atolls) in Oceania, both single and forming entire archipelagos. These are the Caroline, Mariana, Marshall Islands, as well as the Gilbert and Tuamotu Islands. The largest atoll in Oceania is Kwajalein. The area of ​​​​its territory is 2.3 thousand square kilometers (including the area of ​​​​the lagoon) and it belongs to the Marshall Islands archipelago.

Mainland islands of Oceania

The mainland islands of Oceania were once part of the mainland and became islands as a result of the movement of the earth's crust. So New Guinea Australia is separated from the mainland only by a strait, the bottom of which until recently was dry land, and New Zealand is part of the huge mainland that once existed, which included both Australia and Antarctica.

The mainland islands of Oceania account for 90% of its territory. They have lowlands, and mountain systems, and extended mountain plateaus.

general characteristics

The biotas of the islands of the seas and oceans are extremely diverse. Closely related to the conditions of formation of the islands themselves, they, however, do not have a single feature that would be characteristic of all the islands without exception. The diversity of the island's biota depends on its origin, age, size, distance from the mainland and its natural conditions.

According to their origin, islands in the seas and oceans are divided into two main groups - continental and oceanic. .

1. Continental represent a part of the continent that separated in one or another geological epoch. They protrude above the water level within the underwater margin of the continents and are usually composed of bedrock (Great Britain, Greenland, Madagascar, New Zealand, New Caledonia, Hawaiian, etc.). Small ones can be formed as a result of the accumulative activity of waves and surf.

2. Oceanic islands are distributed within the ocean floor and on mid-ocean ridges. These include coral (atolls and reefs) and volcanic islands (Galapagos, Kerguelen, Mascarene, Canary, Easter, etc.).

Between these two groups of islands, continental and oceanic, there are intermediate forms - geosynclinal islands, or islands of the transition zone and island arcs. They differ greatest variety natural conditions and have a more complex structure of landscapes - from flat to mountainous areas. As a rule, all geosynclinal islands form into archipelagos or form island arcs (Great Sunda, Philippine, Japanese, etc.).

The complexity of the ecosystems of the islands can be low, including biogenic (atolls, reefs and mangroves) and shelf, and high (volcanic, geosynclinal and continental slope, or shelf). high islands, in turn, may have a weakly or well-defined altitudinal zonality.

The conditions for the formation of biota on continental and oceanic islands are completely different.

1. The mainland islands separated from the continents with the species diversity of vegetation and animal population that was inherent in this part of the continent.

2. Oceanic islands were inhabited only by organisms capable of crossing large expanses of water. In the first case, the type of biota formation can be defined as relic , in the second - as an immigration .

Biomes of mainland islands

On islands of continental origin, the biota gradually becomes depleted over time due to the extinction of some forms and even species. The extinction of a species can be explained by its small numbers at the time of the separation of the island from the mainland, which does not ensure a long existence in conditions of isolation. Moreover, the death of the species inherited by the island is not compensated by the appearance of immigrants who enter the island, as a rule, in a limited number of individuals and do not always survive.

The gradual extinction of species on the islands can be judged from the fact that small islands of continental origin, in contrast to large ones, have almost purely oceanic fauna. So, among the Pearl Islands on big island Rey is inhabited by about 1/3 of continental species, and small island Condator - only 1/10 (Voronov, 1987). If two islands of different sizes separated from the mainland at the same time, then the original biota can be almost completely preserved on the larger one and completely or partially disappear on the smaller one.

Features of the biota of the mainland islands

1. Isolation and remoteness from the mainland determine the high endemism of flora and fauna. How ancient island, the more endemic species and forms. For example, species endemism of the flora of New Zealand, New Caledonia, Hawaiian Islands reaches 70-80%. At a lesser distance from the mainland (the islands of Great Britain, Ireland, Japan, Sri Lanka), endemism is less pronounced.

2. On the islands, deviations are often observed in the appearance of certain groups of animals. For example, large mammals are usually smaller than on the mainland (ponies, Philippine buffalo, etc.). In birds and reptiles, on the contrary, island gigantism is expressed (lizards on Komodo Island, turtles on Galapagos Islands). The reason for this phenomenon has not yet been elucidated.

3. Often the islands are characterized by flightless birds and insects. The origin of flightless birds is associated with the absence of mammals on the islands that could exterminate them. In the selection of flightless insects, their drift by wind and hurricanes into the ocean played an important role. For many species of flying insects, an equilibrium is established between the number of individuals blown away by the wind and the number of individuals brought to the island, provided that the island is part of an archipelago.

