CHANGES IN ECOSYSTEMS Causes of Change Natural events

CHANGES IN ECOSYSTEMS

Causes of Change? • Natural events • Human interventions

Which Part of the Ecosystem is Changed? • Biotic Components • Abiotic Components

Frequency of Change • • Regular and predictable changes Irregular (sporadic) events One-off events: planned or unpredictable Daily (diurnal) changes Yearly (annual) changes Less frequent changes Slow gradual changes

Regular and Predictable Changes

Irregular Events

One-off Events Planned Unpredictable

Daily (Diurnal) Changes in light intensity Yearly (Annual) Changes in climate

Less Frequent Changes

Slow, Gradual Changes • Must be observed over a long period of time • Rises and falls in sea level • Movement of tectonic plates

Global Monitoring of Ecosystems • Satellite Systems: – MODIS (Moderate-resolution Imaging Spectroradiometer): records properties of clouds, land, atmosphere, ocean; produces global images of snow and ice cover – MISR (Multi-angle Imaging Spectro. Radiometer): measures variation in land surface, clouds and particles in the atmosphere – MOPITT (Measurements of Pollution In The Troposhere): records origin, global distribution & concentration of methane & carbon monoxide – CERES (Cloud and Earth’s Radiant Energy System): measures the energy emitted from land, ocean and atmosphere; measures reflection of sunlight by different surfaces. – ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer): measures surface temperatures, composition and topography/elevation

Predicting the Effects of Change • Because ecosystems are so complex, it is difficult to predict short- and long-term effects of change • Natural changes less likely to permanently disrupt an ecosystem • Human activities more damaging

Human Impacts on Ecosystems • • • Introduction of exotic species Over-harvesting Salinity Dams Eutrophication Waste disposal

Introduction of Exotic Species • Not all exotic species are a problem • Some are invasive – spread rapidly in ecosystems & produce damaging effects – Invasive plant species = weeds – Invasive animal species = pests

Problems with Invasive Species • Prey on native species who have no defenses against them • May bring disease – native species have no resistance • Take over resources required by native animals • Change the environment

Controlling Invasive Species • If a species is declared noxious land owners and the government must act to remove members of this species – Physical control measures – Chemical control measures – Biological control measures – Biotechnology

Biological Control Measures • Classical biocontrol –enemies of the weeds/pests introduced • Conservation biocontrol – using naturally occurring enemies • Biopesticides – naturally occurring agents (e. g. bacteria, fungi, worms) used to kill exotic species

Over-harvesting • Over-harvesting – unsustainable use of a biological resource • E. g. catching a specific species of fish until their population declines so much it can’t recover • Prevention of over-harvesting requires knowledge of: – Where, when and at what age a species breeds – Rate of growth – Time required to reach sexual maturity

Salinity • Salinity – a level of salt content in water or soil that damages soil and degrades water quality • Too much salt in water and soil means native plant species and aquatic animal species are at risk of extinction • Salinity also leads to loss of land for crops & threatens drinking water supply

Salinity • There are two types of salinity: – Dryland salinity – salinity resulting from excessive clearing of trees – Irrigation salinity – salinity resulting from excessive irrigation

Dryland Salinity • Salt is stored below the surface of soil • Australia’s natural vegetation consists of trees/shrubs/grasses with deep roots • When it rains, native plants stop some water reaching the ground & also take up water into their roots • This means the water depth remains constant & salt in the soil is undisturbed

Dryland Salinity • When trees are cleared, more water enters the soil, causing water levels to rise • Rising water levels dissolves salt in the soil and allows it to enter streams/rivers • WATERTABLE – upper underground surface in which rocks/soil are constantly submerged with water

Irrigation Salinity Excess irrigation enters soil Watertable rises Causes dissolved salts to enter water Watertable eventually reaches roots of plants – those that are not salt tolerant will die • When irrigation stops, soil dries out & salt is left at surface • •

Dams Thomson Dam • Unregulated rivers: rivers that have no dams – Have seasonal flows • Reduced flow in summer; heavier flow in winter • Regulated rivers: rivers whose natural flow is disrupted by dams – Flow of the river fairly constant

Ecological Impact of Dams • Natural flow of the river is disrupted • Releasing cold water from the bottom of dams can lower water temperatures • Wetlands may rely on periodic flooding • Movements of native migrating fish stop Eildon Dam

Eutrophication • Is the build up of dissolved mineral nutrients in water • E. g. build up of phosphate in a lake due to run off of fertilisers • Causes many other problems

Algal Bloom • Algae cover surface of water • Amount of light entering ecosystem decreases • Seaweed/algae below surface dies • More organic matter in water • Number of decomposers increases • Decomposers use up lots of oxygen • Fish & other animals die, as they are starved of oxygen

Waste Disposal • Waste disposal includes: – Landfill – Incineration – Disposal into waterways and sea (e. g. treated sewage) • Lead to negative ecological impacts: – Release of toxic chemicals into atmosphere – Bioaccumulation

Natural Succession in Ecosystems • Ecosystems change without human intervention • Succession: the natural replacement of one community by another (with different dominant species) over time • Two types of succession – Primary – Secondary

Primary Succession • Different communities become established on land that was not previously colonised • E. g. the colonisation of land lifted up by an earthquake under the sea

Secondary Succession • Different communities become established on land that was already colonised, but has been disturbed • E. g. a ploughed field, drained dam

Succession • Pioneer species: first species to become established in their new habitat – Can survive harsh conditions – Rapid reproduction • Succession ends when a stable community is established – there is no further change in the dominant species • Stable community known as a climax community

Restoring the Balance • Personal • Local Council • State Government • Federal Government

The Biosphere • Biosphere: contains all the ecosystems of planet Earth • Includes – Living part (biota) – all living things – Non-living part • Atmosphere (the air) • Lithosphere (the soil) • Hydrosphere (the water)

The Ozone Layer • Protect Earth from ultraviolet radiation • Chemicals used by humans have contributed to the destruction of the ozone layer • Many negative effects: – Damaging crops – Harming marine life – Causing cancer