Lecture 14

Movement corridors

A movement corridor is a narrow strip of habitat connecting otherwise isolated patches Movement corridors promote dispersal and help sustain populations

extinction vortex

A small population is prone to inbreeding and genetic drift, which draw it down an extinction vortex The key factor driving the extinction vortex is loss of the genetic variation necessary to enable evolutionary responses to environmental change. Populations of the greater prairie chicken were fragmented by agriculture and later found to exhibit decreased fertility in Illinois To test the extinction vortex hypothesis, scientists imported genetic variation by transplanting birds from larger populations 01970 1975 1980 1985 1990 1995 Year (a) Population dynamics 100 90 80 70 60 50 40 The declining population rebounded, confirming that low genetic variation had been causing an extinction vortex

biological augmentation

Biological augmentation uses organisms to add essential materials to a degraded ecosystem Nitrogen-fixing plants can increase the available nitrogen in soil in mining sites Adding mycorrhizal fungi can help plants access nutrients from soil, enhancing recovery of native species The long-term objective of restoration is to return an ecosystem as much as possible to its pre-disturbance state Restoring the physical structure and plant community of an ecosystem may or may not lead to recolonization of animal species Biologists may also release animals to the ecosystem, or establish habitat corridors to facilitate animal migration. Damming and water diversion reduced water flow of Truckee River, leading to decline of riverside forests Ecologists worked with water managers to release sufficient water during the short season of seed release of cottonwood and willow trees Nine years of controlled flow release led to dramatic recovery of cottonwood- willow riparian forest

bioremediation

Bioremediation is the use of organisms to detoxify ecosystems The organisms most often used are prokaryotes, fungi, or plants, which can take up, and sometimes metabolize, toxic molecules The bacterium Shewanella oneidensis can metabolize uranium and other elements to insoluble forms that are less likely to leach into streams and groundwater

the carbon cycle

Carbon-based organic molecules are essential to all organisms Photosynthetic organisms convert CO2 to organic molecules that are used by heterotrophs Carbon reservoirs include fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, the atmosphere, and sedimentary rocks CO2 is taken up and released through photosynthesis and respiration; additionally, volcanoes and the burning of fossil fuels contribute CO2 to the atmosphere

conversation biology

Conservation biology has attempted to sustain the biodiversity of entire communities, ecosystems, and landscapes The structure of a landscape, such as fragmentation and edges, can strongly influence biodiversity

ecosystem services

Ecosystem services encompass all the processes through which natural ecosystems and their species help sustain human life Purification of air and water Detoxification and decomposition of wastes Cycling of nutrients Moderation of weather extremes. In 1993, ecologist Robert Costanza proposed to add money value to ecosystem services, and estimated the value of Earth's ecosystem services at $33 trillion per year In 1996, increasing pollution by sewage, pesticides and fertilizers was affecting the freshwater supply in NYC The city invested more than $1 billion to buy land and restore habitat in the region The ecosystem service saved the city $8 billion it would have otherwise spent to build a new water treatment plant and $300 million a year to run the plant

nutrient enrichment

Fertilizers add nitrogen and other nutrients to the agricultural ecosystem Critical load is the amount of added nutrient that can be absorbed by plants without damaging ecosystem integrity Nutrients that exceed the critical load leach into groundwater or run off into aquatic ecosystems Agricultural runoff and sewage lead to phytoplankton blooms in the Atlantic Ocean Decomposition of phytoplankton blooms causes "dead zones" due to low oxygen levels, and lake eutrophication

habitat fragmentation and edge effect

Fragmented habitat creates more edge, which benefits some species such as the cowbird in Midwestern North America Cowbird is a brood parasite

restoration ecology

Given enough time, biological communities can recover from many types of disturbances through ecological succession Restoration ecology seeks to initiate or speed up the recovery of degraded ecosystems Two key strategies are bioremediation and augmentation of ecosystem processes

global change

Global change includes alterations in climate, atmospheric chemistry, and broad ecological systems Acid precipitation contains sulfuric acid and nitric acid from the burning of wood and fossil fuels Air pollution from one region can result in acid precipitation downwind Industrial pollution in the midwestern United States caused acid rain in eastern Canada in the 1960s Environmental regulations have helped to decrease acid precipitation Sulfur dioxide emissions in the United States decreased 40% between 1993 and 2008

