Island Biodiversity with special reference to Andaman & Nicobar Islands Dr. Alok Saxena, IFS dr_aloksaxena@rediffmail.com
Islands are natural textbooks that reveal to us how life has developed on Earth -William H. Amos
Fast Facts about Islands Islands cover about 3% of the world s surface yet harbour a disproportional amount of biodiversity, and endemic species in particular One third of the world s conservation hotspots are islands Of 724 recorded animal extinctions in the last 400 years about half were island species At least 90% of bird species that have become extinct in that period were islanddwellers 12 of the 18 centres of marine endemism are around islands Seven of the 10 coral reef hotspots surround islands Many island species are endemic Over 90% of Hawaiian species are endemic 50% of all plants, mammals, birds, reptiles and amphibians in Mauritius are endemic Islands demonstrate the impacts of climate change and invasive species far before they are visible on larger land masses Islands are the most damaged by climate change without having contributed to it in any significant manner Small island developing States are among those facing the most alarming rate of biodiversity loss.
What is an Island An island is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot or holm. A grouping of geographically or geologically related islands is called an archipelago.
What is an Island The Millennium Ecosystem Assessment, for example, defines islands as lands isolated by surrounding water and with a high proportion of coast to hinterland ; stipulates that they must be populated, separated from the mainland by a distance of at least two kilometres, and measure between 0.15 square kilometres and the size of Greenland (2.2 million square kilometres).
Types of Islands There are two main types of islands: continental islands and oceanic islands. There are also artificial islands. There is no standard of size which distinguishes islands from islets and continents.
A. Continental Islands: Formed on continent; may have formerly been connected to mainland by land bridge: Current Sea Level Island Continent Submerged Land Bridge Continental Shelf Former Sea Level
Cliff at coast
Tombolo Shodo Island, Japan
Examples of Continental Islands 1. British Isles 2. California Channel Islands 3. Block Island, Nantucket, Martha s Vineyard
B. Oceanic Islands: Never connected to continent; usually formed by volcanic activity and isolated from continent by deep ocean. Current Sea Level Oceanic Island Continental Shelf Former Sea Level Undersea Volcano Sea Floor
Examples of Oceanic Islands Iceland Japan Aleutians Bermuda Caribbean Islands Hawaiian Islands South Pacific Atolls Et al.
Many Caribbean islands were formed by volcanic activity at subduction zone.
Origin of Islands Continental Drift
Continental Drift
Continental Drift
Plate Tectonics
Life on Islands
Darwin and The Origin of Species
The route of The H.M.S. Beagle
Darwin and the Galapagos
Some unique features of Island biodiversity Endemism Gigantism and also dwarfism Flightlessness Fearlessness Abundance
Factors that Influence Island Communities Degree of isolation (distance to nearest neighbor, and mainland) Length of isolation (time) Size of island (larger area usually facilitates greater diversity) Climate (tropical versus arctic, humid versus arid, etc.) Location relative to ocean currents (influences nutrient, fish, bird, and seed flow patterns) Initial plant and animal composition if previously attached to a larger land mass (e.g., marsupials, primates, etc.) The species composition of earliest arrivals (if always isolated) Serendipity (the impacts of chance arrivals) Human activity
Island Biogeography Model Given by Robert McArthur and E.O. Wilson (1967) Number of Species on an Island depends on Area of Island Distance from species source (Mainland)
Life on Island- The case of Krakatau
The Krakatoa volcanoes erupted and exploded in 1883, causing massive tsunamis and killing at least 36,417 people, while simultaneously destroying over two-thirds of Krakatoa island. The explosion is considered to be the loudest sound ever heard in modern history, with reports of it being heard up to 3,000 miles (4,800 km) from its point of origin. In 1927 a new island, Anak Krakatau, or "Child of Krakatoa", emerged from the caldera formed in 1883 and is the current location of eruptive activity.
SPECIES AREA RELATIONSHIP Island with large areas have more species than islands with small area Species-area relationship is described by the empirical formula S=CA Z where S = number of species on an island A = Area of island Z&C= constants depending on type of islands and the types of species involved respectively [Value of Z ranges from 0.15 to 0.35 (typically around 0.25) Value of C is high in groups that are high in species number (e.g. insects) and low in groups that are low in species number e.g. birds]
EXTINCTION OF SPECIES IN ISLAND Extinction rate in Islands very high Of the 724 species of animals and plants known to have gone extinct, 351 species were island species Only 4 species of marine mammals and a limpet have gone extinct from the vast ocean
EXTINCTION SINCE 1600 A.D. Taxon Mainland Island Ocean Total Approximate number of species Percent of taxon extinct since 1600 Mammals 30 51 2 83 4000 2.1 Birds 21 92 0 113 9000 1.3 Reptiles 1 20 0 21 6300 0.3 Amphibians 2 0 0 2 4200 0.05 Fishes 22 1 0 23 19,100 0.1 Invertebrates 49 48 1 98 1,000,000+ 0.01 Flowering plants 245 139 0 384 250,000 0.2
Some Recent Extinctions New Zealand Since AD 1500, several species became extinct after Polynesian settlers arrived, including: Ten species of Moa, giant flightless ratite birds. The giant Haast's Eagle, Harpagornis The flightless predatory Adzebills.
