This Chapter will cover• Definition of Ecosystem• Types of Ecosystem• Terrestrial Ecosystem• Aquatic Ecosystem• Importance of each Ecosystem
Ecosystem:An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving (abiotic), physical components of the environment with which the organisms interact, such as air, soil, water and sunlight.
Types of Ecosystem:• Natural – Terrestrial ecosystem – Aquatic ecosystem – Lentic, the ecosystem of a lake, pond or swamp. – Lotic, the ecosystem of a river, stream or spring.• Artificial - ecosystems created by humans.
• Terrestrial ecosystemsTerrestrial ecosystems are found everywhere apart from water bodies. They are broadly classified into:There are seven major types.Location usually dependent on the latitude of the area, and amount of precipitation
The Forest Ecosystem• These are the ecosystems where abundance of flora (plants) is seen and they have a large number of organisms living in relatively small areas. Therefore, the density of life in forest ecosystems is very high. Any small change in the ecosystem can affect the whole balance and collapse the ecosystem.
Tropical evergreen forest:Tropical forests which receive an average rainfall of 80 to 400 inches in a year. These forests are marked by dense vegetation comprising of tall trees with different levels. Each level gives shelter to different kinds of animals.
• The Grassland Ecosystem• Grasslands are found in both temperate and tropical regions of the world but the ecosystems are slightly varying. This area mainly comprises of grasses with very little amount of shrubs and trees. Main vegetation is grasses, legumes and plants belonging to composite family. Many grazing animals, herbivores and insectivores are found in grasslands. Two main types of grasslands ecosystems are:
Savanna: These tropical grasslands are seasonally dry with few individual trees. They support large number of grazers and predators.
Savannas• Precipitation 90-150cm/year• Open, widely spaced trees, seasonal rainfall• Parts of Africa, South America & Australia
Prairies: This is temperate grassland. It is completely devoid of trees and large shrubs. Prairies can be categorized as tall grass, mixed grass and short grass prairie.
• The Mountain Ecosystem Mountain lands provide a scattered but diverse array of habitats in which a large range of plants and animals are found. At higher altitudes harsh environmental conditions generally prevail, and only treeless alpine vegetation is found. The animals living here have thick fur coats fro prevention from cold and hibernate in winter months. Lower slopes commonly are covered by coniferous forests.
The Desert EcosystemDesert ecosystems are found in regions receiving an annual rainfall of less than 25cm. They occupy around 17 percent of all land on the planet. Due to very high temperature, intense sunlight and low water availability, flora and fauna are very poorly developed and scarce. Vegetation is mainly bushes, shrubs, few grasses and rarely trees. Leaves and stems of these plants are modified to conserve water. The best known desert plants are the succulents like spiny leaved cacti. Animal life includes insects, reptiles, birds, camels all of whom are adapted to the xeric (desert) conditions.
3. Deserts• Precipitation 20cm/year• Dry, sparce vegetation; scattered grasses• Parts of Africa, Asia, Australia, North America
Tropical deciduous forest: Dense bushes and shrubs rule here along with broad levels of trees. This type of forests is found in many parts of the world and large variety of flora and fauna are found here.
Deciduous forestsPrecipitation - 75-250cm/yearWarm summers, cool wintersEurope; NE United States;Eastern Canada
Aquatic Ecosystems An aquatic ecosystem is an ecosystem located in a body of water. It comprises aquatic fauna, flora and the properties of water too. There are two types of aquatic ecosystems, Marine and freshwater.
The Marine EcosystemMarine ecosystems are the largest ecosystems with coverage of nearly 71% of the Earths surface and containing 97% of the planets water. The water in Marine ecosystems has salts and minerals dissolved in them in high amounts. Different divisions of marine ecosystems are:
• Oceanic: The relatively shallow part of the ocean that lies over the continental shelf.• Profundal: Bottom or deep water.• Benthic Bottom substrates.• Inter-tidal: The area between high and low tides.
Salt marshesCoral reefsHydrothermal vents-where chemosyntheticbacteria form the food base.
Ocean Ecosystems:• Very large amount of Earth is covered by ocean (~75%)• 40% of all photosynthesis occurs in oceans.• 3 types of oceanic ecosystems• Shallow ocean waters• Deep ocean water• Deep ocean surface.
Deep ocean surface. –Photosynthetic plankton is base of food chain. –Only occurs in Deep ocean surface & Shallow ocean ecosystems –No photosynthesis can occur in deep ocean because light cannot penetrate deeply into water.
The Freshwater EcosystemIn contrast to the Marine ecosystem, freshwater ecosystems only cover 0.8% of the Earths surface and contain 0.009% of its total water. There are three basic types of freshwater ecosystems:
Freshwater EcosystemLentic: Still or slow-moving water like pools, ponds, and lakes.Lotic: Fast-moving water like streams and rivers.Wetlands: Places where the soil is saturated or inundated for at least some time.
Freshwater EcosystemThese ecosystems are home to amphibians, reptiles and almost 41% of world’s fish species. Faster moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow moving water of pools.
