global environment change Flashcards
Pollution - how to quantify?
Effect of a chemical depends on the volume or concentration in the animal/plant, or in certain sensitive parts of it.
environment:
* Lethal Concentration (LC)50 - concentration of the chemical in the air/water(environment) that will kill 50% of the test animals with a single exposure.
consumed:
* Lethal Dose (LD)50 – the single dose of a chemical that, when fed to a group of test animals or applied dermally, will kill 50% of the animals.
pollution - what type of effects?
- Additive: effects of each may simply be added together to indicate overall effect
- Antagonistic: one pollutant may cancel out or reduce the impact of another
- Synergistic: pollutants combine in such a way that the environmental effects are greater than would be expected additively
pollution - where from?
- Point source (e.g. a sewage outlet)
- Multi-source (e.g. chimney stacks)
- Seeping (e.g. fertiliser runoff)
- Spreading (e.g. volatiles in air-flows)
acute pollution
- Occurs when a large amount of waste matter enters the environment.
- Usually from a point source, after a one-off accidental event.
- Commonly has a toxic affect on biota
- After event ecosystem begins to recover and return to resemble original situation.
Acute Pollution - oil spills
Crude oil is a blend of many chemical compounds:
* aliphatic hydrocarbons (e.g. hexane and octane)
* aromatic hydrocarbons (e.g. benzene and toluene)
* polar compounds (e.g. ethanol)
* sulphur compounds (e.g. benzothiopenes)
biotic effects:
* around 90% of sunlight is intercepted
* division of algal cells is inhibited at oil levels of as low as 0.01ppm
* food chains are modified (directly and indirectly)
Chronic Pollution
characteristics:
* Low-level input into the environment
* Occurs either more or less continuously or as frequent pulses
* Environment is constantly under stress, albeit light stress
* Ecosystem does not have opportunity to recover and often there is cumulative effect
Chronic Pollution - pesticides
- Highly toxic chemical substances deliberately introduced into an ecosystem to kill or reduce population size or growth of particular pests or weeds.
- Saved many human lives: major players in increases in food and other organic products over past 50 years
- Benefits considerable - reduction in impact of weeds and pests, improved harvests, fewer storage losses, control of human, livestock and crop diseases.
types:
Organochlorine: DDT, aldrin, dieldrin and heptachlor
* broad-spectrumtoxins
* remain in the environment for a long time
Chlorophenoxy: herbicides such as 2,4-D
* chemistry resembles that of plant auxins
* broken down in soil in a matter of days
Organophosphates: malathion, parathion and carbamates
* highly toxic to human
* biodegradable and non-persistant, readily broken down
Chronic pollution - Plastics
- Accumulation of plastic products in the environment adversely affecting wildlife, habitat or humans.
- Prominence correlated with plastics being inexpensive and durable.
- Slow to degrade.
- Affects lands, waterways and oceans.
- Marine animals: entanglement, direct ingestion, or through exposure to chemicals causing interruptions in biological functions.
- Humans: disruption of thyroid hormone levels.
- UK: > 5 million tonnes of plastic consumed annually, only 24% recycled.
microplastics:
* Small particles usually < 5 mm in diameter.
* Come from a variety of sources: cosmetics,
clothing and industrial processes.
* Primary microplastics: manufactured, direct result of human material and product use.
* Secondary microplastics: fragments derived from the breakdown of larger plastic debris.
* Both types persist in the environment at high levels, particularly aquatic and marine ecosystems.
* Can be ingested and incorporated into and accumulated in the bodies and tissues of many organisms
Biomagnification
- Bio-magnification - occurs when an element or chemical compound moves from one compartment to another and occurs at a higher concentration in the second.
Concentration Factor (CF)=(concentration of the pollutant in the consumer) / concentration of the pollutant in the diet.
Bio-magnification occurs when CF > 1
What is biodiversity?
many definitions-for eg. : the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems
Genetic diversity-total number of genetic characteristics in the genetic makeup of a species
Genetic variability-tendency of genetic characteristics to vary
How is biodiversity measured?
Species diversity: number of different species (2 components)
* Species richness: count of species
* Species evenness: quantifies how equal the abundances of the species are.
Simpson’s Reciprocal Diversity Index (1/D)
* D = index
* S = total number of species
* p = proportion of total individuals (n/N) in the i species
At what scale is biodiversity measured?
- 1/D for Assemblage A = 10.00
1/D for Assemblage B = 1.20 - 1/DA > 1/DB reflecting the higher degree of evenness
- For a given species richness, 1/D increases with evenness
ecosystem diversity
- Ecosystem (Ecological) Diversity: variation in ecosystems found in region or variation in ecosystems over the whole planet.
- Can take into account the variation in complexity of a biological community, number of trophic levels and other ecological processes.
- Is the largest scale of biodiversity, and within each ecosystem, there is considerable species and genetic diversity.
Total species diversity in a landscape (gamma diversity) is determined by two different things,
the mean species diversity in sites or habitats at a more local scale (alpha diversity) and
the differentiation among those habitats (beta diversity).
Alpha-looks at diversity at local scale, eg. Front lawn
Beta-difference between various local areas eg. Difference between diversity in 2 different parks
Gamma-diversity of a large landscape eg. Cardiff
- Endemism: a term used to describe the usually limited geographical distribution of a taxonomic group, usually at family, genus or species level.
