BIODIVERSITY: Ecosystem Diversity
Ecosystem diversity is the variety of habitats, the communities found in a geographic location, the beneficial services they provide for human populations, and the processes that support the ecosystem.
Earth is made up of land (terrestrial) and water (aquatic) environments. Within them, we find six main types of ecosystems: forest, grassland, tundra, and desert are found on the land. Freshwater and marine ecosystems are found in the earth’s waters.
They vary in biological communities due to differences in the abiotic factors present there. Each ecosystem is connected to the other because certain biotic and abiotic factors can move between ecosystems, like nutrients, organisms, water, and air. As a result, changes to one ecosystem can lead to changes in another. This is similar to the impact of the loss of a species in a community.
An example of how ecosystems are interconnected can be seen in the lifecycle of salmon. Baby salmon are born in freshwater streams. As they grow in size and strength, the salmon migrate toward the ocean where they obtain nutrients that allow them to grow large enough to make the journey back to their original breeding ground. At the end of their journey, and after breeding and spawning, they die. Their bodies provide the nutrients they gained from the ocean to the small freshwater streams. These benefits are even passed on to the surrounding terrestrial ecosystems, enriching the soils and life present there.
TYPES OF ECOSYSTEMS
Let’s take a look at the different types of ecosystems and what they contribute to the processes of our planet that support all life on Earth.
Found on land, terrestrial ecosystems vary in design due to variations in temperature, precipitation (amount of rainfall), soil composition, and the amount of light present. These factors influence the type of biotic community of species that can inhabit that area.
Forests are dominated by trees that interlock at the top creating a canopy that maintains moist and cooler temperatures within. Forests cover around 31% of the earth’s land surface, house 80% of terrestrial animal, plant, and insect species, and are key components to many of the ecosystem services that we receive and utilize.
There are three main types of forest ecosystems:
Tropical forests exist close to the equator, where exposure to sunlight and rainfall are at their highest, and are some of the most biologically diverse ecosystems on the planet. Also known as “the lungs of our planet,” they cover 7% of the land and provide 20% of the whole planet’s oxygen.
Temperate forests are found between the tropics and the polar regions of our planet. They are exposed to warm and cold air temperatures, which create the 4 seasons: spring, summer, autumn, and winter. Critical to the support of water, nitrogen, and carbon cycles, they are home to some of the oldest and largest organisms on the planet.
Boreal forests cover 33% of the land, circle the Northern Hemisphere, and sit just south of the arctic circle. The biodiversity found here is exposed to cold temperatures for most of the year. The boreal forests of Canada contain 300 billion tons of carbon, both above and below ground, which is the amount the world emits over a 36-year period.
It is estimated that globally the benefits we receive from forest services and processes are in excess of $4.7 trillion per year.
Grasslands are large open areas of land dominated by grasses and herbaceous non-woody plants with the occasional shrubs and trees. Covering around one-third of the earth’s land mass, low levels of rainfall, grazing animals, and wildfires maintain the landscape from developing into a forest. Due to the deep root systems of this vegetation, grassland ecosystems store 20–34% of global terrestrial carbon stocks.
Savannas are found closer to the equator than temperate grassland; they experience seasonal rainfall creating wet seasons during summer and dry seasons in the winter. The African savannah covers 50% of the continent and is a vital resource for the millions of people that live there. They rely on it for food production, wood fuel, and the grazing of livestock.
Temperate grasslands offer flat land with fertile soil. Such conditions are perfect for farming, which has led to almost 80% of grassland being converted to agricultural lands. Native prairie grasses have extremely long roots that can reach up to 10 feet deep, which are specially designed to protect them from winds, drought, and fires. Around these roots is a substance called glomalin, which is where the plants can store vast quantities of carbon.
Studies reveal that grassland services and processes across the globe provide a combined economic value of $20.8 trillion per year.
Tundra ecosystems are cold and windy treeless areas that are exposed to extreme temperatures of 21° to -29°F (-6° to -34° C) and with minimal rainfall. Tundra ecosystems can be found in the arctic circle or on the tops of mountains where snow exists for most of the year before summer brings warmth and days of 24-hour sunlight. It is an indicator ecosystem—that is, it is an ecosystem that demonstrates the health of the overall planet in terms of climate change.
Alpine tundra ecosystems are found above 11,000 feet on mountain ranges easily identified by the tree line of forests. Cold winds and minimal rainfall, along with thin layers of soil, restrict trees from becoming established. Small depressions, exposure to the sun, and the presence of soil create microhabitats where different species can become established in the same ecosystem. Species here are adapted to these conditions. Plants are low-growing, contain hairs for insulation, and even change color to control the amount of sunlight they can absorb. The Rocky Mountain alpine tundra in North America is an important ecosystem for elk, for instance. They migrate to this environment during winter where they can find important food sources to survive for the season.
