We are working with Ecotourism and The Great Barrier Reef Marine Park to try and prepare for the effects of Climate Change, currently one of the hottest and highly debated topics. The Ecosystem of the Great Barrier Reef is complex and understanding how such an intricate system will be affected by Climate Change is as much of a challenge as trying to minimize the impact itself. However, we need to try and understand these threats to the Great Barrier Reef so that we can put in measures to mitigate or adapt to the changes
What is Climate Change?
Throughout history the climate of the world has undergone natural changes. We are currently experiencing a period of warming and it is widely accepted that the cause of this warming is a direct result of the increased levels of Carbon Dioxide in the atmosphere caused by mans actions, (these being from Industrial Developments, Deforestation, Agricultural improvements and the increased use of cars/planes etc).
How will Climate Change affect the Great Barrier Reef?
Unfortunately, weather prediction is very difficult. This chaotic environmental system has many variables that interact and impact upon one another. The prediction of Climate Change and its impacts is very ambiguous with many areas of uncertainty. It is only by drawing on a range of scenarios and assessing changes currently underway that scientists have been able to draw some conclusions and these are discussed below.
There are five recognized factors that will determine the vulnerability of the Great Barrier Reef to Climate Change.
Increasing sea temperatures: Coral reefs grow in a narrow range of environmental conditions and are particularly sensitive to changes in sea temperatures. It is expected that the biodiversity currently found on our reefs will be reduced as the more sensitive of species will be impacted upon to a greater degree than the more robust species. Species inhabiting the shallower waters will be affected more so than those species found in deeper waters. These negative impacts on the coral will in turn impact upon the species that rely on the coral for their food, habitat and ultimate survival.
Irradiance – both visible and UV light: Light from the sun is very important for the growth and development of coral reefs. The symbiotic relationship that corals share with Zooxanthellae demands a sufficient level of sunlight for photosynthesis to occur. However, too much irradiance can result in too much stress on the coral; an example of this is coral bleaching, a well-known reaction to increased irradiance. Climate Change may determine levels of irradiance in two ways:
Changing weather patterns will affect cloud cover; in periods of drought there will be prolonged periods of intense sunlight but at the same time the increase in temperature may increase evaporation from the ocean thus creating greater cloud cover.
The frequency of drought breaking floods may increase and with them the runoff of sediment which will reduce visibility and limit the amount of sunlight that penetrates the water.
Ocean Acidification: As we have mentioned one of the causes of our climate changing is increasing levels of CO2 in the atmosphere; furthermore, these increasing levels are making their way in to the oceans. Unfortunately this is having a direct impact on the pH level of the oceans and is causing acidification.
Corals have a core ingredient, limestone, and the lowering pH of the water is going to negatively impact upon the integrity of this limestone. It may be that this change in ocean chemistry will have the largest detrimental effect upon the Great Barrier Reef as far as climate change is concerned. Not only will it affect the integrity of already deposited limestone but it will also impact on the ability of corals to physically produce limestone.
4. Frequency of intense tropical storms: Definitive answers on this factor have been difficult to determine but it is the general consensus that an increase is sea temperatures will increase the intensity of tropical storms. Severe storms will cause bigger waves and a mixing of the water column that will lead to coral breakage and dislodgement, burial of species by sediment and rubble and a removal of algae. Those smaller and more fragile species will be at most risk from breakage. Following a Category 4 or 5 Cyclone a healthy reef will take approximately 20 years to recover, it is not known how a reef under stress from Climate Change will react to such an event.
5. Altered rainfall and river flood plumes: Most reefs grow in waters that are low in nutrients. Climate Change models are making initial depictions that we will suffer longer and more frequent drought periods that are broken with severe floods. Intense rainfall will always deliver runoff and soil nutrients along with fertilizers and pesticides to the ocean and these may be further increased as ground cover is cleared due to fires during periods of drought leaving exposed soils behind. These compounded effects will lead to an increase in nutrients that will promote the growth of algal species.
A further impact of this may be increased outbreaks of the Crown of Thorn Starfish. This species tends to prosper after a flood when the nutrient rich waters aid the growth of phytoplankton. The larvae of the starfish depend on this phytoplankton for food and growth and so the rate of survival for these starfish is much more successful.
Summary: In general we are expected to see a decline in:
Structural complexity and habitat,
Diversity, especially in the more sensitive species.
The deterioration in other reef environments such as the Caribbean indicates that the community will shift from being a coral dominated system to an algal-dominated one. However, the full extent of climate change is not yet fully understood and consequently, we do not have any definitive answers on how the ecosystem will respond to climate change.
What can we do?
As users of the Great Barrier Reef Marine Park we must realise the susceptibility of our operations to the stresses of Climate Change. In association with GBRMPA and EcoTourism Australia we have documented aims and objectives so that we can be prepared for the impacts that Climate Change may have on our operations and the Industry in general. For instance, we are currently trying to measure the Carbon Footprint of the business so that we can offset this.
It is the consensus of many that the issue of Climate Change is such a global challenge that as an individual or group of people we cannot really do much to alleviate the problem. However, trying to reduce our Carbon Emissions is something that we can all try and focus on so that we can take steps to minimize the change in climate that is experienced. This includes not only our direct carbon emissions but also those that result from products that we purchase and services that we use.
The Great Barrier Reef Marine Park Authority is taking steps to educate users of the Marine Park to Climate Change and its threats. GBRMPA is currently working with the Australian Greenhouse Office on a $2 million CC response Program whose aim is to:
“Increase knowledge about the implications of Climate Change for the GBR social and ecological systems and to develop support strategies to minimize impacts through improving and maintaining resilience”
The complexity and diversity that makes the Reef so vulnerable to change is also what gives it its stability and strength to make a full recovery. We must try to minimize our current impact on the Reef so that the Ecosystem is at its strongest to cope with the changes in the climate. Ensuring that our activities and those of our passengers do not leave a detrimental mark on the ecosystem is paramount in helping it to survive.