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IELTS READING LEVEL 7.5 – How Water Loss Affects Biodiversity

How Water Loss Affects Biodiversity

by ReadWorks

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, 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.

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. Therefore, 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 latter option.




biodiversity       bi ·o ·di ·ver ·si ·ty

Advanced Definition


  1. the diversity of life forms on earth or part of the earth, including diversity of species, genes, and ecosystems, esp. when regarded as providing the optimal conditions for evolution.

Spanish cognate

biodiversidad: The Spanish word biodiversidad means biodiversity.

These are some examples of how the word or forms of the word are used:

  1. Environmentalists from the group Conservation International say this area of the northern Amazon has more biodiversity than all tropical forests on the planet. Biodiversity is the variety of plants and animals in an environment. The Amazon is home to more species, or types, of plants and animals than any other place in the world.
  2. Where are the most biologically diverse places on the planet? If I asked you this question, you might guess the Amazon rainforest in Brazil or the jungles of India. But, in fact, one of the richest sources of biodiversity is actually underwater. Off the northeastern coast of Australia live thousands of species of fish, birds and reptiles.
  3. Biodiversity is a general term that describes diversity among plant and animal species in a given environment or ecosystem.
  1. Wildlife groups are against the plan. They say it is imperative, or absolutely necessary, to protect Bird’s Head Seascape. “It’s extremely important because this area is the center of coral reef biodiversity,”
  1. Despite the biodiversity in the rainforests of the Southern Hemisphere, many species are quickly becoming extinct, as people cut down trees and destroy natural habitats. Other threats to species of the rainforest include illegally trading monkeys for their fur as pets, or for scientific research, and killing jaguars for their highly valued skins. Pollution from mining has killed many types of fish as well.
  2. First, these changes in the Amazon will decrease the biodiversity of the rainforest. This means there will be fewer rare plant and animal species living there, and some species may go extinct as their habitat changes.
  3. This particular study highlights the importance of bees to the continuation of, not just our food supply, but also all biodiversity, as the effects of this study do not end with the larkspur plant alone, but point to a much larger issue. The larkspur is just one example of this issue.
  4. Food chains can get much longer and more complicated, though, resembling webs more than linear chains. The word commonly used to describe the relative number of different species in an ecosystem is “biodiversity,” and the more biodiversity within the ecosystem, the more complex the food web.


conservation       con ·ser ·va ·tion



  1. the protection of natural resources such as soil, water, or forests from harm.

Water conservation is important for people’s health.

Advanced Definition


  1. the act of preserving and protecting from loss, destruction, or waste.
  2. the preservation of a resource, esp. a natural resource such as soil, water, or forests, from loss, pollution, or waste.

Spanish cognate

conservación : The Spanish word conservación means conservation.

These are some examples of how the word or forms of the word are used:

  1. Conservationists regularly take up arms against plant and animal invaders by trapping, hunting, poisoning, or bulldozing them.
  1. “Getting rid of zoos would be a tragedy for all animals,” says Steve Feldman, senior vice president of the Association of Zoos and Aquariums. He says zoos play a major role in educating people about animals and promoting wildlife conservation.
  1. Because of overhunting and habitat loss, tree kangaroos are endangered. In 2009, after Dabek and her team spent 10 years working with hunters and landowners on the Huon Peninsula, the community set aside more than 70,000 hectares (173,000 acres) of forest for conservation.

It’s the first preserve of its kind in the country. People have agreed not to log, mine, or hunt tree kangaroos in the protected area, even though the animals are traditionally part of the local diet.