Arctic tundra ecosystems are found between the taiga forests in the northern hemisphere and the polar ice caps. The most extreme temperatures recorded here are 61°F (16°C) in summer and -94°F (-70°C) in winter. Winters can last up to 10 months. These conditions limit the levels of biodiversity present; however, almost 2,000 plant species have found a way to live in this place. Migratory birds and caribou come here in the summer months and leave before winter. Few animal species make the arctic tundra their permanent home. It is a vital ecosystem for carbon storage, which impacts every person on the planet. Permafrost is a freezer for carbon found just below the surface layer of soil in tundra ecosystems. Year-round, the soil stays frozen preventing its release into the atmosphere. Scientists study the permafrost to identify past changes in our climate.
The estimated value of ecosystem services for the tundra is $261 billion. (This value excludes the Antarctic and Alpine ecosystems, as data are not available for these regions, so the actual value is expected to be higher.)
Deserts are extreme environments with temperatures reaching >122°F (>50°C) in the day and 25°F (-4°C) at night. Porous soils, minimal rainfall of fewer than 20 inches (50 cm), and the limited availability of nutrients create slow plant growth minimizing the amount of biodiversity present. Yet some species have adapted to such abiotic factors. They make up one-fifth of the earth’s land cover, can be found on every continent, and are home to one billion people. As desolate as they seem, deserts offer plenty of vital resources that humans use every day.
Arid deserts are mostly found around the equator due to the high level of sun exposure. They are hot and dry places containing sand dunes and occasional hospitable oases that can support any animals that inhabit the area. The Great Sandy Desert of Australia is a huge resource for minerals and metals due to the concentrated deposits left from water evaporation. It contains lead, uranium, iron ore, gold, and silver, all of which have multiple purposes and applications.
Semi-arid deserts are less hostile than the conditions of arid deserts. Daytime temperatures rarely exceed 100°F (38°C) and evenings cool to around 50°F (10°C). The cool nights create condensation from the day, adding to the moisture content of the land and allowing for more biodiversity to grow. Deserts can be climatically hot, as we all think of the deserts of Africa or Australia, for example, or climatically cooler like those found mostly in the Nearctic regions (North America, Greenland, Europe, Newfoundland, Russia, and northern Asia). They are excellent indicators for tracking climate change and desertification. Plants in Africa’s Kalahari Desert are being studied to understand the positive feedback process that reverts nutrients and organic matter from poor soils into fertile lands using plants adapted to desert environments. Their ability to collect and store water and nutrients creates microenvironments that can support other plants.
Coastal deserts are located near large water sources, such as oceans and seas. They are the most hospitable deserts due to their less extreme average temperatures of 75°F (24°C) in summer and 41°(5°C) in winter. Mountain ranges restrict rainfall to the area, but the soils are better at holding water from the fog that rolls in from the water bodies. The Namib Desert of Africa is the world’s oldest at 55 million years old. It is a vital economic resource for tungsten, salt, and diamonds, as well as home to two of Earth’s 36 ecological hotspots. Ecological hotspots are biogeographic regions with significant levels of biodiversity that are under threat from humans.
A valuation of desert ecosystems cannot be provided as there is little data on the value of their ecosystem services to date. But think about the services listed below and the monetary value that is associated with them, like oil, diamonds, and metals used in technology.
Aquatic ecosystems are found in Earth’s water environments. They are defined as: freshwater, which are bodies of water found inland and contain low to no levels of salt; and marine, which are generally found in the ocean where salt water content is higher. Specific ecosystems in each type are classified by the changes in temperature, depth, water flow, sunlight, salinity, and water acidity, and both of these ecosystems are intrinsically interconnected.
Freshwater ecosystems make up less than 3% of Earth’s global water supply and more than half is not available for consumption because they are frozen in glacial sheets, are atmospheric, or are too far beneath the surface of the Earth to be accessed. The low salt content of freshwater provides a habitat for many species to thrive. All life on earth needs water to survive. It is connected to every ecosystem on our planet through the hydrological cycle, also called the water cycle.
Ponds and lakes are still bodies of water, unlike rivers and streams, which transport water from mountains to the ocean connecting lakes and ponds above and below ground. Their size can vary from small backyard ponds to the Great Lakes of North America, which provide essential drinking water, resources for food production, and support for the ecosystem processes needed to keep our planet healthy. The Great Lakes contain 20% of the global surface freshwater supply. Products extracted from these lakes reach $4.1 trillion USD.