climate change solutions

Global warming can be slowed by reducing energy needs and converting to renewable sources of energy Reduced deforestation would also decrease greenhouse gas emissions Stabilizing CO2 emissions will require an international effort International negotiations have yet to reach a consensus on a global strategy to reduce greenhouse gas emissions The Paris climate conference in 2015 aimed to limit global warming to < 2 degrees C compared to pre-industrial levels

conservation biology

Human activities are threatening Earth's biodiversity Conservation biology, which seeks to preserve life, integrates several fields Ecology Physiology Molecular biology Genetics Evolutionary biology It involves the practical application of scientific knowledge to solve problems

loss of ecosystem diversity

Human activity is reducing ecosystem diversity, the variety of ecosystems in the biosphere More than 50% of wetlands in the contiguous United States have been drained and converted to other ecosystems (CA has lost >90% of its wetlands)

habitat loss

Human alteration of habitat is the greatest threat to biodiversity throughout the biosphere In almost all cases, habitat fragmentation and destruction lead to loss of biodiversity For example In Wisconsin, prairie occupies <0.1% of its original area About 70% of coral reefs have been damaged by human activities (warm water causes coral bleaching)

4 factors of chemical cycling

In studying cycling of water, carbon, nitrogen, and phosphorus, ecologists focus on four factors Each chemical's biological importance Forms in which each chemical is available or used by organisms Major reservoirs for each chemical Key processes driving movement of each chemical through its cycle

effective population size

A meaningful estimate of MVP requires determining the effective population size, which is based on the population's breeding potential

3 levels of biodiversity

Biodiversity has three main components Genetic diversity comprises genetic variation within a population and between populations Species diversity is the variety of species in an ecosystem or throughout the biosphere Ecosystem diversity is the variety of ecosystems in the biosphere

the water cycle

Water is essential to all organisms Liquid water is the primary physical phase in which water is used The oceans contain 97% of the biosphere's water; 2% is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwater Water moves by the processes of evaporation, transpiration, precipitation, and movement through surface and groundwater

introduced species

Introduced species are those that humans move from native locations to new geographic regions Without their native predators, parasites, and pathogens, introduced species may spread rapidly Introduced species are a worldwide problem, contributing to ~40% of extinctions recorded since 1750. In 1890 European Starlings were released in Central Park because the group wanted to introduce every bird mentioned in Shakespeare plays into North America Current North America population exceeds 100 million, displacing many native songbirds They roost in hordes of thousands, up to 1 million, damaging crops, carrying diseases, even colliding with planes. Shortly after WWII, the brown tree snake was accidentally introduced from South Pacific to Guam (ship cargo) 12 species of birds and 6 species of lizards have become extinct (having been eaten by brown tree snake) In 1988, zebra mussels were introduced into the Great Lakes They form dense colonies, threaten native species, and even clogged water intake structure causing billions of dollars in damage

depletion of atmospheric ozone

Life on Earth is protected from damaging effects of UV radiation by a protective layer of ozone molecules in the atmosphere Satellite studies suggest that the ozone layer has been gradually thinning since the mid-1970s Ozone depletion causes DNA damage in plants and poorer phytoplankton growth Destruction of atmospheric ozone results mainly from chlorofluorocarbons (CFCs) produced by human activity

Minimum viable population (MVP)

Minimum viable population (MVP) is the minimum population size at which a species can survive

threats to biodiversity

Most species loss can be traced to four major threats Habitat loss Introduced species Overharvesting Global change

nature reserves

Nature reserves are biodiversity islands in a sea of habitat degraded by human activity 7% of world's land in reserves

the nitrogen cycle

Nitrogen is a component of amino acids, proteins, and nucleic acids The main reservoir of nitrogen is the atmosphere (N2), though this nitrogen must be converted to NH4+ or NO3- for uptake by plants, via nitrogen fixation by bacteria Organic nitrogen is decomposed to NH4+ by ammonification, and NH4+ is decomposed to NO3- by nitrification Denitrification converts NO3- back to N2

