Cons Bio Exam 2

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Habitat losses are

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impacts so severe that nearly all species are adversely affected, or time span needed for recovery is extremely long. Habitat loss is harmful not only to a single kind of animal or plant but to entire ecological communities

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Habitat Degradation:

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Impacts that may affect some but not all of the species, but is temporary
- Agriculture- crops, plantations, livestock
- Extractions – mining, fisheries, wood
- Infrastructure development – human settlement, industry, roads, dams
- Pollution – atmospheric, land, water

Front 3

Degradation of Fresh Water Systems

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- Losses resulting from water diversion, dams and wetland losses
- Only 2% of U.S. rivers run unimpeded
- Less than one-third rivers run unregulated world-wide
- Agriculture and land clearing increases sedimentation in lands and streams

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Pollution in Freshwater Ecosystems

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- Hot water used industries discharged into rivers
- Removal of foliage next to a freshwater ecosystem allows more running water to enter its capacity
- Chemicals discharged into the water, notably from industry or pesticides from farmland can affect the freshwater environment considerably

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Degradation of Marine Ecosystems:

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60% world’s population lives 100 km of coast
- Major impacts caused by toxic chemicals, waste and nitrogen enrichment
- Coastal wetlands destroyed through filling, draining, shoreline stabilization
- Mangrove forests grow at the interface of land and sea

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The Black Sea Example

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- Freshwater input from land is higher than the evaporation
- Bottom is covered with a stratum of anoxic salt water with a high methane and hydrogen sulphide content
- Danube, Dniestr and Dniepr rivers carry 85% of the total input of fresh water into that sea
- Danube alone carries the waste water of 80 million people
- After 1970, a very strong modification of the chemical and biological habitat occurred

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The Black Sea Example (Cont.)

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- Phytoplankton production and copepod abundance increased and with them the abundance of plankton-feeding fishes
- Increase in catches from 200 000 tonnes in 1970 to 600 000 tonnes in 1985
- Explosion of carnivore jellyfish (Aurelia aurita and Mnemiopsis leidy) consuming eggs and larvae
- No predators, are a trophic “dead end”
- Mortality generates bacterial activity and a large quantity of anoxic water near the bottom, further decreasing fish

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Major Proximate Causes of Habitat Degradation and Loss

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Agricultural activities
Extraction activities
Development

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Pollution and Habitat Degradation

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Light pollution
Solid wastes and plastics
Chemical pollution
Air pollution and acid rain

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Great Smokies National Park

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- Visibility has decreased by 40% in winter and 80% in summer since 1948
- Annual average visibility is 25 miles compared to 93 miles in natural conditions

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Ozone at Ground Level

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- A colorless gas, upper atmospheric ozone blocks harmful ultraviolet ray
- Ground-level ozone forms when nitrogen oxide pollution from automobiles, power plants, and industries combines in the air with volatile organic compound

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Acid Rain

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Acid deposition primarily results from the transformation of sulphur dioxide (SO2) and nitrogen oxides into dry or moist secondary pollutants such as sulphuric acid (H2SO4), ammonium nitrate (NH4NO3) and nitric acid (HNO3).

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Approaches to habitat conservation

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- Establishment of National Parks
- Purchase of development rights
- Debt-for-nature swaps (essay 6.4)
- Purchasing rights to timber concessions
- Wildlands Project

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Two Components of Habitat Fragmentation

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1) A reduction in the area covered by a habitat type

2) A change in the habitat configuration, with the remaining habitat appropriated into smaller isolated patches

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Habitat Heterogeneity Vs. Fragmentation

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- Fragmentation results in reduction of habitat and species may or may not adjust to this change
- Naturally patchy habitat rich in internal structure, fragmented landscapes simplified
- Natural landscapes have less contrast between patches
- Features such as roads pose specific threats to population viability

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Metapopulations and Patch Dynamics

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- Metapopulations – systems of local populations linked by occasional dispersal
- The theory of metapopulation dynamics suggests that when small populations become isolated, they face a higher probability of local extinction than do large populations
- Patch dynamics incorporates all factors contributing to landscape changes (such patch size or number and function)

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Fragmentation Process

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- Occurs in differing spatial and temporal scales and in different habitat types
- Biogeographic scale – regions once connected by vast expanses of natural habitat now isolated – e.g. Bering Land Bridge or Isthmus of Panama
- Intermediate scale – landscape fragmentation that occurs over decades
- Fine scale – internal fragmentation of pristine habitat by roads, trails, power lines, etc.

