Environmental Science
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Earth’s Ecosystems Ecology Ecology: Scientific study of the interactions between organisms and the environment Rediscovery of the nearly extinct harlequin toad in Costa Rica raises many ecological questions What environmental factors limit their geographic distribution? What factors (food, pathogens) affect population size? Ecological Research Areas of Ecological Research: Global Ecology: examines the influence of energy and materials on organisms across the biosphere Landscape Ecology: focuses on the exchanges of energy, materials, and organisms across multiple ecosystems Ecosystem Ecology: emphasizes energy flow and chemical cycling among the various biotic and abiotic components Community Ecology: deals with the whole array of interacting species in a community Population Ecology: focuses on factors affecting population size over time Organismal Ecology: studies how an organism’s structure, physiology, and (for animals) behavior meet environmental challenges Figure 52.2 Global ecology Landscape ecology Ecosystem ecology Community ecology Population ecology Organismal ecology Weather vs. Climate Weather: Local area’s short term temperature, precipitation, humidity, wind, cloud cover and other physical conditions of the atmosphere measured over hours or days Climate: Long-term prevailing weather conditions in an area Major components of climate are temperature, precipitation, sunlight, and wind Macroclimate: Consists of patterns on the global, regional, and landscape (multiple ecosystems) level Microclimate: Consists of very fine patterns, such as those encountered by the community of organisms underneath a fallen log Determined by fine-scale differences in the environment that affect light and wind patterns Water Currents Affect Climate Air Circulations Affect Climate Rain Shadow Effect The Earth’s surface affects climate. Biomes Biomes: Major life zones characterized by vegetation type (terrestrial biomes) or physical environment (aquatic biomes) Climate is very important in determining why terrestrial biomes are found in certain areas Climate affects the latitudinal patterns of terrestrial biomes Biomes are affected not just by average temperature and precipitation, but also by the pattern of temperature and precipitation through the year Leads to formation of tropical (hot), temperate (moderate) and polar (cold) regions – deserts, grasslands and forests Terrestrial Biomes: Often named for major physical or climatic factors and for vegetation Characterized by distribution, precipitation, temperature, plants, and animals Usually grade into each other, without sharp boundaries which may be wide or narrow Climb a tall mountain from its base to the summit, you’ll see changes as you might as you travel from the equator to the poles Figure 52.9 30°N Tropic of Cancer Equator Tropic of Capricorn 30°S Tropical forest Savanna Desert Chaparral Temperate grassland Temperate broadleaf forest Northern coniferous forest Tundra High mountains Polar ice Biomes Based on Elevation Biomes Similar characteristics can arise in distant biomes through Convergent Evolution For example, cacti in North America and euphorbs in African deserts appear similar but are from different evolutionary lineages Tropical Rain Forest Tropical Rain Forests: Hot temperature, moisture laden air rises resulting in constant rainfall (200 inches per year) Temperature is high year-round (25–29C) with little seasonal variation High Biodiversity: home to millions of animal species, including an estimated 5–30 million still unknown species of insects, spiders, and other arthropods 2% of the land but ½ of world’s species; single tree can have several thousand insect species Dominated by broadleaf evergreen plants; their dense tops block out most of the sun not reaching the forest floor Ground has little vegetation (those that do have large leaves); vines (lianas) grow on trees to reach the sun Little wind because of the dense vegetation; plants depend on bats, birds, bees and other species for pollination Rapid human population growth is now destroying many tropical forests Tropical Rain Forests Olinguito New mammal species in the cloud forests lining the Andes Mountains of South America - Olinguito and classified it in the Procyonidae family, the same as raccoons. Temperate Rain Forest Coastal Coniferous Forest or Temperate Rain Forests: Found in scattered coastal temperate areas that have