biogeochemical cycles

Nutrient cycles in ecosystems involve biotic and abiotic components and are often called biogeochemical cycles. Gaseous carbon, oxygen, sulfur, and nitrogen occur in the atmosphere and cycle globally Less mobile elements include phosphorus, potassium, and calcium These elements cycle locally in terrestrial systems but more broadly when dissolved in aquatic systems

overharvesting

Overharvesting is human harvesting of wild plants or animals at rates exceeding the ability of populations of those species to rebound Large organisms with low reproductive rates are especially vulnerable to overharvesting Elephant populations declined because of harvesting for ivory Molecular genetics analysis led to improved anti-poaching effort in Zambia. Overfishing has decimated wild fish populations >25% of the world's wild fisheries are currently at risk of overfishing and collapse The North Atlantic bluefin tuna population decreased by 80% in ten years Cardinal fish are hauled out of Indonesian coral reef waters for pet trade

toxins in the environment

Pharmaceutical drugs enter freshwater ecosystems through human sewage and agricultural runoff Estrogen used in birth control pills can cause feminization of males in some species of fish

the phosphorus cycle

Phosphorus is a major constituent of nucleic acids, phospholipids, and ATP Phosphate (PO43) is the most important inorganic form of phosphorus The largest reservoirs are sedimentary rocks of marine origin, the oceans, and organisms Phosphorous cycle is relatively local

population conservation

Population conservation focuses on population size, genetic diversity and critical habitat Biologists focusing on conservation at the population and species levels follow two main approaches The small-population approach The declining-population approach

two main processes of an ecosystem

Regardless of an ecosystem's size, its dynamics involve two main processes: energy flow and chemical cycling Energy flows through ecosystems, while matter cycles within ecosystems

biodiversity

Scientists have named and described 1.8 million species Biologists estimate 10-100 million species exist on Earth The psychedelic rock gecko was only discovered in 2009 Between 200-2010, biologists identified >1000 new species in southern Vietnam alone Tropical forests contain some of the greatest concentrations of species and are being destroyed at an alarming rate Conservation biology aims to protect and manage biodiversity

biodiversity and human welfare

Species diversity brings humans practical benefits Species related to agricultural crops can have important genetic qualities Plant breeders bred virus-resistant commercial rice by crossing it with a wild population (screened 7000 populations) In the United States, 25% of prescriptions contain substances originally derived from plants The rosy periwinkle contains alkaloids that inhibit cancer growth Madagascar is home to 6 species of periwinkle, and one is approaching extinction The loss of species also means loss of unique genes and genetic diversity

sustainable development

Sustainable development is development that meets the needs of people today without limiting the ability of future generations to meet their needs Sustainable development requires connections between life sciences, social sciences, economics, and humanities Costa Rica's conservation of tropical biodiversity involves partnerships between the government, nongovernmental organizations (NGOs), and private citizens Human living conditions (infant mortality, life expectancy, literacy rate) in Costa Rica have improved along with ecological conservation

declining population approach

The declining-population approach Focuses on threatened and endangered populations that show a downward trend, regardless of population size Emphasizes the environmental factors that caused a population to decline Red-cockaded woodpeckers need forests with low undergrowth

zoned reserve

The zoned reserve model recognizes that conservation often involves working in landscapes that are largely human dominated

biodiversity hot spot

A biodiversity hot spot is a relatively small area with a great concentration of endemic species and many endangered and threatened species

threatened species

A threatened species is likely to become endangered in the foreseeable future 12% of birds and 21% of mammals are threatened

buffer zones

A zoned reserve includes relatively undisturbed areas and the modified areas that surround them and that serve as buffer zones

endangered species

An endangered species is "in danger of becoming extinct throughout all or a significant portion of its range"

greenhouse gases and climate change

One pressing problem caused by human activities is the rising level of CO2 and other greenhouse gases in the atmosphere Due to burning of fossil fuels and other human activities, the concentration of atmospheric CO2 has been steadily increasing. CO2, water vapor, and other greenhouse gases reflect infrared radiation back toward Earth; this is the greenhouse effect This effect is important for keeping Earth's surface at a habitable temperature Increasing concentration of atmospheric CO2 is linked to increasing global temperature Northern coniferous forests and tundra show the strongest effects of global warming In 2012 the extent of Arctic sea ice was the smallest on record A warming trend would also affect the geographic distribution of precipitation