A freshwater ecosystem in GranCanaria, an island of the Canary Islands(Spain)
• Economic Benefits• The mangroves supply forestry products (firewood, charcoal, timber, honey• etc.) and fishery products (fish, prawn, crab, mollusk etc.). Due to high• calorific values, mangrove twigs are used for making charcoal and firewood.• One ton of mangrove firewood is equivalent to 5 tons of Indian coal, and it• burns producing high heat without generating smoke. The mangrove wood• with high content of tannin is used as timber for its durability. The• pneumatophores are used to make bottle stoppers and floats. Nypa leaves are• used to thatch roofs, mats and baskets. Shells of mangrove molluscs are used• to manufacture lime.
Importance of EcosystemsMangroves attract honey bees and facilitateapiculture activities in some areas. Forinstance, the Sundarbans provide employmentto 2000 people engaged in extracting 111 tons ofhoney annually and this accounts for about 90%of honey production among the mangroves ofIndia (Krishnamurthy, l990). In Bangladesh, anestimated 185 tons of honey and 44.4 tons ofwax are harvested each year in the western partof the mangrove forest (Siddiqi, l997).
The Importance of Ecosystems.Ecosystems are communities of living things andthe environmental features that support them.Ecosystems are essential to humanlife, providing us with innumerable andinvaluable services.These Ecosystem services arethe goods and services derived from naturaland managed ecosystems upon which humanwelfare depends, and include everything fromclean air and water to food and fuel.
The Importance of Ecosystems.Ecosystems are communities of living things and the Ecosystems are essential to humanlife, providing us with innumerable and invaluable services.These Ecosystem services are the goods and services derived from natural and managed ecosystems upon which human welfare depends, and include everything from clean air and water to food and fuel.
Mountain EcosystemHalf of the worlds population depends onmountain water An estimated one-tenth of the human population derive their life-support directly from mountains. Yet, mountains are important not only for their inhabitants, but for millions of people living in lowlands. At the global scale, mountains greatest value may be as sources of all the worlds major rivers, and many smaller ones (Mountain Agenda, 1998).
Mountain EcosystemMountain water is also a source of hydroelectric power, most of which is used on the plains below. Historically, water wheels have provided energy in mountain regions, mainly for grinding grain. In rural Nepal there are an estimated 25 000 water wheels and over 900 micro-hydropower turbines - a more recent technology - that provide a critical source of energy
Threats to the ecosystemThere are generally considered to be nine major threats to the stability of ecosystems on Earth. Climate change and loss of biodiversity are often the most publicised, although there are seven other factors that may be equally threatening.
Threats to EcosystemsThe spread of agriculture and other human activities into natural habitats poses a large threat to ecosystems. Similarly, the disruption of fresh water systems through damming and diversion by humans can lead to vast habitats becoming dry and barren(empty).
Threats to EcosystemsChemical pollution can have devastating effects of the health of ecosystems (as well as humans) and the release of aerosols into the atmosphere (through activities such as burning fossil fuels) damages ecosystems in numerous ways. The release of aerosols (among other things) can also lead to the depletion of the ozone layer which threatens to allow harmful solar radiation to cause damage to organisms and ecosystems.
Threats to EcosystemsAnother potential threat to global ecosystems that is the acidification of the oceans due to increased carbon dioxide in the atmosphere, which can have serious knock-on effects on important aspects of ocean chemistry.
Threats to Ecosystems1. Loss of crop & grazing land2. Depletion of worlds tropical forests3. Extinction of species4. Rapid population growth5. Shortage of fresh water resources6. Overfishing, habitat destruction, &pollution in the marine environment
Threats to Ecosystems7. Threats to human health8. Climate change9. Acid rain10. Pressures on energy resources
Main threats to ecosystems from human activitiesPopulation and consumption growth.Infrastructure development (dams, urban growth, highways).Land conversion (deforestation, agriculture, urban growth).Overharvesting and overexploitation (overfishing, wasteful irrigation).Release of pollutants (human waste, agricultural and industrial chemicals).Introduction of exotic species (replacing and overwhelming indigenous species).
River pollution• Every day, 2 million tons of human waste are disposed of in water courses.• 40% of water bodies assessed in 1998 in the United States were not deemed fit for World distribution of hydropower recreational use due to nutrient, metal and agricultural pollution.• 5 out of 55 rivers in Europe are considered pristine, and only the upper sections of the 14 largest rivers retain good ecological status.• In Asia, all rivers running through cities are badly polluted.
Impacts of waterways diversion and fragmentation• 60% of the worlds 227 largest rivers are severely fragmented by dams, diversions and canals, leading to the degradation of ecosystems.• In 1998, the Aral Sea had lost 75% of its total volume. Its demise was caused primarily by the diversion of the inflowing Amu Darya and Syr Darya rivers.
Wetlands loss• 50% of the worlds wetlands have been lost since 1900.• More than 80% of the wetlands along the Danube River have been destroyed since the start of the 20th century.• The Mesopotamian Marshlands in the Tigris and Euphrates river basins were devastated by damming and river channelisation.
Biodiversity loss• Between 34 and 80 fish species have become extinct since the late 19th century, 6 since 1970.• At a global level, around 24% of mammals and 12% of birds are classified as threatened.• In the United States, 120 of 822 freshwater fish species are considered threatened, representing 15% of total fish species.