- Areas of high species richness and a high level of endemism are generally areas of high conservation value, and are often referred to as biodiversity hotspots.
direct use value etc.
- Direct use value: derived from direct role of biological resources in consumption and production
- Indirect use value: derives from the many functions biodiversity performs in providing services critical to human well- being
- Non-use value
biodiversity - direct use
food:
Biodiversity provides food for humans in forms that include meat, fruit, nuts and vegetables, and adjuncts to food in the form of food dyes, flavourings and preservatives.
- Plants: 80% of the food supply of the human population is obtained, directly or indirectly, from just 20 kind of plants.
- Animals: More difficult to enumerate - wide range of species consumed but consumption concentrated on small proportion of species
direct use: medicine, ecotourism and (list) other eg.s
biocontrol, industrial materials, sustainability(fish harvest, fuel-wood)
medicine:
* Significant proportion of drugs derived, directly or indirectly from biological sources.
* 119 pure chemical substances extracted from plant species.
* 35% all prescriptions for chemicals based on plant products.
* Only about 5,000, predominantly temperate, species of higher plants thoroughly investigated as potential sources of new drugs.
ecotourism:
* By definition founded on biodiversity.
* 250 million people take part in international ecotourism per annum.
* Revenue - £80 to £250 billion per annum to national incomes.
climate change - recent / natural causes
Climate change: a large-scale, long- term shift in the planet’s weather patterns or average temperatures.
- Earth has had tropical climates and ice ages many times in its 4.5 billion years.
- Since last Ice Age (ended 11,000 years ago), Earth’s climate has been relatively stable (14 °C). In recent years, the average temperature has been increasing.
- El Niño Event
- Volcanic Eruptions
- Greenhouse Effect
- Solar Activity
- e.g. some evidence Little Ice Age (1450 - 1850) coincided with periods of reduced sunspot activity
- Earth’s Orbit - Milankovitch cycles
- Continental Drift
greenhouse gases and CO2 concentrations
- CO2, CH4, H20 and CFCs.
- CO2 is the major contributor to greenhouse effect.
- CO2 less effective absorber than other gases.
- Concern re CH4 – about 25 times as effective.
- Increase of atmospheric carbon dioxide (CO2) since 1000 (from ice cores in the Antarctica).
- Pre-industrial global average concentration of CO2 was 260 - 280 ppm.
- 1990 CO2 level, about 350 ppm; 14 December 2022, about 417 ppm.
- IPCC predict CO2 levels about 600 ppm by 2060.
climate change consequences
- Sea level rise
- Effects on species
- Distribution of species
- Effects on agriculture
- Patterns in disease
- Human migration
sea levels rise
- IPCC predictions:
- average sea level rise of 12cm by 2030
- 50 cm by 2100
- 50% of humanity inhabits the coastal zones around the world. Lowest lying some of the most fertile
low lying lands:
* 0.5 million people live in archipelagos of small islands and coral atolls.
* 0.5m sea level rise in this rise would reduce habitable area and remove 50% of groundwater.
netherlands:
* Over 50% land below present sea level.
* 400km of dykes and coastal dunes provides protection.
* Estimated cost of protection against 1 m sea level rise: £10,000 million.
freshwater:
* Climate change will affect ground water supplies and reserves in many ways
* Demands of increasing population
* Political - many of world’s major sources of water are shared
bangladesh:
* About 30% of land below 2m contour above sea level.
* Estimates of sea-level rise in this area are 1m by 2050 and nearly 2m by 2100.
* 120 million people located in delta region (Ganges and Brahmaputra).
direct effects on plant species: CO2
- Photosynthetic pathways respond in different ways to elevated CO2
- C3 plants generally respond positively to increased CO2 by increasing photosynthesis
- Plants commonly respond to elevated CO2 concentrations by increasing the ratio of carbon to nitrogen (C:N)
- C3 plants benefit from higher CO2 levels, but do acclimate.
- High CO2 causes partial closing of stomata, reducing transpiration and making plants more efficient in water usage.
- Doubling of CO2 levels increases growth in C3 plants by about 40% and in C4 plants by about 20%.
- Nutrient supply may constrain carbon fixation
indirect:
* Leaves of plants in higher CO2 may be thicker, have more starch and more carbon based defences against herbivores.
* Insects that eat plants usually limited by nitrogen supply - may need to consume more, they may develop slower.
distributions of species - insects
Twentieth-century changes in the range of Speckled Wood butterfly (Pararge aegeria) in Great Britain, plotted by presence in Ordnance Survey 10 by 10 km grid squares.
* A coloured grid cell indicates more than one population in:
1915 –1939 (black)
1940 –1969 (red)
1970 –1997 (blue)
- A northward-shifting species, Silver Washed Fritillary, Argynnis paphia, stable at its southern boundary and extending at its northern edge.
- Blue represents the distribution in 1970,
- Green represents the distribution in 1997.
agriculture
- Negative effects of climate change partially compensated by increased productivity due to fertilization effect of elevated CO2. About 5% reduction in global cereal production
- Increase disparity in cereal production between developed and less developed countries - developed increased by 5%, less developed declined by 10%
- Low temperature constrains on crop production will be lifted in many regions - but some crops require cold to initiate germination
- Theoretically: 1°C increase in mean annual temperature will move northern boundaries 150 - 200 km north
- Pole-ward extension of the northern boundaries of most crops
