Five Major Threats to Biodiversity in Ecosystems

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1 Five Major Threats to Biodiversity in Ecosystems Ecosystems around the world are home to an astounding number of organisms. Scientists predict that there are at least 8.7 million different species of plants, animals, fungi, and other organisms in the world. Most of them have not even been identified yet! The word biodiversity describes the many different types of life that exist on our planet. Biodiversity means a healthier earth, because each organism has a role that helps keep its ecosystem in balance. Unfortunately, biodiversity is being threatened as ecosystems around the world get changed, damaged, or destroyed. Normally, changes to ecosystems happen slowly enough that organisms have a chance to adapt (or change) to fit the new environment. Today, however, humans are changing the world much faster than organisms can adjust. Humans are the major cause of extinctions and loss of biodiversity on Earth. In just the last century, the extinction rate has increased to alarming levels. Continue reading to learn about the five biggest threats to ecosystem health and balance. Think of them as the Frightening Five, because any of these can create changes that will have long-term affects on the world around us. The more you understand about the ways that we affect the environment, the better you will be able to learn how to reduce the human impact on Earth.

2 Threat #1: Habitat Destruction Currently, the biggest threat to biodiversity is habitat destruction. Habitat destruction is, quite simply, taking away space that organisms need to live. When an ecosystem has been changed by human activities, it may no longer be able to provide the food, water, shelter, and places to raise young. Every day there are fewer places left that wildlife can call home. Habitat destruction happens on land, in lakes and rivers, and in the ocean. There are many ways that we destroy habitats: Deforestation Humans destroy forests to clear land for agriculture, or to cut down trees for timber. Although forests cover 31% of land, they are shrinking at an alarming rate. Rainforests are especially vulnerable as much as 17% of all rainforest has been destroyed over the last 50 years. Most threatened and endangered species live in forests, and that number will continue to grow as more forests are destroyed. Construction As the human population grows, so does our need for land to build homes, roads, stores, schools, etc. As humans move into new areas, it forces the organisms in that habitat to leave and search for new places to live. This gets more and more difficult as the area of available land continues to shrink. Building Dams and Draining Waterways Building dams changes the natural flow of rivers and lakes. This can affect the reproductive habits of aquatic organisms, resulting in loss of life. Meanwhile, draining waterways kills all of the organisms that need this water to survive. Habitat destruction can be harmful at the species level, or at the larger community and ecosystem level. There are few parts of the world that have not been affected by human activities, and technology is speeding this process up. It is estimated that, by the year 2032, more than 70% of Earth s surface will have been disturbed or destroyed.

3 Threat #2: Human Use of Plant and Animal Species Plants and animals are some of the most important resources available to humans. We use them for food, shelter, clothing, medicine, pets, sport, and many other uses. But as the human population on Earth grows larger, we are using more than the natural world can supply. We are hunting, trapping, and collecting organisms faster than they can be replaced. The problem is that once the population of a species gets below a certain level, it is very difficult for the population to recover, and the species faces extinction. Here are some common overuses of plants and animals: Overfishing seafood is a valuable food source, especially for coastal areas. As technology improves, and as the worldwide demand for seafood grows, humans are removing more aquatic life than is replaceable. Many common fish and shellfish are in serious decline due to overfishing. Illegal Hunting While domesticated cattle are specifically bred for use as food, other species are in danger of extinction due to overhunting. Whether they are hunted for food, fur, skins, horns, or just for sport, these animals are killed at a faster rate than they can reproduce. Elephants, tigers, rhinoceros, crocodiles, and sharks are just a few examples of overhunted species. Overharvesting of Plants People harvest plants for food, medicine, building supplies, and as raw materials for other products, such as clothing or paper. But we are taking too many plants from the wild, much faster than they can reproduce. For example, the ginseng plant, which is used for medicine, is now very difficult to find in the wild. And mahogany, a tree which is prized for the beautiful color of its wood, is now endangered in some areas.

4 Threat #3: Invasive Species An invasive species is any type of living organism that is not native to an ecosystem and which causes harm. Organisms can be moved from one ecosystem to another, either accidentally or on purpose, in many ways. For example, aquatic organisms can attach to boats moving through the ocean; insects can burrow into wood that is being transported; and many plants or animals are purposefully transported by humans for use as decorations or as pets. Once a species has moved into a new environment, it is considered invasive if it is aggressive to native species; reproduces quickly; and causes harm to the environment. Invasive species populations usually grow very quickly, because there are no natural predators to control the population numbers. Invasive species can harm ecosystems by: Preying on Native Species: this upsets the balance of the ecosystem by altering the food web. When additional predators are added, the prey population becomes threatened. Out-competing Native Species for Food or Other Resources: there are only so many resources available in an ecosystem. This is called the carrying capacity. When the population of the invasive species increases, it means more organisms will be competing for limited resources. Spreading Disease: Some invasive species carry disease. The native species have no natural protection against the foreign disease. For example, West Nile Virus (which is very dangerous to humans) is quickly spreading through the United States after the Asian Tiger Mosquito was transported to New York in Since then, nearly every state in the U.S. has reported cases of West Nile Virus. Preventing Native Species from Reproducing, or Killing Their Young: When invasive species prevent native species from reproducing or when they kill their young for food it causes the population to decrease. This affects other animals that need the native species for food.

5 Threat #4: Pollution There are many types of pollution - humans pollute our atmosphere, water supplies, and land. When an ecosystem gets polluted, the natural balance in the system is disturbed and affects the organisms in different ways. Pollution can be accidental or purposeful, but however it happens, it can have lasting effects on ecosystems. Here are some ways that pollution affects ecosystems: Land Pollution from dumping unwanted trash, to using pesticides and other chemicals, pollution of our natural lands affects ecosystems. Dangerous chemicals that get eaten by animals can pass from one animal to another, causing disease and death throughout the food chain. Animals also mistakenly eat litter, which can cause health problems or even death. Water Pollution this includes oil spills or illegal dumping of chemicals into lakes, rivers, or oceans. This poisons both plants and animals, and can result in dead zones in lakes or ponds. Noise Pollution Many people do not realize how much noise affects wildlife. The noise from construction equipment or even the noise from people living nearby can frighten wildlife and cause them to leave the area. This affects other animals in the area that lose their food supply. Threat #5: Climate Change Many organisms can only live in certain temperature ranges. If it gets too hot or too cold, that organism dies. As global warming causes climate changes around the globe, ecosystem temperatures are changing faster than organisms can adapt. Changes in Water Temperature: As water temperatures increase, the higher temperatures can kill fish or other aquatic organisms. Also, warmer temperatures can cause the oxygen levels in water to decrease, so aquatic organisms might suffocate and die. Changes in Weather: Global warming threatens to change weather patterns around the world. This can result in droughts or too much rain, which impacts the living things that need certain amounts of water to survive. It can also cause colder winters or warmer summers, which can affect organisms that cannot adapt to these extreme temperatures. Changes to Food Chains: Climate change can also affect food chains. For example, in the Antarctic, warmer temperatures are causing a decline in ice algae. The ice algae are eaten by zooplankton, which are eaten by cod fish, which are then eaten by seals, which are then eaten by polar bears. So the decrease in ice algae will have negative effects on all of the organisms along the food chain.