Terrestrial Ecosystems

Definition of Terrestrial Ecosystems

An ecosystem is a collection of communities of both living and nonliving things that are interrelated. While many ecosystems exist on land and in the waters of the world; terrestrial ecosystems are those that are found only on land. The biotic, or living things found in an ecosystem, include various life forms, such as plants and animals. The abiotic, or non-living things found in an ecosystem include the various land-forms and the climate.

Types and Examples of Terrestrial Ecosystems

While there have been many classification schemes developed over time it is now generally accepted that there are six types of terrestrial ecosystems. These include taiga, tundra, deciduous forest, grasslands, tropical rain forests, and deserts.

Taigas are cold-climate forests found in the northern latitudes. Taigas are the world's largest terrestrial ecosystem and account for about 29% of the earth's forests. The largest taiga ecosystems are found in Canada and Russia. Taigas are known for their sub-arctic climate with extremely cold winters and mild summers. They primarily consist of coniferous trees, such as pines, although there are some other deciduous trees, such as spruce and elm, that have adapted to live in these areas that receive little direct sunlight for much of the year. Taigas are home to large herbivores such as moose, elk, and bison as well as omnivores such as bears.

The tundra ecosystems of the world are primarily found north of the Arctic Circle. They consist of short vegetation and essentially no trees. The soil is frozen and covered with permafrost for a large portion of the year. Caribou, polar bears, and musk ox are some of the notable species who call the tundra home

Deciduous forest ecosystems make up the eastern half of North America and a large portion of Europe. They typically have an average yearly temperature of fifty degrees Fahrenheit, and they average about 30-60 inches of rain per year. These forests are inhabited by a variety of wildlife including deer, bear, foxes, as well as numerous species of trees, shrubs, and flowers. If you live in or have ever traveled to the eastern United States you have been to a deciduous forest.

Grasslands are also known as the plains and prairies. If you imagine the wild west with tumbleweeds blowing across the plains and large herds of deer and buffalo you are imagining the grasslands. These ecosystems are characterized by 20-35 inches of rain per year and a predominant covering of various species of grasses. They are also known for their very rich soil.

Tropical rain forest ecosystems have the greatest diversity of plants and animals of all of the ecosystems. They exist 28 degrees north or south of the equator and are known for their high average temperatures as well as a significant amount of rainfall. The lush forests of the Amazon in South America are classic examples of tropical rain forest.

Close your eyes and imagine walking through mountainous dunes of sand as the blistering sun parches your mouth as you search for water. This scene gives you a look at the final terrestrial ecosystem which is the desert. These ecosystems are hot and dry with very little vegetation and very few species of animals that call them home other than reptiles, arachnids, and birds. The large Saharan desert takes up much of the northern part of the African continent.

Summary of Terrestrial Ecosystems

As you can see, all ecosystems that exist entirely on land are terrestrial ecosystems. They range from the coldest places on earth at the extreme northern latitudes to the hottest deserts found around the equator. Each ecosystem is inhabited by species of plants and animals that have evolved to thrive in them.

Aquatic Ecosystem

An aquatic ecosystem is an ecosystem located in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.^[1]

Types

Marine

Marine ecosystems cover approximately 71% of the Earth's surface and contain approximately 97% of the planet's water. They generate 32% of the world's net primary production.^[1] They are distinguished from freshwater ecosystems by the presence of dissolved compounds, especially salts, in the water. Approximately 85% of the dissolved materials in seawater are sodium and chlorine. Seawater has an average salinity of 35 parts per thousand (ppt) of water. Actual salinity varies among different marine ecosystems.
Marine ecosystems can be divided into the following zones: oceanic (the relatively shallow part of the ocean that lies over the continental shelf); profundal (bottom or deep water); benthic (bottom substrates); intertidal (the area between high and low tides); estuaries; salt marshes; coral reefs; and hydrothermal vents (where chemosynthetic sulfur bacteria form the food base).
Classes of organisms found in marine ecosystems include brown algae, dinoflagellates, corals, cephalopods, echinoderms, and sharks. Fish caught in marine ecosystems are the biggest source of commercial foods obtained from wild populations.
Environmental problems concerning marine ecosystems include unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, climate change, and building on coastal areas.

Freshwater

Freshwater ecosystems cover 0.8% of the Earth's surface and contain 0.009% of its total water. They generate nearly 3% of its net primary production. Freshwater ecosystems contain 41% of the world's known fish species.
There are three basic types of freshwater ecosystems:

• Lentic: slow-moving water, including pools, ponds, and lakes.
• Lotic: rapidly-moving water, for example streams and rivers.
• Wetlands: areas where the soil is saturated or inundated for at least part of the time.^[4]

Lake ecosystems can be divided into zones: pelagic (open offshore waters); profundal; littoral (nearshore shallow waters); and riparian (the area of land bordering a body of water). Two important subclasses of lakes are ponds, which typically are small lakes that intergrade with wetlands, and water reservoirs. Many lakes, or bays within them, gradually become enriched by nutrients and fill in with organic sediments, a process called eutrophication. Eutrophication is accelerated by human activity within the water catchment area of the lake.
The major zones in river ecosystems are determined by the river bed's gradient or by the velocity of the current. Faster moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow moving water of pools. These distinctions forms the basis for the division of rivers into upland and lowland rivers. The food base of streams within riparian forests is mostly derived from the trees, but wider streams and those that lack a canopy derive the majority of their food base from algae. Anadromous fish are also an important source of nutrients. Environmental threats to rivers include loss of water, dams, chemical pollution and introduced species.
Wetlands are dominated by vascular plants that have adapted to saturated soil. Wetlands are the most productive natural ecosystems because of the proximity of water and soil. Due to their productivity, wetlands are often converted into dry land with dykes and drains and used for agricultural purposes. Their closeness to lakes and rivers means that they are often developed for human settlement.