  1. That all changed 10 years ago when Dontego heard an American conservationist talk about why poaching was not only illegal but also wrong. Although Dontego killed the elephants to feed his family, he felt guilty about being a poacher. Now Dontego works for an environmental group that wants to protect the elephants and end the ivory trade.
  2. Countless seabirds have since benefited from Kress’s ingenuity. Seabirdconservationists around the globe have adopted his techniques to reestablish almost 50 species in 14 countries, including petrels in New Zealand and albatross in Japan. “That was always my hope,” says Kress, “to extend this beyond the puffin.”
  3. The Journey Through Hallowed Ground Coalition, an association of more than 100 conservation groups, wants to strike a balance between development and preservation.
  4. “For us, conservation of vultures is closely linked to religion,” Mistree said. “We leave our dead bodies exposed to the sun so as to be devoured by the birds, and the vulture is the most important of these birds of prey.” With fewer vultures consuming the dead, the Parsis’ age-old tradition is dying, he added.
  5. Habitat destruction threatens Borneo’s wildcats. Scientists have called for increased conservation, or protection, of the rain forest habitat on Borneo-the world’s third largest island.
  6. As erosion has become a bigger problem in past decades, scientists have been working to better understand the phenomenon. In 1965, American scientists came up with the Universal Soil Loss Equation, a way to estimate soil erosion by raindrop impact and surface runoff. The mathematical equation has since been applied all over the world, helping scientists predict which conservation measures will have the greatest impact on reducing soil loss.


feedback       feed ·back

Advanced Definition


  1. the returning of opinions, corrections, or other evaluative information after exposure to a product, process, or event.

There was a great deal of feedback from customers about the new product, and most of the response was positive.

  1. the evaluation or evaluations thus returned.

The students’ feedback contained several complaints concerning the textbook.

  1. the return of information about the functioning of a machine process, so that the process may be automatically regulated.
  2. the information thus returned.
  3. in electronics, the return of part of the output of a device or system to the input, so as to reinforce or modify the input.
  4. in an audio system, a whistling or screeching noise made when the output signal is picked up at the input.

These are some examples of how the word or forms of the word are used:

  1. Why are scientists able to understand some phenomena, like climate change, in a general way, but aren’t able to predict the changes they will have on the Earth? Part of the reason is because many large Earth systems involve “feedback loops” – processes that help amplify (positive feedback loops) or diminish (negative feedback loops) certain changes.
  2. At the same time Gordon says he never knows quite what he’s doing whenhe pulls the tuning hammer. Much of the work is done by feel. “It’s automatic andbased on the feedback I get from the piano, the note, the ear,” he says. He attaches the hammer to the top of the tuning pin, sounds the note, listens and makes an adjustment with the hammer. He makes short, swift adjustments and always tests the note repeatedly. He places foam mutes inside the piano to isolate individual strings.


Name: ___________________________________ Date: _______________
Comprehension Questions
1. What is biodiversity?
A. a lack of different types of plant and animal species within a particular region
B. an abundance of different types of plant and animal species within a particular region
C. the different types of plants and animals that live in freshwater habitats
D. a method of conserving the planet’s small amount of potable water
2. The cause of humanity’s increased water consumption is an increased population. What is the effect?
A. less potable water, a growing threat to biodiversity
B. more potable water, a growing threat to biodiversity
C. less potable water, a decreased threat to biodiversity
D. more potable water, a decreased threat to biodiversity
3. Poorer countries are at greater risk during droughts than richer countries. What evidence from the passage supports this conclusion?
A. With no water for crops, droughts can lead to starvation and dehydration.
B. Droughts in Africa have been more prolonged than in the past due to climate change.
C. During droughts, many animals die, and sometimes whole species go extinct.
D. Poor countries often cannot afford investments that ensure access to fresh water.
4. Read the following sentences: “When the biodiversity of a region declines, many of the organisms critical to this filtering process can disappear. Therefore, pressures on the freshwater supply can cause biodiversity to decrease, which can cut the drinkable water supply even further.”
Based on this information, what can be concluded?
A. Water supply and biodiversity are unrelated.
B. Biodiversity affects the fresh water supply, but not vice versa.
C. Water supply and biodiversity are interconnected.
D. The fresh water supply affects biodiversity, but not vice versa.
5. What is this passage mostly about?
A. the effects of water loss on biodiversity
B. the drought in Kenya from 2007 to 2009
C. the distribution of the world’s fresh water
D. the effects of population growth on the water supply
6. Read the following sentences: “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.”
What does the word “conversely” mean?
A. in the same vein
B. for this reason
C. as an example
D. on the other hand
7. Choose the answer that best completes the sentence below.
Humans can affect access to fresh water in many ways, ________ polluting bodies of
water and building dams.
A. finally
B. such as
C. initially
D. although
8. What makes the conservation of fresh drinking water so important?
9. Describe a problem caused by losses in biodiversity.
10. How might humans help prevent losses in biodiversity? Use information from the passage to support your answer.
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