Ecosystems at Risk

Analyse the human impacts affecting the nature and rate of change of two ecosystems at risk.

All ecosystems are placed under levels of stress that must be withstood or overcome in the form of evolution in order to adapt and survive. These attributes determine the resilience and vulnerability of each and every ecosystem. These forms of stress fall under two categories; natural and human induced. In regards to natural stress, the term gradual is used as it happens at a slower rate and lesser magnitude than human induced stress. If this occurs, the natural world can adapt to this small amount of pressure over thousands of years through the process of evolution in order to survive. Human induced stress is linked with catastrophic outcomes as it happens at too fast a rate and too high a magnitude to allow for adaptation, thus causing extinction. Each land formation that is cleared has huge ramifications on the intricate life cycle that has formed within different systems. These interferences in the natural life cycle consequently affect significant climatic conditions such as rainfall, weather patterns, world climate etc on a global scale.

An ecosystem at risk is determined by two major factors - vulnerability and resilience. The vulnerability of an ecosystem refers to the ecosystems ability to adapt to a changing environment and restore full function. These changes are caused by alterations in the relationship between the four biospheres. The resilience of an ecosystem refers to its ability to withstand human and natural induced stresses.

One particular ecosystem fitting to this description is the Great Barrier Reef (GBR). This is currently the largest and most biodiverse ecosystem in the world, spanning across 348 000 square kilometres of Australia’s Northeast coast. Starting from the top of Cape York (10 degrees 41’ S, 145 degrees E) 2300km down to just north of Bundaberg. Billions of coral polyps form the basis of this intricate biodiverse marine ecosystem, relying heavily on complex biophysical interactions resulting in its vulnerability. There a number of factors leading up to stresses placed upon this ecosystem in particular, human induced stresses.

Along the southern coastline of Australia, numerous agricultural processes take place for various industries whether it is farming, cattle grazing, mass industrial production for exported goods or crop fields. The utility of this land has blinded the consequences of its affects on the natural habitat. Deforestation and land clearing have increased sediment runoff into the barrier reef through land and soil erosion. This increase in depository into the water has caused harmful affects on the barrier reefs ecosystem; a species known as the Crown of Thorn Star Fish (COTS) is a subsidiary of the starfish family. This is the only one of its kind that actually feeds off coral. The process involves moving over coral forms and taking the zooxanthellea as its source of energy. There is no defence mechanism in place for the coral and the COTS move from source to source as it consumes its food resource until the eventual death of the coral. In previous years there was a small population of the COTS, allowing for the continual rate of growth for coral similar to that of the numbers consumed by COTS. Due to increased sediment runoff, the bacteria introduced into the water system encouraged the growth of the COTS, resulting in a population explosion. Further more, once this epidemic was identified; reef management bodies ventured out into the reef and cut up all the COTS that were found. However, this specific species has the ability to rejuvenate and replicate its self. All the pieces of COTS grew into new, full sized animals, tripling the original population. As a direct result, thousands of square kilometres of coral were completely annihilated. A resolution was introduced in which divers would inject these animals with a chemical, transforming their internal organs into a liquid state. This moderated the population of COTS, however there are still concerns for the numbers unaccounted for. This outbreak had a huge impact on the resilience of the GBR. Through the destruction of many coral species, the reef’s resilience and biodiversity declined considerably.

The location of the GBR is towards the northern part of Australia, relatively close to the equator. The Hadley and Ferrel cells bring in high-pressure systems, comprising of warm and dry conditions. The coral has adapted to these conditions over time, requiring water temperature in between 22-29 degrees Celsius for optimum growth and survival. In addition, water salinity is vital to this process ensuring there is sufficient sunlight available to the marine inhabitants. Lacking in salinity and correct water temp will cause for the coral to bleach. If the process of photosynthesis is obstructed, the coral rejects the zooxanthellea, loosing its colour (hence bleaching) as well as its food source. If the conditions do not return to their normal state, the damage is irreversible. This extreme danger reflects the vulnerability in relation to slight fluctuations within climatic conditions.

Over recent decades, the world’s population has grown exponentially (currently 6.4 billion and projected at 9 billion by 2020). Expansion of grazing and cultivation has increased dramatically to accommodate for the worlds growing population. Increased demand for fodder, fuel, wood and agricultural land has lead to the stripping of trees and there has been an increase in deforestation, erosion, flooding, and drought. Increased irrigation and fertilizer has resulted in salinity, algal blooms and chemical residues. There have been atmospheric and water pollution issues due to urbanization and industrialization. These industrial processes are no longer ecologically sustainable, causing an imbalance in the Earths atmospheric composition. Inadvertently this imbalance in chemicals has resulted in greater heat confinement within the atmosphere, in a simplistic explanation, resulting in global warming. This has lead to increased water temperature within certain time periods throughout the year, increasing the risk of accelerated coral bleaching. In 2006, there was a prolonged period of concerning high water temperatures and many marine biologists feared for one of the worst coral bleaching episodes since the вЂ?90’s. That year cyclone “Larry” occurred; the magnitude of this transformed the heat energy from the water, bringing the conditions back to a favourable state hence preventing a catastrophic bleaching event.

It is clear that this ecosystem is at a considerable risk, facing human induced stress both advertently and inadvertently - Agricultural processes and land clearing has directly impacted the COTS outbreak

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