4. In their distribution, the biocenoses of the islands follow the same zonal patterns as the communities of the continents. However, their structure and energy connections are simpler with a smaller species composition. Just on big islands With mountain systems(Madagascar, New Zealand, Cuba, Great Britain, etc.) the vegetation cover and animal population are no less complex than on adjacent continents. On islands with a simplified landscape characteristic, the communities are more uniform, and the depletion of the species composition is more significant.

Biomes of oceanic islands

On islands of oceanic origin, communities arise on the products of volcanic activity or coral limestones. The flora and fauna of these islands is entirely immigrant, but may be older than the islands themselves.

Features of the biota of oceanic islands

1. The penetration of species from the mainland to one or another island is facilitated by the so-called "land bridges" and by a chain of islands of volcanic or other origin. On some of these islands, the species may have had a temporary home and migrated to the newly formed island as a relic that arose as a result of extinction in neighboring land areas. Thus, the possibility of an element of relict origin of flora and fauna on the islands of oceanic origin is not excluded.

2. The transfer of organisms through body of water for each individual is random. With long-term existence migration process this transfer acquires a certain statistical probability. So, when crossing a space 100 miles wide, only one individual out of a thousand survives, the next 100 miles - again one individual out of a thousand, and so on. The chance of reaching an island located 200 miles from the source of migration is one in a million.

3. The most common ways organisms colonize islands are hydrochory ( sea ​​currents), anemochory (winds, storms, and hurricanes), and zoochory (transport by birds). In the colonization of the islands by plants and animals, man plays an important role (anthropochory).

4. Mostly birds can actively populate the islands, but this process is restrained by the “nesting conservatism” of the birds themselves. Mature plants washed ashore by waves, as a rule, rarely take root. Epiphytes that are on the trunks survive. Spores and light seeds are transported by wind over long distances, and therefore, for example, ferns on the islands are widespread. Insects generally do not tolerate salt water well and colonize the islands if they are carried by wind or birds. perish in sea ​​water amphibians, reptiles and freshwater fish. Of the reptiles on the islands, only geckos and skinks are common. Ultimately, death in sea water leads to a rather poor species composition of these groups of animals. Yes, in South America there are many amphibians, and on the neighboring Galapagos there are neither frogs nor salamanders, there are no bird species characteristic of the mainland, and from land mammals one genus of bats, rats and a rodent resembling a hamster are represented.

5. Great importance in the settlement of the island by organisms carried by the wind and, to a lesser extent, water, has its "trapping angle" - the location of the island in relation to the flow of migrants. So, if the island is located perpendicular to the flow of migrants, then the probability that the migrant will end up on the island is greater.

The flora of the islands of oceanic origin is characterized by a small number of species composition. Their fauna lacks mammals, amphibians and snakes.

6. The process of speciation on oceanic islands proceeds faster than on the mainland and continents, since, as a rule, a small population of a species with a depleted gene pool is formed on oceanic islands. In addition, this local small population is in geographical isolation. As a result, on different islands, differences arise in the set of genes of the same species, leading to the emergence of intraspecific forms on each island, and subsequently species. In this case, the unfilled ecological niches are also of great importance.

As evidence that reliably confirms the originality of speciation on islands of oceanic origin, one can cite finches living in the Galapagos.

C. Darwin in his diary "A naturalist's journey around the world on the ship" Beagle "" noted that natural history of these islands is highly interesting and well worthy of attention. Most of the organisms living here are natives, not found elsewhere. This "satellite of America", separated from the mainland by space open ocean at 500 - 600 miles, received a few random colonists from the continent. Obviously, one species of finch came to the Galapagos, eating its own food. Finches that did not have enough food died or switched to other food. So, they learned to catch insects, pull out larvae from cracks in tree trunks, crack nuts, eat plant leaves, etc. Ultimately, natural selection led to the formation of specialized forms that filled all the ecological niches on the island intended for songbirds. In the Galapagos, there are 3 genera, 13 species and 37 island forms of finches: large, medium and small ground finches, cactus, thick-billed arboreal, woodpecker, parrot, coconut, mangrove, warbler, etc. Interestingly, the Darwin woodpecker finch, which does not have a long tongue, uses a cactus needle to get an insect from under the bark of a tree.

Quite exotic representatives of the endemic fauna also live on the Galapagos Islands: giant tortoises, ancient marine and terrestrial iguanas, sea lions, lava snakes, flightless cormorants and the Galapagos penguin. Most representatives of the biota of the islands have relatives on the South American continent.

7. Characteristic biota of the islands - a constant "delivery" of settlers. Species that arrived on the island earlier have an undeniable advantage over ecologically close species that arrived on the island later. The first settlers have more time to reproduce and increase in numbers in the absence of competition or the presence of weaker competition.