ample rainfall or moisture from dense ocean fogs Douglass firs and redwoods Deserts Desert: Annual precipitation is low; often scattered unevenly throughout the year Heat of day bakes the earth causing evaporation of water from leaves and soil Soils have little vegetation and moisture to store the heat so you can roast during the day and freeze at night Tropical Deserts: Hot and dry most of the year; few plants and a hard wind blown surface of rocks and some sand Temperate Deserts: Daytime temperatures are high in the summer and low in winter; more precipitation than in the topical deserts; drought resistance vegetation - cacti Cold Deserts: Vegetation is sparse; winters are cold; summers warm or hot and precipitation is low; plants and animals have adapted to stay cool and get enough water Fragile Ecosystem: slow plant growth; low species diversity; slow nutrient recycling and lack of water Deserts Deserts Savannah Savannah Equatorial and subequatorial regions Warm temperatures year round with wet and dry seasons Precipitation is seasonal Temperature averages (24–29C) but is more seasonally variable than in the tropics Contains widely scattered clumps of trees (aracia with thorns to prevent being eaten) Grasses and make up most of the ground cover; fire-adapted and tolerant of seasonal drought Plants have adapted to survive drought and extreme heat Grazing animals (grass and herb eating; wildebeest) and browsing animals (twig and leaf eating; giraffe) along with predators (lion) Savannah Chaparral Chaparral: Occurs in mid-latitude coastal regions on several continents Summer is hot (30C+); fall, winter, and spring are cool (10–12C) Close to sea provides a slightly longer winter rainy season than nearby temperate deserts Precipitation is highly seasonal with rainy winters and dry summers Fogs in the spring and fall reducing evaporation Consist of dense growth of low growing evergreen shrubs and occasional small trees with leathery leaves to reduce evaporation Dominated by shrubs, small trees, grasses, and herbs; adapted to fire and drought Prone to fires in the dry season Many plants produce seeds that only germinated after a wildfire Animals include amphibians, birds, reptiles, insects, small mammals, and browsing mammals People like to live here because of its moderate, sunny climate with mild wet winters and warm dry summers; risk losing their homes to frequent fires and mud slides Chaparral Chaparral Temperate Grasslands Temperate Grassland Found on many continents Precipitation is highly seasonal Winters are cold (often below –10C) and dry; summers are hot (often near 30C) and dry Dominant plants are grasses and adapted to droughts and fire Little tree growth Large grazers such as bison and wild horses and small burrowers such as prairie dogs Most grasslands have been converted to farmland (Midwest) Temperate Grassland Mountains Mountains: Some of the world’s most spectacular environments are high on Mountains, steep or high lands that cover ¼ of the Earth’s surface; dramatic changes in altitude, slope, climate, soil and vegetation occur in a very short distance 1.2 bil people (18% of the world’s population) live on them or their edges; 4 bil (59%) depend on mountain systems for all or some of their water Majority of the world’s forests; habitats for biodiversity and contain endemic species found no where on Earth Help regulate the earth’s climate: mountains covered in ice and snow help to reflect solar radiation back into space helping to cool the plant and offset global warming Can affect sea levels: storing or releasing water in glaciers; as the earth warms, water can be released in oceans causing them to rise Major storehouses of water Despite their significance, mountain ecosystems are not a high priority for governments and/or environmental groups Mount Rainier National Park Forests Northern Coniferous Forest Northern Coniferous Forest or Taiga: Spans northern North America and Eurasia and is the largest terrestrial biome on Earth Cold forests are often found just south of Artic tundra and above certain altitudes in the High Sierras or Rockies Precipitation varies; some have periodic droughts and others, especially near coasts, are wet Winters are cold; summers may be hot (Siberia ranges from –50C to 20C) Subarctic climate: winters are long, dry and extremely cold; sunlight may only be available 6-8 hrs; summers are short, with cool to warm temperatures; sun shines 19 hrs Plant diversity is low as few species