HOW WATER LOSS AFFECTS BIODIVERSITY.
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In order for humans to live, they need access to fresh water. While nearly 70% of the
earth’s surface is water, most of it is salt water, which humans cannot drink. Only a small
percentage, about 3%, is fresh water. Of this, about 69% is currently frozen as ice caps and
glaciers, while another 30% is held underground in the soil or in rock. This means that only one
percent of the world’s fresh water—or .03% of the world’s total water—is surface water that
humans can access to drink. The small amount of potable (suitable for drinking) water makes
its conservation incredibly important so that water shortages already occurring in some
regions do not spread any further. If they do spread, this may lead to conflicts over the right to
use this water.
There are many ways in which humans can affect access to fresh water. For example,
humans can pollute bodies of water, thereby making them undrinkable. In some cases, they
may make physical changes to the land by building over wetlands or damming up rivers. While
wealthy countries can afford to make the investments necessary to make sure their residents
have access to fresh water, poorer countries often cannot. This means that poorer countries
are at greater risk of devastating droughts, which can lead both to dehydration and starvation,
as the country is unable to water its crops.
Droughts can also have a negative impact on the biodiversity of a region. Biodiversity
refers to an abundance of different types of plant and animal species within a particular
region. The prefix “bio” means living, while “diversity” refers to different types of things.
Around the world, more than 125,000 animal species live entirely in freshwater habitats,
How Water Loss Affects Biodiversity
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including 15,000 species of fish, 4,300 species of amphibians, and 5,000 species of mollusks,
such as clams and oysters. Millions of other species, including humans, depend on fresh water
to drink. When an area loses a large percentage of its fresh water, many animals die off. In
some cases, species go entirely extinct. This leads to a decrease in the region’s biodiversity.
While droughts are natural and, in many places, a frequent occurrence, there are many
things that humans do to increase the severity of these droughts. For one thing, the world’s
population has doubled in the last 50 years, so humans have been using much more fresh
water to drink and grow crops than they did in the past. Humanity’s increasing water
consumption represents a growing threat to biodiversity.
In Africa, where droughts are common, they have been more prolonged than in the
past. This is due in part to climate change, as well as a greater demand for water as the
continent’s population has increased. During a drought in Kenya that lasted from 2007 to
2009, over 60 elephants died—some of dehydration, others of starvation due to lack of
vegetation to eat, and others of diseases that became fatal due to the elephants’ weakened
states. Some other endangered animals, such as the white rhinoceros, died too, which brought
them closer to extinction.
When the biodiversity of a region declines, the human population suffers as well, in
different ways. When a region experiences a significant drought, many animals may die from
lack of water and food. If the region is one like Kenya, which depends on its wildlife to draw
tourists, the effects of the drought can be devastating. If tourism declines due to high wildlife
casualties, then the locals who depend on income from tourism will lose their livelihood.
People may then turn to farming to earn money, but crops require water to grow. This can
place further strain on the water supply and worsen the original problem of the drought.
Sometimes, an imbalance in the system, such as a lack of water, can enter into a feedback loop
where the situation only gets worse and worse.
Losses in biodiversity can also lead to problems with the availability of food. As we’ve
discussed, a lack of water can prevent farmers from growing crops, which can lead to
starvation. However, when a region loses its biodiversity, it disrupts the food chain in many
ways. For example, if a species goes extinct, all the species used to feeding on it must find
another source of food. Say a particular species of freshwater frog dies because its habitat has
been depleted in a drought. This means the population of birds that feeds on this frog may
decline as well, as it lacks sufficient food. Conversely, the insects that the frogs fed on may
increase in number, as the frogs are no longer around to keep their population in check.
How Water Loss Affects Biodiversity
© 2014 ReadWorks®, Inc. All rights reserved.
One of the main advantages of biodiversity is that there are certain natural processes
that plants and animals perform that humans simply cannot. The billions of bees in the world
play a critical role in pollinating the world’s flowers. If they did not do this, the food supply
would dwindle and the human population would suffer greatly.
Biodiversity can play an important function in the cleaning of water. When water passes
through lakes, wetlands, and streams, it often encounters different species of fungi, algae, and
bacteria. Many of these microbes actually filter microscopic particles out of the water, making
it safe for humans to drink. Even some larger species do similar work. For example, the
caddisfly constructs nets underwater that filter out different kinds of particles, which it then
eats. Wetlands rich with these filtering organisms act as natural water filtration systems.
When the biodiversity of a region declines, many of the organisms critical to this filtering
process can disappear. So, pressures on the freshwater supply can cause biodiversity to
decrease, which can cut the drinkable water supply even further.
While humans do have some water filtration plants, these plants are expensive and take
a lot of energy to maintain. For centuries the water that flowed into New York City was
naturally filtered by a northern watershed. As the water flowed south, it was purified.
However, as the watershed was polluted and diverted, the water flowing to New York City was
no longer filtered. The city faced a choice of spending $6 billion to $8 billion to build a water
filtration plant, or just $1 billion to restore the natural watershed. The city wisely chose the atter option.
Argument:
Water loss affects biodiversity by causing the decline of freshwater habitats and the extinction of species. This decline in biodiversity also leads to negative consequences for humans, such as water shortages, food scarcity, and economic impacts.
Supporting Points:
1. Only a small percentage of the world's water is freshwater that humans can access for drinking.
2. Human activities such as pollution and physical changes to land can affect access to fresh water.
3. Droughts, prolonged by factors like climate change and increased water demand, can lead to the death of animals and loss of biodiversity.
4. Losses in biodiversity can disrupt food chains and lead to food scarcity.
5. Biodiversity plays a critical role in natural processes such as water filtration, which is essential for human consumption.
6. Human interventions, such as water filtration plants, are expensive and energy-consuming compared to natural filtration systems.