8.4 Human activity can affect local habitats

8.4

Human activity can affect local habitats

In this topic, you will learn that:

• organisms constantly have an impact on the environment around them (their habitat) • people make both positive and negative changes to the environment • understanding the impacts is the first step to reducing and reversing them.

Figure 1 Only one specimen of the Hastings River mouse has ever been found. It is considered extinct due to changes brought about by European settlement.

Figure 2 In 1983, large amounts of topsoil were carried across Melbourne and into the Southern Ocean as a result of wind erosion.

Animals use resources such as food and water and, in turn, provide resources for other organisms. Humans are certainly no exception. Human impact on environments is considerable because of our population numbers and our ability to manipulate our surroundings to suit our needs. Many environmental changes so far have been detrimental.

Deforestation

Our landscape was once covered by patches of different types of landscapes, such as swamp, grassland, forest and heath. This variety of vegetation supported many species of animals that moved, reproduced and spread throughout their territories and beyond. Since European settlement, over 44 per cent of Australia’s original bushland has been cleared. Much of that land is used for housing, to grow food or to manufacture products.

The food webs that existed in these areas have been changed as new predators (such as dogs and cats) move in and the number of producers decreases.

Land degradation

Human activities have led to a degradation of the physical environment. Soil erosion is a major problem caused by the clearing of land for agriculture. In ecosystems with many trees, the soil is stabilised by a dense mat of plant roots. Its surface is covered by a layer of leaf litter, which protects the soil surface from erosion by wind and water. Water from rainfall is quickly absorbed through the top layers of soil. Once land is cleared of trees for agriculture, there is little to protect the soil from the action of wind and water. Grazing by animals with hard hooves, such as cattle, compacts the soil. This slows water absorption into the soil and increases the amount of water run-off. This, in turn, erodes the soil. Wind also contributes to the removal of the nutrient-rich topsoil.

Urban sprawl

More than half of the world’s population lives in cities. The population in the world’s urban areas has grown by more than one billion people since the 1970s. Much of this growth has contributed to a phenomenon or process known as urban sprawl.

Urban sprawl means the spread of urban areas into rural areas, such as farmland, forests and coastal lands that lie on the outer edges of cities. Urban sprawl increases the distance between the city centre and its outer edge.

Urban sprawl is common in rapidly developing cities or those with large populations. Some of Australia’s cities rate among the world’s worst in terms of their sprawling nature, particularly because everyone wants their own garden and local parks.

A changing climate

Human activities are contributing to more significant changes to weather and climate. These changes can have a huge impact on ecosystems. In alpine areas, changing rainfall and temperature patterns alter the amount of suitable wet alpine habitat. This has made it difficult for animals that need the cool environments to survive.

Figure 3 Urban sprawl around many of Australia’s capital cities is on the increase.

Figure 4 Alpine areas are reducing as the climate changes.

8.4 Check your learning

Remember and understand

1 Define the term ‘urban sprawl’. 2 Suggest four things you can do to reduce the damage you may do to the environment (your ecological footprint).

Apply and analyse

3 The ‘Australian dream’ is a term that has been used to describe the wish of many Australians to own a home on a block of land in the suburbs. Describe the problems that are caused by many Australians ‘living this dream’.

4 Each winter the cold weather causes the mountain pygmy possum to hibernate (deep sleep). This allows the possum to save energy when the food supplies are low during the winter. Explain how a warming climate could affect the mountain pygmy possum’s ability to hibernate and survive each winter. Evaluate and create

5 Create a two-column table with the headings ‘Problems’ and ‘Solutions’. In the

‘Problems’ column, list the things that people do that affect wildlife, such as building homes and roads, and cutting down trees.

In the ‘Solutions’ column, propose some solutions to each problem.

Figure 5 A mountain pygmy possum