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Consequences of Fragmentation

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- Initial exclusion
- Crowding effect
- Insulation and area effects
- Isolation
- Edge effects
- Matrix effects
- Species invasions
- Effects on ecological processes

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Crowding Effect: Ovenbirds in Maine

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Fragmentation affected pairing success
Males without territories did not mate

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The increased frequency and abruptness of edges can increase the loss of species

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- Populations of the brown-headed cowbird, an edge-adapted species, are currently expanding
- Populations of songbird species are declining

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Edge and Corridor Effect

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- Boundaries between ecosystems have their own set of features and assemblages of species
- Human activities can create edges that are more abrupt than those found naturally
- Movement corridors are strips or clumps of quality habitat that connect otherwise isolated habitat patches
- Corridors can promote dispersal and reduce inbreeding in declining populations

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7 Major Effects of Roads:

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1) Mortality from road construction
2) Mortality from vehicle collisions
3) Modification of animal behavior
4) Alteration of the physical environment
5) Alteration of the chemical environment
6) Spread of non-native species
7) Increase use of area by humans

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Options for Persistence in Fragmented Habitats:

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- Species more tolerant of a range of conditions more likely to thrive in a matrix of human use
Species that can maintain viable populations within habitat fragments
- Species that are highly mobile

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Species Vulnerable to Fragmentation (Box 7.2):

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- Wide-ranging species
- Nonvagile species
- Species with specialized requirements
- Large-patch or interior species
- Species with low fecundity or recruitment
- Species vulnerable to human exploitation of persecution

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Recommendations for Fragmented Landscapes

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- Conduct a landscape / seascape analysis
- Evaluate the landscape of interest within a larger context
- Avoid any further fragmentation or isolation of natural areas
- Minimize edge effects around remnant natural areas
- Include small habitat patches in conservation plans
- Include potential landscape matrix
- Identify traditional wildlife migration routes and protect them

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Recommendations for Fragmented Landscapes (cont.)

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- Maintain native vegetation along corridors to minimize edge effects
- Minimize area and continuity of artificially disturbed habitats to reduce potential biological invasions
- Include active management of small fragments of native habitat
- Avoid activities that disrupt aquatic connectivity

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Feral, Exotic, Alien, and Invasive Species

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- Feral: “having returned to an untamed state from domestication”
- Exotic: “from another part of the world; foreign”
- Alien: synonymous with Exotic
- Invasive: “tending to spread”

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Invasive and Exotic Species

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Any species, that is not native to an ecosystem; and whose introduction does or is likely to cause economic or environmental harm or harm to human health

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Problems of Exotic Introductions

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- Displace native species more aggressive and adaptable
Cases
black and Norway rat worldwide
starlings in North America
- Diseases and parasites.

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Vectors of diseases and parasites

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Blackhead Disease (histomoniasis, protozoan)
- infectious disease of wild turkeys spread into the wild turkey from domestic chickens.
Duck Virus Enteritis (DVE) disease of waterfowl
- Herpes - kills many infected
- spread into wild waterfowl from domestic ducks.

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Problems of Exotic Introductions

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- Displace native species, more aggressive and adaptable
- Diseases and parasites
- Interbreed with native species.

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Ecological & management problems

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- Divert resources from management of native wildlife
- Exotics introduced on public lands, the nutria
- Very risky for introduction
- Species broad niches

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Reasons for Exotic Introductions

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- Aesthetics, European starling, English sparrow
- Economics
- Sport hunting/fishing
- Un-intended - accidents?

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Invasive Plants Threaten Ecosystems

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- Rapid reproduction
- Displace native plants
- Alter ecosystem, Hydrology
- Soil nutrient composition
- Hybridize with native species
- Support other non-native, plants, animals and pathogens

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Why do plants become invasive?

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- Establish easily, similar habitats and climates
- Grow and proliferate aggressively
- Produce a large number of offspring
- Disperse over a wide area
- Persist without cultivation

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Hypotheses to explain establishment and spread of invasives:

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- Novelty
- Biotic Resistance Hypothesis
- Disturbance Hypothesis

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Reasons for Exploitation:

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- Consumption (food, medicine, etc.)
- Economics (money)
- Recreational hunting
- Recreational fishing

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Impacts of Exploitation on Non-target Species:

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- Logging and forest flammability
- Hunting and loss of seed dispersal service
- Cascade of ecological events resulting from removal of top predators

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Characteristics of vulnerable target species:

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- Those that occupy shallow waters accessible to fishing gear
- Those that form dense shoals in predictable places
- Those that are most valuable

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Methods for Calculating Sustainable Yield:

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- Surplus production
- Yield per recruit
- Full demography
- Adjustments based on recent results
- Demographic rules of thumb
- Spatial and temporal comparisons

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Surplus production

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- Can estimate MSY if we know how yields have responded to different levels of exploitation effort over time.
- Problem: Treats each year as an independent replicate, without accounting for lags in the ability of populations to respond to mortality

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Yield per recruit

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- Based on “dynamic pool” concept
Dynamic pool refers to models that keep track of separate processes that add to a population
- Models identify the level of exploitation that maximizes yield
- Problem: requires information on age classes and mortality rates that are usually not available

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Full demography

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- Used in species where detailed information on population exists
- Information necessary includes birth rates, juvenile survival, age at maturity, adult survival
- Problem: use is restricted to species where detailed life history parameters exist

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Adjustments based on recent results

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- Quotas are adjusted each year to account for new information available on the species being extracted
- Hunting licenses in North America are calculated based on health of the population

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Spatial and temporal comparisons

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Inferences about sustainability from simple evidence such as densities in areas of differential hunting pressure; interviews with hunters