Some Recent Extinctions Pacific, including Hawaii The Moa-nalos, giant grazing ducks from Hawaii. A giant megapode from New Caledonia. Mekosuchine crocodiles from New Caledonia, Fiji and Samoa. The Moa-nalos, giant grazing ducks from Hawaii. A giant megapode from New Caledonia. Mekosuchine crocodiles from New Caledonia, Fiji and Samoa.
Distinct Culture What are the problems of Island (socio-economic) Small economies Remoteness from International Market High cost of transport Limited diversification in production & Export Dependency on External Markets Vulnerability to exogenous economic shocks
What are the problems of Island Biodiversity Invasive alien species Tourism development Climate change and variability Natural disasters Overexploitation and unsustainable uses Pollution and waste disposal
OCEANIC ISLANDS OF INDIA Andaman and Nicobar group of Islands in Bay of Bengal Lakshadweep Group of Islands in Arabian Sea Jollybuoy Island
ABOUT A&N ISLANDS LOCATION Bay of Bengal North Andaman Middle Andaman NO OF ISLANDS 349 ANDAMAN GROUP 325 NICOBAR GROUP 24 Port Blair South Andaman GEOGRAPHICAL AREA 8249 Km² ANDAMAN GROUP 6268 Km² NICOBAR GROUP 1981 Km² Little Andaman TOTAL COASTLINE 1962 KM TEMPERATURE 18ºC -34ºC Car Nicobar AVERAGE ANNUAL RAINFALL 3000mm Great Nicobar Andaman & Nicobar Islands
World- about 250,000 PLANT DIVERSITY India over 45,000 A&N over 2,300 World India A&N No. of Plant Spp per 1000 Km² World 2 India 14 A&N 279 WORLD INDIA A&N
PLANT DIVERSITY contd 221(10%) endemic 40% of non-endemic have extra-indian distribution 40 spp. Extremely localised >50 spp. collected only once and never again Aglaonema simplex Ground Orchid
ANIMAL DIVERSITY No. of Species World 1,228,153 India 92916 A&N 5100 WORLD INDIA A&N
Faunal Diversity >5100 species recorded so far (survey incomplete) India A&N Endemism Mammals 390 62 (16%) 60% Birds 1232 246 (20%) 40% Reptiles 456 88 (19%) 30% (A & N Islands constitute 0.3% 0f India s geographic area) Marine diversity Fishes > 1200 sp. Corals > 179 sp. Molluscs > 1000 sp. Crustacea > 600 sp. Echinoderm > 350 sp.
Conservation & Management Issues Endemism Long Shore-line Invasive Alien Species Dear Elephants Influx of Population Tourism Development (Sustainable?) Encroachment Sand mining Many more
Distinct Culture What are the problems of Island (socio-economic) Small economies Remoteness from International Market High cost of transport Limited diversification in production & Export Dependency on External Markets Vulnerability to exogenous economic shocks
What are the problems of Island Biodiversity Invasive alien species Tourism development Climate change and variability Natural disasters Overexploitation and unsustainable uses Pollution and waste disposal
An Upland Moa, Megalapteryx didinus Elephant Bird-Aepyornis maximus
The Stephens Island Wren, victim of feral cat The species famously (but erroneously) claimed to have been made extinct by a single cat named "Tibbles".
Fast Facts about Islands Islands cover about 3% of the world s surface yet harbour a disproportional amount of biodiversity, and endemic species in particular One third of the world s conservation hotspots are islands Of 724 recorded animal extinctions in the last 400 years about half were island species At least 90% of bird species that have become extinct in that period were islanddwellers 12 of the 18 centres of marine endemism are around islands Seven of the 10 coral reef hotspots surround islands Many island species are endemic Over 90% of Hawaiian species are endemic 50% of all plants, mammals, birds, reptiles and amphibians in Mauritius are endemic The Seychelles has the highest number of endemic amphibians in the world Cuba has 18 endemic mammals, while nearby mainland Guatemala and Honduras only have three each Madagascar has over 8000 endemic species, the highest number of endemic species in sub- Saharan Africa and has vowed to protect 30% of its territory by 2020 Islands demonstrate the impacts of climate change and invasive species far before they are visible on larger land masses Islands are the most damaged by climate change without having contributed to it in any significant manner Small island developing States are among those with the most alarming rate of biodiversity loss.
What is an Island An island, strictly speaking, is a piece of land surrounded by water, beyond this stiupulation, there is no single accepted definition. The Millennium Ecosystem Assessment, for example, defines islands as lands isolated by surrounding water and with a high proportion of coast to hinterland ; stipulates that they must be populated, separated from the mainland by a distance of at least two kilometres, and measure between 0.15 square kilometres and the size of Greenland (2.2 million square kilometres).
Ring of Fire