Habitat Destruction CHAPTER 23

23.1 The Loss of Biodiversity  Extinction – the disappearance of a species from all or part of the species’ geographical range  Biodiversity – the variety of species in an ecosystem

The Loss of Biodiversity  Every species has a specific habitat that supplies it’s needs  Destruction of this habitat decreases the geographical range of a species

Extinction  Extinction are a natural part of ecosystem function  More than 99% of species that have lived on earth are extinct today  Species that lack adaptations for survival in a changing ecosystem become extinct

Extinction  Rate of extinction and species appearance are not steady  See Figure 23.1  Today may be another period of mass extinction because of dominant species: humans

Loss of Habitat  Extinctions and loss of biodiversity often occur as a result of human activity  Habitat destruction – disturbing the part of an ecosystem that an organism needs to survive  Forms:  Land development (draining swamps/wetlands to create, housing complexes, marinas, farmland, etc.)  Altering the course of rivers: dams  Mining and quarrying

Loss of Habitat  Native species are threatened by non-native species  Alien species (invasive species) – non-native species introduced to an area by humans  Examples: water hyacinth – introduced in Louisiana from S. America has invaded 800,000 hectares of rivers and lakes across US to California; outcompeted native plants

Loss of Habitat  Human activity is destroying or altering habitats in all biomes  Urban sprawl – humans looking for a place to live

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23.2 Humans and Habitats  150 years ago rainforests covered an area of earth’s surface larger than the US  Percentage of destruction is equal to an area the size of the state of Oregon (deforestation)

Causes of Deforestation  All rain forests are in developing countries  These countries are usually poor and have rapidly growing populations  Figure 23.3

Population Growth  Populations in developing countries need food and living space  Soil in rainforests is nutrient-poor so removal of plants leads to mass erosion  Most of this land becomes barren and unproductive in a few years

Demand for Resources  Developing nations have resources that developed nations want  Rainforests in the Philippines, Thailand, Borneo, and Indonesia are a large source of timber for developed countries such as Japan and other nations

Demand for Resources  In Central and S. America grass-fed beef is in high demand so rainforests are cleared for grazing lands

Demand for Resources  Rain forest regeneration times are unknown  It is estimated to be from hundreds to thousands of years  If it is all destroyed, no organisms will be left to fill in niches  If all rain forests are destroyed 70% of biodiversity is lost from earth

Aquatic Habitat Destruction  All biomes are losing biodiversity  Wetlands and coral reefs are very productive ecosystems  Both are affected by pollution and development

The Everglades  The everglades are a large group of marshes in southern Florida  Habitat for many organisms: grasses, fish, invertebrates, and migrating birds  Everglades are prime real-estate property which has been developed for housing and recreation

The Everglades  More than half of all wetlands in the US have been destroyed  An estimated 175,000 hectares are destroyed annually  US Congress and the State of Florida are working to restore at least part of the everglades to their natural state

The Aral Sea  The Aral Sea is a large, salt-water lake in a southern desert of the former Soviet Union  See Figure 23.5  Used to be fourth largest lake in the world  Rivers were diverted for irrigation  Used to be 1000km 3 ; now only about a third its size  Loss of 68,000km 2 is very serious  Loss of aquatic ecosystems that fed fishing industry

23.3 The Importance of Biodiversity  Why is habitat destruction undesirable if it is a natural part of all ecosystems?  Two part answer:  1. humans benefit directly from high biodiversity  2. the loss of biodiversity threatens the health of the global ecosystem, and indirectly threatens human health

Crop Genetics  Direct benefits of biodiversity include new genetic material for farm plants  About 30 species of plants are grown as crops  Selective crossing produces plants with higher yields

Crop Genetics  Genetic material from wild plants strains is used to improve food crops  1978 – a variety of wild corn was found in Mexico  Crossbreeding with this wild type meant farmers didn’t have to plow and sow from season to season

Crop Genetics  Genetic material makes the global food supply more flexible  Pathogens and insects evolve leaving crops vulnerable  New varieties are need to survive evolving pathogens  Habitat destruction threatens the survival of wild type crops

Medicines  Natural chemicals are used in medicines  About 40% of all medicines used in the US come from plants  Quinine – used to fight malaria – comes from Cinchona plant  Digitalis – used to treat heart disease – comes from foxglove  Some cancer treatments are being researched using leaves from periwinkle plants and bark of the pacific yew

Medicines  Unknown other medicines are undiscovered in the rainforests  Habitat destruction may mean that many medicines may never be discovered

Wilderness Areas  Other effects of declining biodiversity include loss of recreational areas  Wilderness – an area where the ecosystem is relatively undisturbed by the activities of humans

Ecosystem Destruction  Most dangerous characteristic of current mass extinction is the pattern  Past extinctions follow a pattern  Extinction of dinosaurs left many species to fill in gaps  Extinction today is the removal of many species

23.4 Controlling Habitat Destruction  Many rainforests lie in developing countries  Developed countries drive the cause of their destruction in many cases  Developed countries can help slow its destruction by decreasing demand

International Efforts  Progress has been made  Gene bank – a secure place where seeds, plants, and genetic materials are stored  Gene banks are working to preserve as much of earth’s biodiversity as possible (just in case)  Ending habitat destruction is the best idea though

The Endangered Species Act  1973 – US Congress passed The Endangered Species Act  Law requires the government to create a list of endangered species in the US that are endangered of becoming extinct  Government must help protect these species

Provisions of the Endangered Species Act  US Fish and Wildlife Service keep a list of endangered or threatened species  Threatened or endangered species may not be killed or caught  Threatened or endangered plants may not be disturbed  Threatened or endangered species and products may not be bought or sold  Federal government may not construct any project that jeopardizes endangered species  The US Fish and Wildlife Service must prepare a species recovery plan for each threatened or endangered species