can survive the winters when soil moisture is frozen Conifers such as pine, spruce, fir, and hemlock dominate; conical shape of conifers prevents too much snow from accumulating and breaking their branches Migratory and resident birds; large mammals such as moose, brown bears, and Siberian tigers Northern Coniferous Forest Temperate Broadleaf Forest Temperate Broadleaf Forest: Found at midlatitudes in the Northern Hemisphere, with smaller areas in Chile, South Africa, Australia, and New Zealand Significant amounts of precipitation fall during all seasons as rain or snow Winters average 0C; summers are hot and humid (near 35C) Long warm summers, cold but not severe winters and abundant moisture, often fairly spread throughout the year Dominated by deciduous trees in the Northern Hemisphere; evergreen eucalyptus in Australia Broad-leaf trees: oak, hickory, maple and beech; survive cold winters by dropping their leaves in the fall and becoming dormant; each spring, new leaves form and turn colors in the fall Mammals, birds, and insects make use of all vertical layers in the forest Eastern US were home to bears, foxes and pumas (many have been killed) and the dominant mammal often is deer In the Northern Hemisphere, many mammals hibernate in the winter Impact of human activities: disturbed more than any other for growing of crops, wood or cities; within 100-200 years after it’s left undistributed, it can return to forest Temperate Broadleaf Forest Tundra Tundra: Covers expansive areas of the Arctic; alpine tundra exists on high mountaintops at all latitudes Precipitation is low in arctic tundra and higher in alpine tundra Winters are cold (below –30C); summers are relatively cool (less than 10C) Treeless and bitterly cold Swept by cold winds and covered by ice and snow Winters are long and dark Little precipitation Permafrost, a permanently frozen layer of soil, prevents water infiltration Vegetation is herbaceous (mosses, grasses, forbs, dwarf shrubs and trees, and lichen) and supports birds, grazers, and their predators; alpine can be flowers Most of the growth occurs in the 7-8 week summer when the sun shines almost 24 hrs Mammals include musk oxen, caribou, reindeer, bears, wolves, and foxes; many migratory bird species nest in the summer Tundra Water Earth is covered with water - known as the “Water Planet” Saltwater covers 71% of the Earth Freshwater 2.3% • Aquatic Life Zones: determined by the amount of salinity – amount of salt (NaCl) in the water Saltwater: Marine: brackish which is a combination of salt and freshwater and are considered to be saltwater and include Global ocean is a single and continuous body of water 4 oceans: Atlantic, Arctic, Indian and Pacific; Antarctic Oceans and estuaries, coastlands and shorelines, coral reefs and mangrove forests Freshwater Lakes, rivers and streams and inland wetlands Water Planet Aquatic Biomes Aquatic Biomes: Account for the largest part of the biosphere in terms of area Marine biomes have salt concentrations of about 3% Largest marine biome is made of oceans, which cover about 75% of Earth’s surface and have an enormous impact on the biosphere Freshwater biomes have salt concentrations of less than 0.1% Freshwater biomes are closely linked to soils and the biotic components of the surrounding terrestrial biome Stratified into Zones or layers defined by light penetration, temperature, and depth: Pelagic Zone: Photic Zone has sufficient light for photosynthesis; most animals live here Aphotic Zone receives little light; extensive with little life Deep in the Aphotic Zone lies the Abyssal Zone with a depth of 2,000 to 6,000 m Benthic Zone: Organic and inorganic sediment at the bottom of all aquatic zones Communities of organisms are collectively called the Benthos Detritus: Dead organic matter, falls from the productive surface water; important source of food Aquatic Biomes Figure 52.15 30°N Tropic of Cancer Equator Tropic of Capricorn 30°S Oceanic pelagic and benthic zones Intertidal zones Estuaries Coral reefs Rivers Lakes Lakes Lakes: Natural bodies of freshwater formed from precipitation, runoff or groundwater that fill in depressions in the surface caused by glaciers (Bear Mountain), volcanoes (Crater Lake) or other ways such as supplied with water from rain (precipitation) or streams Size varies from small ponds to very large lakes Oligotrophic Lakes: Nutrient-poor and generally oxygen-rich Small supply of plant nutrients Generally deep with steep banks; fed by glaciers