Streams and rivers are constantly moving bodies of water that are continually fed by the hydrological cycle transporting water vapor through the air in clouds which are released on land. In the mountains, water collects and travels down forming streams, carrying minerals and nutrients from the rocks to lakes, ponds, and wetlands habitats along the way. Ultimately, it ends up in the ocean, where the cycle continues. We have found ways to utilize this natural ecosystem to create power from its water flow, which we use to power cities.
Wetlands, as the name states, are areas of land covered in or saturated by water from nearby water sources or underground aquifers. Due to the high amounts of water and soil available, these habitats can support an immense variety of terrestrial and aquatic species which, in turn, then support more species in the surrounding ecosystems. Regarded as “the kidneys of our planet,” they contribute hugely to the regulating processes of Earth. The Pantanal wetlands are found in the heart of South America. Larger than England, this wetland supports 1.2 million people. The ecosystem services it provides are valued at $112 billion dollars each year.
Researchers have studied and identified all the ecosystem services connected to freshwater ecosystems and assigned them a total economic value of $14.9 trillion.
Marine ecosystems contain high levels of dissolved salt and span from coastal waters to the depths of the open ocean. Factors that influence marine ecosystems are light, nutrients, temperature depth, level of salinity, and topography. The composition of these factors controls the community of species found in these ecosystems and the ecosystem services they provide.
Estuaries are found at the mouth of rivers where freshwater meets seawater to create brackish water. Brackish water has more salinity (salt) than freshwater, but not as much as seawater. It is somewhere in between. Landforms protect the estuary from ocean waves, providing a safe habitat for many marine species that use this place as a nursery. It is also an integral part of many commercial marine species’ life cycles. Due to the influx of nutrients from rivers and the constant change in salinity from the tides, many species inhabit these ecosystems. The diverse plant life present assists in trapping sediment and removing pollutants before they reach the ocean.
Salt marshes are a type of wetland that experiences flooding from saltwater tides and are generally found near estuaries. They can be found on almost every coast around the world. The saline water limits the diversity of species, but the salt marshes play an important role in protecting land loss from erosion. They act as a protective barrier between inhabitable land and sea.
Mangroves are coastal ecosystems that are found in tropical and subtropical parts of the world. They are characterized by mangrove trees, which can thrive in saline waters. This irreplaceable habitat provides shoreline protection, offers a nursery for many marine species, and acts as a nesting site for birds. During Hurricane Irma in 2017, the presence of mangrove trees dampened the tidal surges in its path, protecting 500,000 people and saving $1.5 million in damages.
Coral Reefs are fascinating ecosystems that are created by living organisms called “polyps,” which are related to jellyfish. Some species are hard corals which create the beautiful coral reefs you see underwater, others are soft corals, which look like plants. They generally exist close to the ocean’s surface where sunlight can reach them. They provide an exceptional habitat for marine fish—25% of all marine fish use coral reefs during some part of their life cycle.
Seagrass beds are related to the flowering plants found on land. They can be found in saline or brackish waters around the world. Regarded as “the lungs of the sea,” they can generate more than 10 quarts (10 liters) of oxygen per square mile (2.6 km²), purifying water, absorbing nutrients, and preventing sand buildup in coral reefs by trapping sediment.
Open oceans are the largest ecosystems on our planet. They are found beyond the coasts and coastal marine ecosystems. The ocean propels many of Earth’s processes, such as climate and weather, through the absorption of solar radiation and currents. It transfers and redistributes heat to cool the planet. The ocean produces 50–80% of the earth’s oxygen with the help of inhabitants such as algae, phytoplankton, and bacteria.
Deep sea oceans are located .62 miles (1,000 m) below sea level and can continue on for another 6.2 miles (10,000 m). This ecosystem does not receive any sunlight from the surface. Temperatures are around freezing and water pressure increases with depth from 40 to more than 110 times the pressure found on the Earth’s surface. Connected to the open ocean as well as the atmosphere, the deep seafloor is made up of mud and decomposed organisms known as “ooze.” This sediment provides excellent carbon storage. As carbon dissolves from the atmosphere into the open ocean, it binds to molecules. As the water cools, the carbon is pulled down into the depths of the ocean where it can be stored for thousands of years.
Just under half of the world’s population (3 billion) directly relies on the resources our oceans provide, including more than 350 million jobs, creating a global economic value of $3–6 trillion each year.
Genetic diversity provides a vast range of characteristics that ensure the survival of a species when environmental changes occur, in turn supporting species diversity and the interactions of that community and ensuring their ability to perform their roles in their ecological niches.
In each ecosystem, different species are adapted to survive the environmental conditions present there. All inhabitants of planet Earth rely on the balance of life in each of these unique environments.
Having learned how species support the health of their ecosystems—and how ecosystems are interconnected with each other—and having covered some of the important ecosystem services they provide to us, we are going to take a look at biodiversity hotspots.
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