Gobar Times
Open Forum

Species Shift



Sameer: Hi Tanushree! What did you do in your winter vacation? I went to Mumbai to escape the Delhi winter… The weather’s much better there.
Tanushree: I was in Delhi, preparing for the exams. But yes, I managed to convince my parents to take me to Bharatpur Bird Sanctuary for few days. The trip was great!
Sameer: But, why did you go to a bird sanctuary in this cold weather?
Tanushree: Silly, this is the time when migratory birds come to the Park.

Sameer: They come to India to spend the inters… why?
Tanushree: Well, there are quite a few reasons as to why birds go from one place to the other… through migration and translocation. And it is not only birds that move, many animals and even human beings do.
Sameer: Huh? Migration and translocation… what are these?
Tanushree: It seems you don’t pay heed to what you are taught. Now, let me explain.

Migration and translocation are two different types of movement of species.

Migration is the seasonal or periodic movement of animals due to changes in climate or food availability, or to ensure reproduction. It is generally a round-trip – moving from one area to another and then back again.

However, some trips may take a lifetime to complete! For example, various species of Pacific salmon born in freshwater streams, travel to ocean waters, and then return to the stream where they were born to breed before dying.

Translocation, on the other hand, is the movement of species from one area to another by people. There are three types of translocations:
Introduction – the deliberate or accidental movement of a species in areas where it does not occur naturally and has not occurred during historic time.
Re-introduction – the translocation of a species in areas where it was indigenous in historic times but is no longer present.
Re-stocking – the addition of an organism into an area where it is already present.

Sameer: Ok. So, migration is natural, while human beings aid in translocation of animals. But, why would we shift animals from one place to the other?
Tanushree: Sometimes, it happens accidentally. Say, when people and goods travel internationally. For example, three species of rat – the Black, Norway and Polynesian – have spread to most of the world as hitchhikers on ships. But often, people shift species intentionally for various reasons like…

Translocation has various advantages like introduction of new species into an area may have benefits like economic development, improvement of hunting and fishing, ornamentation, or maintenance of cultures by incoming settlers in the area. But, the most important reason is conservation of endangered species.

When a certain species becomes extinct due to human activities, over-collecting, over-harvesting, or habitat deterioration, the species is re-introduced for restoring the habitat. For instance, zoological parks play an important role in the re-introduction of captive-bred animals into the wild.

Restocking, on the other hand, is done where populations have dropped below critical levels, and cannot be naturally recovered. Say, in populations with slow reproductive rates or inbreeding.

Populations of some endangered species become so small that they lose genetic variation. To avoid extinction, individuals from related sub-species or populations are introduced for genetic restoration (recovery to a normal level of genetic variation).

However, translocation, especially introduction of new species into an area, is a highly debated topic. Generally,
the damage done by introductions far outweighs their benefits to biodiversity. Even the reviews of translocation projects of birds and mammals suggest that the success rate is low. The chances of getting exotic pathogens in the species, which may cause various diseases, are quite high. But, the biggest fear is that of invasion by the alien species.

Once alien species enter a new location, they establish a breeding population, and spread throughout the new area. They compete for limited resources or prey on the native species. They may even hybridise with them. This may lead to a decline and even extinction of the native species. Their invasion can

-- Reduce biodiversity
-- Degrade habitats
-- Alter native genetic diversity
-- Transmit exotic diseases to native species and even human beings. For instance, the West Nile virus spread across North America because of the entry of an infected bird or mosquito vector. It resulted in the death of humans, birds, mammals, and reptiles.
-- Cause production loss in agriculture and forestry from seed contamination to cultivation of exotic species.

