Biodiversity is the variety of different types of life found on Earth and the variations within species. It is a measure of the variety of organisms present in different ecosystems. This can refer to genetic variation, ecosystem variation, or species variation (number of species) within an area, biome, or planet. Terrestrial biodiversity tends to be greater near the equator, which seems to be the result of the warm climate and high primary productivity. Biodiversity is not distributed evenly on Earth. It is richest in the tropics.
The impact of man on biodiversity can either be positive or negative, nevertheless some of its impacts can be outline and examine below;
Globally, over 1,000 (87%) of a total of 1,226 threatened bird species are impacted by agriculture. More than 70 species are affected by agricultural pollution, 27 of them seriously. Europe’s farmland birds have declined by 48% in the past 26 years (European Bird Census Council, 2008). Pesticides and herbicides pose a threat to 37 threatened bird species globally (BirdLife, 2008), in addition to deleterious effects of agricultural chemicals on ground water (Bexfield, 2008).
Domesticated species diversity is also under threat. Worldwide, 6,500 breeds of domesticated mammals and birds are under immediate threat of extinction, reducing the genetic diversity for options in a changing environment (Diaz et al., 2007; MA, 2005).
With the loss of biodiversity in both natural and agricultural systems comes the loss of other ecosystem services. In addition to food, fibre and water provisioning, regulating services such as air, water and climate regulation, water purification, pollination and pest control, as well as providing resilience against natural hazards and disasters and environmental change, are among the numerous examples of ecosystem services being lost under increasing intensification and expansion of agriculture.
After habitat loss, overharvesting has had the greatest effect on biodiversity. In fact, overharvesting and habitat loss often occur simultaneously, as removal of an organism from its environment can have irreversible impacts on the environment itself.
Humans have historically exploited plant and animal species in order to maximize short-term profit, at the expense of sustainability of the species or population. This exploitation follows a predictable pattern: initially, a species harvested from the wild can turn a substantial profit, encouraging more people to get involved in its extraction. This increased competition encourages the development of more large-scale and efficient methods of extraction, which inevitably deplete the resource. Eventually, quota systems are applied, leading to more competition, decreased earnings and the need for government subsidies to support the extraction industry.

Most of Quebec’s population (98%) and human activity occurs in the St. Lawrence watershed. Throughout the 20th century, degradation of the St. Lawrence has followed technological progress and urbanization and this has taken its toll. Pollution involves the addition of materials that are usually not present or present in very different amounts and can be due to the following factors:
toxic discharges: This includes metals, organic chemicals, and suspended sediments usually found in industrial and municipal effluents that are discharged directly into waterbodies. Toxic discharges can inversely impact the biota (living organisms) in an ecosystem by killing them, weakening them, or affecting their ability to carry out essential biological functions (feeding, reproducing, etc.).
With the urbanization of the population, proportionally fewer numbers of people were involved in food production. This led to changes in agricultural practices such as the development of modernized agricultural techniques with the use the moldboard plow, motorized tractors, hybrid cultivars, inorganic fertilizers and pesticides. This created new pressures on the land, dramatically increasing the influence of agricultural practices on biodiversity.

Human impact on biodiversity are enormous and gradually hurting mother earth, But it’s not all bad news. Many animal and plant species have adapted to the new stresses, food sources, predators and threats in urban and suburban environments, where they thrive in close proximity to humans. Their success provides researchers with valuable—and sometimes unexpected—insights into evolutionary and selective processes. Because these adaptations have had to be rapid, cities are, in some respects, ideal laboratories for studying natural selection.
Lastly, The impact of mankind on biodiversity has clearly been detrimental to many animals and plants, but the story is more complex and subtle than has been appreciated. Urbanization provides ready-made laboratories for studying evolution and adaptive processes, and examining the influence of humans on flora and fauna creates the potential to mitigate any negative effects. According to Marzluff, we should be more positive about our relationship with the natural world: We should celebrate the creative aspects of our impact on animals in addition to concerning ourselves with the negative effects.”

• “What is biodiversity?”. United Nations Environment Programme, World Conservation Monitoring Centre.
• • Gaston, Kevin J. (11 May 2000). “Global patterns in biodiversity”. Nature 405 (6783): 220–227. doi:10.1038/35012228. PMID 10821282.
• • Field, Richard; Hawkins, Bradford A.; Cornell, Howard V.; Currie, David J.; Diniz-Filho, J. Alexandre F.; Guégan, Jean-François; Kaufman, Dawn M.; Kerr, Jeremy T.; Mittelbach, Gary G.; Oberdorff, Thierry; O’Brien, Eileen M.; Turner, John R. G. (1 January 2009). “Spatial species-richness gradients across scales: a meta-analysis”. Journal of Biogeography 36 (1): 132–147. doi:10.1111/j.1365-2699.2008.01963.x.
• • Tittensor, Derek P.; Mora, Camilo; Jetz, Walter; Lotze, Heike K.; Ricard, Daniel; Berghe, Edward Vanden; Worm, Boris; Jetz, Walter; Lotze, Heike K.; Ricard, Daniel; Berghe, Edward Vanden; Worm, Boris (28 July 2010). “Global patterns and predictors of marine biodiversity across taxa”. Nature 466 (7310): 1098–1101. Bibcode:2010Natur.466.1098T. doi:10.1038/nature09329. PMID 20668450.

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