and mountain streams with little sediment; crystal clear Eutrophic Lakes: Nutrient-rich and often depleted of oxygen if ice covered in winter Rooted and floating aquatic plants live in shallow and well-lighted area close to shore Water is too deep to support rooted aquatic plants; small drifting animals called zooplankton graze on the phytoplankton Invertebrates live in the benthic zone; Fishes live in all zones with sufficient oxygen Lakes Lakes Wetlands Surface Water: precipitation that does not sink into the ground or evaporate Runoff: precipitation that runs into a stream Watershed, Drainage Basin: land that delivers runoff, sediment and dissolved substances into a stream; small streams form rivers and rivers flow downhill to the ocean Aquatic Life Zones: Source Zone: Headwaters or mountain highland streams; usually shallow, cold, clear and swift flowing; waterfalls and rapids Not productive because of lack of nutrients and producers; food is from decomposition; algae; fishes Transition Zone: Middle; become wider, deeper and warmer; slower; more turbid (cloudier) Producers; both cold and warm water fish (black bass) Floodplain Zone: Over time, they shape the land including leveling or cutting through mountains forming canyons; streams can join others, forming wider and deeper rivers Large amount of producers and fish; rivers end in a mouth or delta; absorb the floodwaters and add nutrient rich land Human Activity Human activities are disrupting and degrading many of the ecological and economic services provided by fresh water rivers, lakes and wetlands: Dams and Canals on rivers fragment about 40% of the world’s 237 large rivers Alter or destroy aquatic wildlife habitats by reducing water flow and increasing damage from coastal storms Flood Control Levees and Dikes: Built along rivers and disconnect the rivers from their floodplains Destroy aquatic habitats and alter or reduce the function of nearby wetlands Hinders the spawning cycle of fishes and birds and can disrupt food chains; species are lost and the biodiversity is threatened Interrupts sediment flow and distribution Pollutants from cities and farms add excess nutrients causing algal explosions (blooms) and depleting the oxygen Wetlands have been drained or filled to grow crops or covered to build buildings or roads Wetlands Wetlands Wetlands Habitat that is inundated by water at least some of the time and that supports plants adapted to water-saturated soil High organic production and decomposition and have low dissolved oxygen content Can develop in shallow basins, along flooded river banks, or on coasts of large lakes and seas Wetlands are among the most productive biomes on Earth Plants include lilies, cattails, sedges, tamarack, and black spruce Wetlands are home to diverse invertebrates and birds, as well as otters, frogs, and alligators Humans have destroyed up to 90% of wetlands; wetlands purify water and reduce flooding Wetlands Restoration of Wetlands Streams and Rivers Streams and Rivers: Most prominent physical characteristic of streams and rivers is current Headwaters are generally cold, clear, turbulent, swift, and oxygenrich; they are often narrow and rocky Downstream waters form rivers and are generally warmer, more turbid, and more oxygenated; they are often wide and meandering and have silty bottoms May contain phytoplankton or rooted aquatic plants Diversity of fishes and invertebrates inhabit unpolluted rivers and streams Damming and flood control impair natural functioning of stream and river ecosystems Streams and Rivers Coastal Wetlands Estuaries: Where rivers meet the sea; partially enclosed bodies of water where sea water mixes with fresh water as well as nutrients from streams, rivers and runoff from the land Coastal Wetlands: Coastal land areas covered with water all or part of the year Combined with Estuaries, they are some of the Earth’s most productive ecosystems because of nutrients, rapid flow of water and ample sunlight: Estuaries and Coastal Wetlands: include river mouths, inlets, bays, sounds, salt marshes and mangrove forests Seagrass Beds: Species of plants that grow underwater in shallow marine and estuaries along the coastline Highly productive and support a variety of marine species Stabilize shorelines and reduce wave impact Life is harsh; adapt to daily and seasonal changes in tidal and river flow; water temperatures and salinity; and runoff from the land including soil sediment and pollutants; because of this, they