Satyanashi (Argemone mexicana) – In the 17th century, ‘satyanashi’ or the Mexican prickly poppy was brought to India from Mexico and Central America. In 1998, it caused a dropsy epidemic in Delhi killing 60 people and hospitalising thousands.
Lantana (Lantana camara) – The British planted it in the National Botanical Gardens, Calcutta, in 1807. Introduced for ornamental purposes, it took over India’s landscape in the blink of an eye, killing many native plant species, and becoming one of the 100 most invasive species.
Carrot Grass (Parthenium hysterophorus) – Commonly known as Chatak Chandni or Congress Weed, it entered India by accident. It came from America along with imported wheat. It is dangerous to crops, animals and human beings, and responsible for afflictions ranging from asthma, bronchitis, and hay fever to dermatitis – in both humans and livestock.
Green crab – In the mid 1990s, the introduction of the European Green Crab led to disaster. It preyed preferentially on the native clams. This resulted in a decline of the native clams and an increase of the introduced Green Crab populations.
Asian Long-horned Beetle – It was first introduced into the United States in 1996 and has infected and damaged millions of acres of hardwood trees. Millions of dollars have already been spent in attempts to eradicate this pest and protect millions of trees in the affected regions.
Sika Deer – They were introduced in many countries like Australia, Austria, Denmark, Germany, Britain, France, Ireland, New Zealand, Poland, Morocco and the United States (Maryland and Texas), mainly as ornamental animals in parklands. But, they often hybridise with the native Red Deer, which is a serious conservation concern.
Gray Squirrel – It was introduced in several regions of the western United States, and countries like Britain, Ireland and Italy. It has largely displaced the native Red Squirrel.

Sameer: This means we, human beings, are as usual responsible for causing havoc in the natural environment!
Tanushree: Unfortunately, yes.
Sameer: Thank God, at least these species migrate on their own, and it is not our fault. Phew!

Tanushree: Actually, we may affect migration as well.
Sameer: Oh no! How?

Habitat destruction by land-use practices is the biggest threat to migratory animals. For instance, shallow wetlands that are stopovers and wintering sites for migratory birds are often destroyed by draining and reclamation for human use. Human-made structures act as hurdles for the migrants.

  • Skyscrapers and radio towers cause the deaths of thousands of migrating birds.
  • Structures such as power lines, wind farms and offshore oil-rigs affect migrants, especially birds.

Dam construction in some areas has made it impossible for fish to swim upstream to spawning areas. Hunting along the migratory route also takes a heavy toll on these animals. For example, the populations of Siberian Cranes that wintered in India declined due to hunting along the route, particularly in Afghanistan and Central Asia. Another example is that of the caribou of Arctic regions, which are hunted by Inuit who intercept herds along seasonal migration routes. To add to the troubles, sport hunters also follow the migration routes. In the fall, for instance, goose and duck hunters hunt on specific feeding grounds on their migratory routes. Hunters anticipate the movements of elk, which usually migrate to lower elevations of mountain ranges in the winter, and hunt them down. But, there is far graver danger – climate change.

Migration and climate change
The relation of human-induced climate change and migration is quite apparent. Migratory species are in many ways more vulnerable to climate change than other species, as they use several habitats and sites, and a various resources during their trips.

  • Seasons - Migration depends on seasonal changes in the climate/weather. For instance, in winter, animals that depend on fish or aquatic plants  from waters in the north find their feeding grounds sealed by ice. So, they travel south in order to survive. But what will happen if the pattern of  seasons is interrupted? Their migratory pattern and habit will change. The same thing holds true for insects, animals, and birds.
  • Route change - The length, timing and location of migration routes are already changing. In extreme cases, species have abandoned migration altogether. Some species now migrate to areas where they have not been recorded other than as occasional vagrants. Changing wind patterns, for instance, are making it more difficult for passerine birds to make their migration in the Caribbean where spring storms are becoming more numerous and of greater intensity.
  • Food - Climate change also affects the availability of food or prey. For example, small ocean animals called krill, which form the base of the food chain, may perish, as they are not that tolerant to warmer water. This will have repercussions for species higher up the food chain, including penguins, albatrosses, seals and cetaceans. “Species that migrate across countries and continents are facing ever greater hurdles from loss of habitat and feeding grounds to unsustainable use and the unfolding and often complex threats emerging from climate change”, says Achim Steiner, UN Under- Secretary General and Executive Director of the United Nations Environment Programme (UNEP), which administers the Convention on the  Conservation of Migratory Species of Wild Animals (CMS).

Sameer: Oh! It seems like we affect each and every aspect of the environment, Tanushree. Is there anything that we can do to save these animals and birds?
Tanushree: Surely. Many countries are already trying their level-best to protect these animals. Several international treaties have been signed to protect migratory species, including the Migratory Bird Treaty Act (1918) of the US and the African-Eurasian Migratory Waterbird Agreement. Programmes for the translocation of an animal are also subject to legislation, which are applied at international, national, regional, or local levels. It can relate inter-alia to conservation, animal health, welfare and research, administration, and to human safety.

However, the bottom line is that we must protect the environment. Our every action affects all the species that exist on this planet. If we want, we can destroy the natural balance of nature, and if we want, we can also make it better. It all depends on us…

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Species Shift