45-1 copyright 2010 mcgraw-hill australia pty ltd powerpoint slides to accompany biology: an...
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45-3 Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Humans in Australia (cont.) Grasslands were turned over to pasture Forests were cleared Cities were built without adequate planning for wastes and effluents Now, ecosystems are under threat by –loss of biodiversity –coastal and urban development –inappropriate land and water use –over-exploitation of resources –spread of exotic speciesTRANSCRIPT
45-1Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Chapter 45: Human impacts
45-2Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Humans in Australia• The Australian biota evolved in an increasingly arid
climate following the break-up of Gondwana• Immigration of other fauna started when continent
approached South-East Asian plate (bats, rodents)• People entered northern Australia at least
40 000 yrs ago• Initial impacts were from fires• European colonisers came in 1500–1600s to
‘conquer and civilise’ the land
45-3Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Humans in Australia (cont.)• Grasslands were turned over to pasture• Forests were cleared• Cities were built without adequate planning for
wastes and effluents• Now, ecosystems are under threat by
– loss of biodiversity– coastal and urban development– inappropriate land and water use– over-exploitation of resources– spread of exotic species
45-4Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Losing biodiversity• It is likely that 20% of all species will become
extinct in the next 30 years• 27 mammals and 1 bird species have become
extinct since European settlement• Seagrass beds are at risk due to water quality • Biodiversity hotspots
– Examples: flora of south-western Australia, north Queensland rainforest, wet sclerophyll forest
• Hot spots may reflect the areas most studied, so relative sampling intensity must be considered
45-5Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Discussion question 1:
Why conserve biodiversity?
Why conserve biodiversity?• Ecosystem services• Bioresources• Aesthetics• Philosophy• Custodial reasons
• About 1.4 million species have been described, total unknown
• Functional classifications may be easier and more ecologically informative than taxonomic ones
45-6Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
45-7Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Tropical forests• Unparalleled diversity of species• Natural disturbances are tree fall and fire• Rapid nutrient cycling enables high production• Low nutrient storage in soil, high in biomass, so
clearing removes nutrients• Slash-and-burn agriculture uses small plots, but is
only productive for a short time• Rainforest regeneration is very slow
– affected by selective weeding and absence of animals for dispersing seeds
45-8Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Land clearance and habitat fragmentationMany land fragments are too small to support viablepopulations. Impacts of fragmentation depend on• Ecology and dispersal ability of organisms• Dependence of species on native vegetation• ‘Stepping stones’• For plants, small refuges may be important
45-9Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Habitat corridors link adjacent fragments• These links effectively increase habitat size• Facilitate movement of animals (and genes)
between patches, so encourage viable population sizes
BUT• They also help spread weeds, pests, diseases,
deleterious genes and fires
• Fragment shape and ratio of edge-to-middle are important factors
45-10Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 45.5a: Habitat fragmentation
Copyright © Byron Lamont, Western Australian Herbarium
45-11Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Introducing new species• Intentional and unintentional introductions have led
to ecological disturbances e.g. Phytophthora cinnamomi fungus (causes dieback disease), rabbits, foxes, feral animals, Japanese sea-star, black-striped mussel, cats
• Strict quarantine controls now apply• Successful invaders have
– high mobility, fecundity and survival– a lack of natural predators– a broad diet– tolerance to a wide range of conditions
45-12Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Integrated pest management• The coordinated use of several control techniques
– Example: rabbits viruses (myxomatosis and rabbit calicivirus) poisoning warren ripping fumigation
• Cane toad– failed to control sugar cane beetles, and became a pest
itself by out-competing native species for food– has toxic skin secretions that kill vertebrate predators– has now reached Kakadu—major ecological disaster
likely
45-13Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. B45.3c: Spread of the cane toad
45-14Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Impact of weeds• A weed is a ‘plant growing in the wrong place’• Usually opportunistic species, e.g. blackberry,
Bitou bush• May grow rapidly and provide cover for foxes,
rabbits• May degrade native animal habitats• Ornamental (garden) species can become weeds
if they spread into native bush, e.g. Pittosporum undulatum
Fig. 45.6: The weed Spartina
45-15Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
45-16Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fresh water is the key to life• A critical resource in Australia• River flows have been altered reduced biodiversity• Flood control death of terrestrial trees (Murray
River)• Water harvesting salinity, temperature, oxygen
changes, pollution• Watering points encourage hard-hoofed animals (that
compact the soil) as well as native grazers that reduce vegetation cover
45-17Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Holding on to soil• Land clearing no surface litter layer or root
mat greatly accelerates top-soil loss • Compaction by hard-hoofed non-native animals
reduces porosity increased water run-off • Reduced vegetation cover increased wind
erosion• Improved farming practices include
– no-till system– leaving stubble after harvest
Fig. 45.9: Wind erosion
45-18Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
45-19Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Discussion question 2:
What would cause soil acidification?
