‘It is that range of biodiversity that we must care for – the whole thing –
rather than just one or two stars’
David Attenborough
What are major threats to biodiversity?
Major threats to biodiversity are:
1. Habitat destruction/Deforestation
2. Introduced and invasive species
3. Genetic pollution
4. Over exploitation
5. Hybridization
6. Climate change
7. Diseases
8. Human over-population
(1). Habitat destruction/Deforestation:
Ø Habitat destruction and deforestation has played a key role in extinction
Ø Habitat loss occurs when natural habitats are modified for human needs
Ø Factors causing habitat destruction are: Over-population, Deforestation, Pollution and Global warming
Ø Habitat size and number of species are systematically related
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Ø Physically larger species and those living at lower latitudes or in forests or oceans are more sensitive to reduction in habitat area
Ø Major reasons for habitat destruction are: Large scale industrial and commercial activities, Mining, Cattle rearing, Commercial fishing, Plantation cropping & Agriculture, Dam construction and Encroaching
Ø Habitat loss can leads to habitat fragmentation
Ø Habitat fragmentation: large natural habitats were get fragmented by human construction activities
Ø Habitat fragmentation is very critical for large and territorial animals such as elephants
Ø The breeding behavior of these animals are strongly depends on the size of the habitat they lives
Eichornia overgrowth over the water body
(2). Introduced and invasive species:
Ø Large barriers such as mountains, or seas support diversity in the area surrounded by these barriers
Ø This is by enabling independent evolution by allopatric speciation
Ø Invasive species: species that breach the natural barriers that would normally keep them away
Ø Invasions therefore can reduce diversity
Ø Invasive species eliminate native species by:
@. Occupying their niches
@. By using resources of native species
@. By competing with native species
@. Causing diseases to native species
(3). Genetic pollution:
Ø Endemic species can be threatened through the process of genetic pollution
Ø Genetic pollution occurs by the uncontrolled hybridization
Ø Genetic pollution causes: homogenization the genome of individuals and replacement of local genomes
Ø Hybridization is the side-effects of introduction and invasion
Ø Genetic pollution is more detrimental to rare species that come into contact with more abundant ones
Ø Abundant species immediately colonize new areas by vanishing the rare species
(4). Over exploitation
Ø Over exploitation occurs when a resources are consumed at an unsustainable rate
Ø Over exploitation of biodiversity occurs in the form of (1). Overhunting, (2). Excessive logging, (3). Poor soil conservation in agriculture, and (4). Illegal wildlife trade
Ø Illegal wildlife trade is the “largest threat” to biodiversity in Asia
Ø 25% of world fisheries are now overfished to the point where their current biomass is less than the sustainable mass
(5). Hybridization: (fusion of unrelated plants)
Ø Green Revolution popularized hybridization for increased yield
Ø Hybrid breeds originated in developed countries further hybridized with local varieties in developing countries
Ø This is to create high yield strains resistant to local climate and diseases
Ø High yielding breeds causes genetic erosion and gene pollution in wild species
Ø Genetic erosion and genetic pollution may destroy unique genotypes
Ø This creates a hidden crisis which could result in a severe threat to our food security or health
(6). Climate change:
Ø Global warming is one of the major threat to global biodiversity
Ø Coral reefs (biodiversity hotspots) will be lost in 20 to 40 years if global warming continues at the current trend
Ø Carbon dioxide concentration in atmosphere affects morphology of plants
Ø Higher carbon dioxide concentration acidify oceans
Ø In 2004, an international collaborative study on four continents estimated that 10% of species would become extinct by 2050 due to global warming
Ø Climate change induces change in raining pattern
Ø Climate change also affects migratory animals and birds
Ø Biodiversity in polar and mountain region are more vulnerable to climate changes
(7). Diseases:
Ø Diseases can eliminate species from earth
Ø The cause of disease may be natural or anthropological
Ø Human activities sometimes speedup the severity of natural diseases
Ø Introduced species may carries pathogens along with them
Ø Viral epidemics in animals is major threat to biodiversity
Ø Animals are more prone to disease than plants
Ø Animals in captivity are also prone to diseases
Click on the image for details (Source wikipedia)
(8). Human over-population:
Ø World population (as of July, 2015) is 7.3 billion
Ø In 1950 the population was 2.5 billion
Ø Population will reach 9 billion during the 21st century
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Ø Increase in population leads to over exploitation of resources
Ø Forest area will be reduced in the future
Ø Population increase ultimately cause pollution increase
Ø Population explosion thus form the prime factor biodiversity depletion
Ø Population increase can cause the other 7 main threats of biodiversity mentioned above