Koalas

Plants absorb nutrients and water through their roots, but photosynthesis - the process by which plants create their fuel - occurs in the leaves. Therefore, plants need to get fluids and nutrients from the ground up through their stems to their parts that are above ground level.

Just as animals, plants also contain vascular tissues (xylem), which transports water and minerals up from the roots to the leaves, and phloem, which transports sugar molecules, amino acids, and hormones both up and down through the plant.

The leaves of plants also contain veins, through which nutrients and hormones travel to reach the cells throughout the leaf. Veins are easy to see some leaves (a maple tree, for instance). In some plants the veins are hard to see, but they're in there.

Sap is the mix of water and minerals that move through the xylem. Carbohydrates move through the phloem. There are several different "modes of transportation" through the xylem and phloem; their main function is to keep all cells of the plant hydrated and nourished.

Inside the cells of the root, there is a higher concentration of minerals than there is in the soil surrounding the plant. This creates root pressure, which forces water up out of the root through the xylem as more water and minerals are "pulled" into the root from the soil. This force results inguttation, which is the formation of tiny droplets on the ends of leaves or grass early in the morning.

The reason the droplets are seen in the morning is because transpiration - the loss of water from leaves - doesn't occur at night, so the pressure builds until morning. Those droplets are not just water, they're sap. And, those sap droplets are proof that water and minerals get pulled up from the soil and transported through the entire plant.

Guttation may work well for small plants, but gravity works against the upward movement through larger plants, so more active processes are involved.

The koala does not transmit any diseases to humans. However, they do spread disease within their own populations. A major threat to the koala populations of Australia is the organism chlamydia, which has four major effects:

• blindness
• pneumonia
• urinary tract infection
• reproductive tract infections, ultimately rendering animals infertile.

Scientists are still working on a cure, as this disease is easily spread, and decimating some of the populations on the mainland.

Koalas do not eat gum trees: they eat gum tree leaves.

Koalas live in eucalyptus trees and eat only a few types of gum leaves from which they get all nutrients and water requirements. They also occasionally eat the gum tree blossoms. Two of the koala's digits on their forelimbs act as opposable thumbs, enabling koalas to reach out and grasp the leaves they want.

While there are hundreds of different eucalyptus species in Australia, koalas eat from only about 60 of the species, consuming about half a kilogram of eucalyptus leaves every day. Koalas select from just 14 species as their primary food source, specifically, the subgenus Symphyomyrphus. Preferred eucalyptus species vary depending on their locality, so that the species eaten by Victoria koalas will be different to those eaten by north Queensland koalas. Koalas have been known to also eat the buds, flowers and bark of these particular species, while dirt also seems to supplement mineral deficiencies. Koalas have been seen feeding in eucalypt trees such as Manna Gum, Swamp Gum, Blue Gum, Forest Red Gum and Grey Gum.

Accurate figures are difficult to determine. The Australia Koala Foundation estimates that koala numbers in the wild have dropped to below 80 000. Research suggests the figure may be as low as 43 000.

As a species, the koala is not endangered in Australia, but some local populations have been reduced considerably.

The conservation status of koalas varies from region to region in Australia. For example, due to farming, land clearing and habitat loss, native koalas were eradicated from Western Australia and South Australia in the last century, but moves have been made to reestablish new colonies in both states. Currently, koalas are thriving on Kangaroo Island in SA, and in other isolated colonies.

Koalas are still listed as "common" in most parts of Queensland, but in the southeast region of Queensland, their status will soon be changed to "vulnerable", following a drop of over 60% in koala numbers in the past decade.

The NSW Government listed the koala as "rare and vulnerable" in 1992, and following protective measures, this has been changed to "vulnerable"; as a result, koala numbers are improving. In Victoria, the koala is not on the threatened species list at all, and in some protected and remote regions, there is actually an overpopulation problem. Where new colonies have been established on Kangaroo island, off the coast of South Australia, there is also beginning to be some concern regarding overpopulation.

Koalas are not officially endangered, and are currently not in danger of extinction. They are at risk from numerous threats, however.

During the late 1800s, koalas became an export commodity for their fur, mostly for export to the USA. Due to koala numbers dwindling and public outrage, laws were enacted protecting the koala and imports were banned by the USA in the late 1920s. By this stage, the koala had been driven to extinction in South Australia.

New colonies have been introduced in South Australia and Western Australia, and within these protected environments, the koala is thriving. Man is their biggest threat, causing loss of food source and habitat loss. Increasing urbanisation results in more koalas being killed by cars, unsupervised dogs, bushfires and even directly by cruel and irresponsible people. In particular, koalas have a range of home trees, and their territory is often split by roads through new urban developments. As a result, when koalas try to wander from one of their home range trees to another, they are hit by cars. Domestic dogs pose another major threat to koalas in suburban fringes.

The conservation status of koalas varies from region to region in Australia, but in no state are they legislated as "endangered". For example, due to farming and land clearing, native koalas were eradicated from Western Australia and South Australia in the last century, but moves have been made to reestablish new colonies in both states. Currently, koalas are thriving on Kangaroo Island in SA, and in other isolated colonies.

Koalas are still listed as "common" in most parts of Queensland, but there are calls to list them as vulnerable in southeast Queensland, where koala numbers have dropped by about 60% in the last decade.

The NSW Government listed the koala as "rare and vulnerable" in 1992, and following protective measures which have seen koala populations regenerate, this has been changed to "vulnerable". The koala is, however, all but gone from the NSW central coast.

In Victoria, the koala is not on the threatened species list at all, and in some protected and remote regions, there is actually an overpopulation problem. They are considered to be "secure" in Victoria.

Despite urging by conservation groups since around 1992, Australia's federal government has refused to list the koala as vulnerable. Even international conservation groups cannot agree. Meanwhile, the International Union for Conservation of Nature (IUCN) lists the koala as "potentially vulnerable", while the US Endangered Species Act lists the koala as "threatened".

Having said that, however, just because the species is not officially threatened does not mean that they are free from threats to their future existence.

The chief threat to the koala is habitat loss. Koalas inhabit prime land which man has decided is better used for housing developments. Not only do the koalas lose their sources of shelter and food, they are subject to dog attacks and being hit by cars as suburbia extends further outwards. A prime example of this is southeast Queensland, where koala numbers have dropped to 60% less than what they were a decade ago, entirely due to increased development - and where they now face extinction by 2020.

Koalas are territorial, and they live in complex social communities where each member has a certain number of trees within its territory. When access to these trees is cut off by new roads, the koalas will still try to cross the road, and risk being hit. Relocation of koalas is rarely successful because their territorial and social habits are largely misunderstood.

Another significant factor is predation by introduced species such as dogs and foxes.

Koalas are also subject to the disease chlamydia, which affects the koalas' fertility, and eventually leads to their death. Currently, there is no cure for this disease. At the best of times, the koala is a slow breeder, usually producing just one joey a year.