8. Each species can naturalize on the island only under the following three conditions:

– successful passage of ecesis (a full development cycle from the appearance on the island to the bringing of viable offspring, inclusive);

– survival in competition with species that previously settled the island;

- adaptation to new conditions of existence.

Stages of species adaptation

A) Already at the stage of ecesis, the formation of a community begins, which consists in the adaptation of organisms to living together.

b) At the next stage, the stage of complex grouping, vegetation with several tiers is formed. At the same time, tall plants protect the lower ones from excess sunlight, wind and salt spray. At the same time, the processes of soil formation are activated.

V) At the final stage, despite the absence of many groups of plants and animals characteristic of the land, a biocenosis is established on the islands of oceanic origin. However, the food chains in it are shortened (usually 2–3, less often 4 links). The poverty of the species floristic composition leads to a low diversity of herbivorous animals and the monotony of predators with their low abundance.

Many representatives of the animal population have a connection with the ocean, going through one or more of their stages of development in it or getting food in the aquatic environment.

9. Insular biotas are characterized by a process of cosmopolitanization, caused by the fact that animals and plants that most successfully overcame oceanic spaces inhabited many islands and are found even in several climatic zones and belts. Most cosmopolitans are on low-lying atolls with the most homogeneous ecological conditions and the lowest species diversity of biota. Paradoxically, cosmopolitanization island biota contribute scientists transporting animals and plants from one island to another.

10. The limited number of populations of the island biota and its isolation lead to the rapid extinction of many species due to direct extermination by humans and violation of habitat conditions. This is how the Steler cow (Commander Islands), the wingless guillemot (Newfoundland), the moa (New Zealand), the dodo (Mauritius), etc., died out. The Javanese and Sumatran rhinos, the Ceylon elephant, Galapagos tortoises and other representatives of a peculiar island biota.

11. The most catastrophic for the flora and fauna of many islands are the deliberate or accidental importation of goats, pigs, dogs, cats, rats, house mice and other synanthropic species, as well as unsuccessful attempts to acclimatize animals - objects of hunting. The introduction of European red deer to New Zealand led to the destruction of forests over a large area. In addition, the possum (herbivorous marsupial) brought from Australia to this archipelago destroyed forests in many areas. Pigs exterminated kiwi, owl parrot and tuatara, which survived only on adjacent small islands. The flora of Saint Helena and Kermadec suffered irreparable losses as a result of the importation of goats.

Unfortunately, there are many examples of senseless destruction of both island ecosystems and representatives of their organic world. In just a few millennia of the development of agriculture and centuries of industrial development, man has made noticeable changes in the biological values ​​of the Earth created by nature over millions of years.

MAINLAND ISLANDS

MAINLAND ISLANDS

Land areas that once formed part of the continents, then separated from the latter. At the same time, the continents themselves either still exist, or have long disappeared.

Samoilov K.I. Marine dictionary. - M.-L.: State Naval Publishing House of the NKVMF of the USSR, 1941

mainland islands

land areas separated from continents as a result of geological or hydrological processes.

Edwart. Explanatory Naval Dictionary, 2010

See what "MAINLAND ISLANDS" is in other dictionaries:

Areas of the mainland that have separated from it due to abrasion or the sinking of part of the land below sea level. To M. o. include naib. major islands of the world: Greenland, Kalimantan, Madagascar ... Natural science. encyclopedic Dictionary

Land areas surrounded on all sides by the waters of the oceans, seas, lakes, rivers. They differ from the mainland in relatively small sizes. There are single islands and their groups (archipelagos). Islands in the oceans and seas are divided into mainland ... ... encyclopedic Dictionary

Land areas surrounded on all sides by the waters of the oceans, seas, lakes, rivers. They differ from the mainland in relatively small sizes. There are single islands and their groups (archipelagos). Islands in the oceans and seas are divided into mainland ... ... Big Encyclopedic Dictionary

- (Islands) small parts of the land compared to the continents, surrounded by the sea on all sides. By origin, the islands are divided into mainland, i.e., separated parts of the land, and original, never connected to the mainland, alluvial and oceanic ... ... Marine Dictionary

Land areas surrounded on all sides by the waters of oceans, seas, lakes or rivers. In the seas and oceans, there are single islands and groups (archipelagos). By origin, they are divided into continental (separated from the continents) and oceanic ... ... Marine Dictionary

Land areas surrounded on all sides by the waters of the ocean, sea, lake or river. They differ from the mainland in relatively small sizes. There are single O. and groups of O. Archipelagos. O. in the oceans and seas are divided into continental, ... ... Great Soviet Encyclopedia

O. are called relatively small areas of land, surrounded on all sides by water. They differ from the continents only in size, but the difference between the two is very conditional, since the ratio between the sizes of the penultimate largest ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron Encyclopedic reference book "Latin America"