Answer:
The UN projects that the global population increases from a population of 7.7 billion in 2019 to 10.9 billion by the end of the century. By that time, the UN projects, fast global population growth will come to an end.
Beneath the global level, there are of course, big differences between different world regions and countries. While in some regions the world population will likely grow rapidly for the coming decades other regions will continue to see declining population numbers.
Global population growth is determined by the number of births and deaths. Improving health is increasing the size of the population as it is decreasing mortality. The countervailing trend are falling fertility rates – the trend of couples having fewer children is what brought rapid population growth to an end in many countries already, and what will bring an end to rapid population growth globally.
The global population growth rate has already slowed down considerably: It reached its peak at over 2% in the late 1960s and has been falling since.
The UN projections for the global population growth rates, which have been produced since the 1950s, have a good track record in projecting the size of the global population.
While the UN projections are most widely know there are other very carefully produced projections. The demographers of WC-IIASA model what will happen according to different scenarios and make clear that the population growth rate tomorrow depends on what we do today. Rapid progress in getting children and especially girls into schools will result in a much smaller global population.
The biggest disagreement between different projections is concerning the future of Africa. While the UN projects a 3.5-fold increase of the population of Africa, other researchers find a much smaller increase more likely.
Explanation:
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Answer:
Eutrophication effect
Explanation:
The term eutrophication refers to the enrichment of surface water with nutrients. This process is related to human pollution activities.
Eutrophication is the biological process that generates in water by an oversupply of nutrients or organic matter. This matter, mainly compounded with nitrogen or phosphorous, favors the multiplication of phytoplankton (microscopic plants growing on the water surface) and other aquatic plants. This overgrowth leads to an enhance in primary productivity.
Little by little begin sedimentation, caused by the death of some vegetable organisms that sink in the bottom. These sediments rich in organic matter suffer decomposition in the presence of oxygen.
When oxygen disappears, anaerobic bacteria act and produce fermentation.
On the surface, plants and phytoplankton keep growing, creating a mantle that impedes the light to reach deeper areas. The overgrowth of phytoplankton on the water surface and the fermentation processes in the bottom originate toxic compounds that damage the animals. Animals die, creating more sediments in the bottom where there are anaerobic conditions. Decomposing processes and fermentation increases, producing a bad smell.
The result of eutrophication is the <u>stratification</u> of the water mass:
- <u>First superficial layer</u>, the overgrowth of blue-green algae produce toxins and interrupt the pass of light to deeper areas. The surface then becomes warmer.
- <u>The second layer</u> might have oxygen available for the animals.
- <u>In the third layer</u>, there is no oxygen, so life is not possible for animals or plants.
- <u>In the fourth layer</u>, there are animals and plants remains in the process of sedimentation.
- <u>At the bottom</u>, there is organic matter and anaerobic bacteria that are in charge of decomposition and fermentation, also producing toxic gases and smell.
