Major Threats to Biodiversity by Human Activities (Simple, Easy Ecology Lecture Notes)

‘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

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

(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

(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

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

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