The Current Issues - Climate Change

The greenhouse effect is a natural process that plays a major part in shaping the earth’s climate. It is defined in terms of long-term averages and other statistics of weather conditions, including the frequencies of extreme events. Climate is far
from static. Just as weather patterns change from day to day, the climate changes too, over a range of time frames from years, decades and centuries to millennia, and on the longer time-scales corresponding to the geological history of the earth. These naturally occurring changes, driven by factors both internal and external to the climate system, are intrinsic to climate itself. As the climate changes so do the plants that grow in that climate - they adapt to the change. But not all changes in climate are due to natural processes and not all are slow.. Humans have also exerted an influence.

Through building cities and altering patterns of land use, people have changed climate at the local scale. Through a range of activities since the industrial era of the mid-19th century, such as accelerated use of fossil fuels and broadscale deforestation and land use changes, humans have also contributed to an enhancement of the natural greenhouse effect. This enhanced greenhouse effect results from an increase in the atmospheric concentrations of the so-called greenhouse gases, such as carbon dioxide and methane, and is widely believed to be responsible for the observed increase in global mean temperatures through the 20th century. The use of paved surfaces and removal of plants has interupted the water cycle and created urban heat islands.

The relationship between the enhanced greenhouse effect, interupted water cycles, the urban heat isalnd effect and global climate change is far from simple. Not only do increased concentrations of greenhouse gases affect the atmosphere, but also
the oceans, soil and biosphere. These effects are still not completely understood. Also, complex feedback mechanisms within the climate system can act to amplify greenhouse-induced climate change, or even counteract it.

What is clear is that there is the possibility that in the near future we may live in a country with a very different climate to that of even 25 years ago. For Melbourne future trends could inlcude:
• Increased average and summer temperatures. Potential average annual temperature increases are projected to range from 0.3 to1.0°C in 2020, and 0.6 to 2.5°C in 2050.
• Reduced rainfall with models suggesting annual average precipitation changes of -5 to 0% in 2020, and -13 to +1% in 2050.
• More extreme events with more hot days, more dry days and increased rainfall intensity during storm events.

With this in mind the individual can begin to make small changes to the way in which gardens and houses are designed. With temperatures increasing, rainfall decreasing and extreme events more likely coupled with a growing population we are likly to have much larger water shortages, energy spikes and pressure on natural resources.

The Current Issues - Soil Degredation

Increasingly we are noticing the break down of soil structure in all locations. It seems that this is not limited to new housing estates or intensive agricultural land.

Soil structure is determined by the arrangment of pores and aggregates in the soil. This dictates how easy it is for water and air to flow into and through the soil. The type of aggregates affect the soil's friability, the ease with which soil particles
are detached by raindrops and runoff, and the resistance of the soil to the growth of roots and shoots.

We are seeing a decrease in the amount of organic matter and activity that occurs in soil. Typically the worst effected areas are areas which have been left free of vegetation and water for an extended period of time or areas which have been extensivly cultivated for an extended period of time. Organic matter is critical for maintaining good soil structure as it helps bind the soil together. Each time the soil is cultivated soil microbes attack the freshly exposed organic matter. Much of the organic matter is then lost as carbon dioxide, and soil crumbs (aggregates) lose their stability. Cultivation also pulverises the soil, destroying the continuous fine channels (biopores) created by plant roots and soil dwelling animals. It is
these biopores that allow rapid infiltration of water and air.

A soil with low organic matter readily collapses when wetted reducing infiltration of rain and increasing
runoff. Weakened by the loss of organic matter, soil particles readily break down under raindrop impact and
are more easily carried away by the increased runoff. Erosion rates can be five to ten times higher for poorly
structured soil than for well structured soil.

The Current Issues - Solar Power

The Current Issues - Indigenous Vrs Exotic Plants

The Current Issues - Water