may have low plant diversity but high productivity Coastal Wetlands Mangrove Forests: Found along 70% of gently sloping sandy and silt coastlines in the tropics and sub-tropics Grow in salt water and have extensive root systems that can support during changes in water levels Coastal Aquatic Systems provide important ecological and economic services: Maintain water quality by filtering toxic pollutants, excess plant nutrients, sediments and absorb other pollutants Provide food, habitats and nursery sites Reduce storm damage and coast erosion by absorbing waves and storing excess water produced by storms and tsunamis Provide timber and wood for fuel UN estimates that between 1980 and 2005 at least 1/5 of the mangrove forests were lost due mainly to human coastal development Loss of mangroves can lead to polluted drinking water caused by inland intrusion of saltwater into fresh water aquifers used to supply drinking water River Delta Estuaries Mangrove Trees Life in Coastal Wetlands Coastal Shoreline Intertidal Zone: Area between high and low tides (gravitational pull of the moon and sun) Organisms must adapt to movement of water; high tides to drying out at low tides Oxygen and nutrient levels are high Deal with daily salinity and moisture changes Organisms need to “hold on”: Rocky Shores: Pounded daily by waves Numerous pools and other habitats with a great variety of species; marine algae Animals have adapted to attach themselves to the hard surface Sandy Shores: Barrier beaches Many organisms are hidden from view by burrowing, digging or tunneling in the sand; home to shore birds that feed on crustaceans – sea grass and algae Barrier Islands: Narrow islands that form offshore parallel to the coast Intertidal Zones Life Along the Coast Importance of Sand Dunes Importance of Sand Dunes: Sand is held in place by plant roots 1st line of defense against the sea Often removed by developers; and when large storms hit and cause damage, they are incorrectly called “Natural Disasters” Oceanic Pelagic Zone Oceanic Pelagic Zone: Constantly mixed by wind-driven oceanic currents Oxygen levels are high Turnover in temperate oceans renews nutrients in the photic zones; year-round stratification in tropical oceans leads to lower nutrient concentrations Biome covers approximately 70% of Earth’s surface Phytoplankton and zooplankton are the dominant organisms in this biome; also found are free-swimming animals Zooplankton includes protists, worms, copepods, krill, jellies, and invertebrate larvae Other animals include squids, fishes, sea turtles, and marine mammals Oceanic Pelagic Zone Coral Reefs Coral Reefs: World’s oldest, most diverse and most productive ecosystem Known as “Natural Wonders” Biodiversity – marine equivalent of Tropical Rain Forests Formed by tiny animals known as polyps – jellyfish; calcium carbonate Occupy only 0.2% of the ocean’s floor 15% have been destroyed and another 20% damaged They provide important ecological and economic services; Moderate atmospheric temperatures Act as natural barriers protecting coasts from erosion Provide habitats Support fishing and tourism businesses Provide jobs and building materials Coral Reefs Life on a Coral Reef Death of a Coral Reef Marine Benthic Zone Marine Benthic Zone: Consists of the seafloor below the surface waters of the coastal zone Organisms in the very deep benthic zone are adapted to continuous cold and extremely high water pressure Mainly soft sediments; some areas are rocky Shallow areas contain seaweeds and filamentous algae Deep-sea hydrothermal vents of volcanic origin on mid-oceanic ridges are surrounded by unique chemoautotrophic prokaryotes, as well as echinoderms and arthropods Benthic communities include invertebrates and fishes Marine Benthic Zone Human Problem Human activities are causing major threats to marine systems, especially coastal wetlands, shore lands, mangrove forests and coral reefs; threatened by man is the biological diversity and ecosystems provided by the oceans that cover 71% of Earth: Coastal Development: by 2006, 46% of the world’s population (more than ½ of US) lived along or near coasts; by 2040, up to 80% may Overfishing: depletes population of commercial fish Pollution: fertilizers or animal waste; sewage from ships; oil spillage Habitat Destruction: development but also, trawler fishing Introduction of Invasive Species (non-native) Climate Change from Human Activities: rise in levels Pollution of coastal wetlands and estuaries