Soil acidification• Repeated application of ammonia-based fertilisers
without liming• Addition of organic acids• Growing legumes • Plant yield drops when pH reaches 5 or less• 12–24 million ha agricultural land is presently at or
below pH 4.8• Improved land management is vital • Acid sulphate soils are common in coastal areas
45-20Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
45-21Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Dryland salinity • Salt is naturally present in soil or groundwater, but
out of reach of plant roots• In wet areas rain washes salt out of soil; in dry
areas soil salinity is higher• Tree removal causes reduced evapotranspiration
(and hence discharge) of ground water, so water table rises
• When less than 2 m from surface it rises further, by capillarity
• Recharge (from rainfall) and discharge zones may be far apart
Need catchment-based management
45-22Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig 45.10: The salinisation process
45-23Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Irrigation salinity• Results from irrigating soils to grow crops• Excess water recharges ground water• Discharge is slow because there are no deep-
rooted trees• Water table rises and brings salt to surface• Signs of salinised soil
– replacement of salt-sensitive species with tolerant ones until no plants can survive
– salt scald occurs and then crust forms – salt drains into streams, into river system and the sea
45-24Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Prevention of dryland salinity• Stop clearing native vegetation• Replant using deep-rooted species, e.g. eucalypts• By 2050, approx 17 million ha in Australia are
predicted to be affected by dryland salinity – south-west WA is worst affected (> 4 million ha)– SA, Victoria and NSW are also affected– ground water levels are still rising in Murray–Darling
basin
45-25Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Polluting the atmosphereEven the Arctic icecap has black soot; global effectsof pollution are the ozone ‘hole’ and global warming
• Ozone (O3) layer is 13–20 km above earth• Shields earth from destructive UV radiation• Constantly created by action of sun on oxygen• Depleted by natural and man-made constituents in
the air, e.g. chlorofluorocarbons (CFCs)• When rate of destruction of ozone > rate of
formation, ‘hole’ forms
45-26Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Effects of UV radiation• Depend on the wavelength: A, B and C• UV-C and -B are the most harmful, but nearly all
filtered out by ozone layer• For each 1% decrease in ozone there is a
2% increase in UVB at earth’s surface• UV radiation reduces uptake of CO2 by
phytoplankton• UV-A causes sunburn and skin cancers• Montreal Protocol target is to get ozone levels
back to normal by mid-21st century
45-27Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Greenhouse effect• Natural warming of earth • Greenhouse gases CO2, N2O, CH4 and water
vapour absorb heat that would be lost to space, raising temp of earth by 30°C
• Post-industrialisation levels of these gases are rapidly increasing, mostly due to fossil-fuel burning
45-28Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 45.14: Mechanism of the greenhouse effect
45-29Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Global warming• Intergovernmental Panel on Climate Change
(IPCC) was established in 1988, and in 2001 concluded that warming over the last 50 years was due to human activities.
• Climate models project global surface temperature will rise 1.4–5.8°C, and sea levels rise 9–88 cm, by 2100
• Rainfall patterns will change in space and time• Changes in ocean currents may occur
45-30Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Coral bleaching• Coral polyps stressed by warm water expel their
symbiotic algae, and die • Bleaching has been reported in reef corals from all
tropical oceans • Coral distribution patterns may change as a result
of global warming
Rising sea levels• Sea levels are expected to rise due to heating and
expansion of seawater• Many low-lying cities are at risk, and some whole
nations, e.g. Nauru
45-31Copyright 2009 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
45-32Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Reduction of emissions• 30% of Australian CO2 emissions are due to fossil
fuel use, agriculture, land clearing and forestry
Discussion question 3:What are the best ways to reduce CO2 emissions?
45-33Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Some ideas for reducing CO2 emissions• More efficient lighting, cars, industry• Change to cleaner fossil fuels (e.g. natural gas)• Adopt non-carbon fuels (solar thermal,
photovoltaic, wind, geothermal, tidal)
45-34Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
45-35Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Towards sustainability• Convention on International Trade in Endangered
Species (CITES): bans trade in listed species• Environmental Protection and Biodiversity
Conservation Act 1999 (Cwlth) conserves ecosystems and their components
• Victorian Flora and Fauna Guarantee Act 1987• Protection of whole habitats is achieved through
Nature Reserves and National Parks• Permits are now required for some activities, e.g.
clearing native vegetation
Fig. 45.17: Exotic wildlife trade
45-36Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
45-37Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Managing natural communities for conservation• Prevention of degradation is needed across a
variety of land tenures, not just reserves• Market-based approaches (i.e. farmers paid to
manage natural areas) are gaining popularity• Traditional use of fire to produce diversity of
habitat patches is being recognised
45-38Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Restoration ecology: resetting the clock• Whole landscapes may need restoring, e.g. wheat
belt in WA• Need data on habitats, species, patterns• Incorporate a suitable disturbance regime to
produce mosaic of habitat patches high diversity
• Replanting methods may include direct seeding of local species
• Soil fungi and bacteria should be incorporated from unmodified systems
45-39Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Ecologically sustainable development (ESD)• A sustainable society ‘all human activity takes
place within the limitations set by the environment’• In 1992 the Australian government adopted a
National Strategy for ESD (NSESD) to safeguard intergenerational equity, with seven main objectives
A global society developed along ESD principles is the only solution
Summary• The impact of humans on the Australian
environment has greatly accelerated over the last 200 years
• More than half of agricultural land in Australia is affected by land degradation
• Human impacts have effects on a global scale• Ecologically sustainable development is required if
the resources on which life depends are to be maintained
45-40Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University