Ponds

These are a specific type of freshwater ecosystems that are largely based on the autotroph algae which provide the base trophic level for all life in the area. The largest predator in a pond ecosystem will normally be a fish and in-between range smaller insects and microorganisms. It may have a scale of organisms from small bacteria to big creatures like water snakes, beetles, water bugs, frogs, tadpoles, and turtles. This is important for the environment.

Functions

Aquatic ecosystems perform many important environmental functions. For example, they recycle nutrients, purify water, attenuate floods, recharge ground water and provide habitats for wildlife. Aquatic ecosystems are also used for human recreation, and are very important to the tourism industry, especially in coastal regions.
The health of an aquatic ecosystem is degraded when the ecosystem's ability to absorb a stress has been exceeded. A stress on an aquatic ecosystem can be a result of physical, chemical or biological alterations of the environment. Physical alterations include changes in water temperature, water flow and light availability. Chemical alterations include changes in the loading rates of biostimulatory nutrients, oxygen consuming materials, and toxins. Biological alterations include the introduction of exotic species. Human populations can impose excessive stresses on aquatic ecosystems.

Abiotic characteristics

An ecosystem is composed of biotic communities and abiotic environmental factors, which form a self-regulating and self-sustaining unit. Abiotic environmental factors of aquatic ecosystems include temperature, salinity, and flow.
The amount of dissolved oxygen in a water body is frequently the key substance in determining the extent and kinds of organic life in the water body. Fish need dissolved oxygen to survive. Conversely, oxygen is fatal to many kinds of anaerobic bacteria.
The salinity of the water body is also a determining factor in the kinds of species found in the water body. Organisms in marine ecosystems tolerate salinity, while many freshwater organisms are intolerant of salt. Freshwater used for irrigation purposes often absorb levels of salt that are harmful to freshwater organisms.Though some salt can be good for organisms.

Biotic characteristics

The organisms (also called biota) found in aquatic ecosystems are either autotrophic or heterotrophic.

Autotrophic organisms

Autotrophic organisms are producers that generate organic compounds from inorganic material. Algae use solar energy to generate biomass from carbon dioxide and are the most important autotrophic organisms in aquatic environments.^[6] Chemosynthetic bacteria are found in benthic marine ecosystems. These organisms are able to feed on hydrogen sulfide in water that comes from volcanic vents. Great concentrations of animals that feed on this bacteria are found around volcanic vents. For example, there are giant tube worms (Riftia pachyptila) 1.5m in length and clams (Calyptogena magnifica) 30cm long.^[7]

Heterotrophic organisms

Heterotrophic organisms consume autotrophic organisms and use the organic compounds in their bodies as energy sources and as raw materials to create their own biomass.^[6] Euryhaline organisms are salt tolerant and can survive in marine ecosystems, while stenohaline or salt intolerant species can only live in freshwater environments
Pollution is the process whereby various harmful substances are added to the environment (land, water, air etc.) by human and natural activities.

The various types of pollution that exist are:

* air pollution
* water pollution
* land pollution
* noise pollution

Natural activities that cause pollution are, for example, volcanic eruptions, sandstorms and natural forest fires. These events cause a large amount of substances such as ash and dust, which are harmful to our health, to be added to the environment.

Although some natural events may contribute to pollution, human activities have a more harmful impact to the environment.

How do humans contribute to pollution?

As the world population increases rapidly, there is an increasing demand for food, materials and energy. The activities that produce these products tend to pollute the environment.

DOMESTIC ACTIVITIES
Homes and offices produce a lot of rubbish and sewage every day.

INDUSTRIAL ACTIVITIES
Some by-products of industries are highly hazardous e.g. sulphur dioxide.

AGRICULTURAL ACTIVITIES
Farms, too, produce a lot of waste. Waste from animals, pesticides and herbicides are washed into rivers and then into the sea.

How does pollution affect our environment?

Pollution has adverse effects on all living and non-living things.

Some of these effects are:

EFFECTS ON MAN
Air pollution can cause breathing problems and eye, throat and skin irritation. When solid waste is not properly treated and disposed of, it can become a breeding for pests and disease can spread.

EFFECTS ON PLANTS
Leaves find it difficult to manufacture food in polluted air. When trees begin to lose their leaves, they may eventually die. When there is too much chemical content in the water absorbed by the roots, it can also affect plant life.

EFFECTS ON ANIMALS
Oil spills in the seas and oceans result in birds and animals (e.g. penguins and seals) being coated in oil. This makes it difficult for them to float and keep warm and they may eventually die. Solid waste in the water encourages the growth of algae which depletes water of oxygen and kills marine life.

EFFECTS ON BUILDINGS
Air pollution discolours and corrodes buildings and statues, e.g. the Louvre Museum in France, historical buildings in London and the Taj Mahal in India are all covered with a layer of pollutants.

~ Air Pollution

Air pollution refers to the discharge of harmful gases and dust into the atmosphere. When these harmful substances enter the air around us, they may cause irreversible damage to humans and to our environment.

Some of the main air pollutants are:

* Sulphur dioxide (SO2)
* Carbon monoxide (CO)
* Ozone (O3)
* Nitrogen dioxide (NO2)

So, what about those gases?

SULPHUR DIOXIDE
Responsible for acid rain.

CARBON MONOXIDE
Enters the blood stream and reduces the delivery of oxygen to the body's organs and tissues.
Elevated levels of CO may result in impairment of visual perception, work capacity, manual dexterity, learning ability and performance of complex tasks.

OZONE
Damage to lung tissues and reduces lung functioning.
Reduces agricultural crop yield; causes foliar damage in many crops and trees.