Great Barrier Reef-wide summary
The 2013 risk assessment found the greatest water quality risks to the Great Barrier Reef were from nitrogen discharge, associated with crown-of-thorns starfish outbreaks and their destructive effects on coral reefs, and fine sediment discharge which drives light reduction for seagrass ecosystems and inshore coral reefs. Pesticide inputs pose a risk to freshwater and some inshore and coastal habitats.
The overall condition of the reef in 2010-2011 declined from moderate to poor. Inshore water quality was poor overall and varied from moderate to poor depending on the region. Inshore seagrass was in very poor condition overall, and its condition has continued to decline since 2006-2007. Inshore coral reefs were in poor condition overall.
On this page:
- Great Barrier Reef snapshot
- Management Practices
Grazing| Sugarcane | Horticulture | Dairy
- Catchment indicators
Groundcover | Nitrogen | Phosphorus | Sediment | Pesticides
- Marine condition
Water quality | Pesticides | Seagrass | Coral
|Proportion of graziers who adopted improved practices between 2009 and 2011. Target: 50 per cent by 2013||Proportion of growers who adopted improved practices between 2009 and 2011. Target: 80 per cent by 2013||Proportion of producers who adopted improved practices between 2009 and 2011. Target: 80 per cent by 2013|
|Late dry season groundcover as at 2010-2011. Target: 50 per cent by 2013.||Reduction in annual average total nitogren load between 2009 and 2011. Target: 50 per cent||Reduction in annual average sediment load between 2009 and 2011. Target: 20 per cent by 2020||Reduction in annual average pesticide load between 2009 and 2011. Target: 50 per cent by 2013|
Target: 50 per cent by 2013.
From 2009 to 2011, 17 per cent of graziers (1453) adopted improved land management practices. The greatest adoption of improved practices was in the Mackay Whitsunday region (36 per cent).
There are 8545 graziers managing 322,891 square kilometres of land across the Great Barrier Reef catchment.
By June 2011, 62 per cent of graziers were using (A or B) management systems that are likely to maintain land in good to very good condition or improve land in lesser condition.
Major sources of adoption of improved practices were:
- Regional Natural Resource Management bodies, through the Reef Rescue program, facilitated management system improvements by providing incentives to 521 grazing businesses.
- Training and targeted extension through the Queensland Government influenced management practice improvements in 129 grazing businesses. In addition, training provided by AgForward is estimated to have contributed to management practice improvements in 173 grazing businesses.
- The Australian Government’s FarmReady program is an important contributor to services in the grazing industry, through subsidising the cost (with a cap) of training provided by registered private consultants and training firms. An estimated 488 graziers adopted improved practices through training directly relevant to Reef Plan objectives with the support of the Australian Government’s FarmReady program.
Target: 80 per cent by 2013.
From 2009 to 2011, 34 per cent of sugarcane growers (1281) adopted improved land management practices. The greatest adoption of improved practices was in the Burnett Mary region (42 per cent).
There are 3777 sugarcane growers managing 4032 square kilometres of land across the Great Barrier Reef catchment.
By June 2011, cutting-edge (A) or best management (B) practice systems were used by 45 per cent of sugarcane growers for nutrients, 28 per cent for herbicides and 20 per cent for soil.
Major sources of adoption were:
- Regional Natural Resource Management bodies, through the Reef Rescue program, directly facilitated management system improvements in 1281 sugarcane growing businesses.
- A total of 767 businesses improved nutrient management systems through training and extension funded by the Reef Rescue program, in combination with the introduction of Queensland Government regulations.
- Herbicide management system improvements are estimated to have taken place in 431 sugarcane growing businesses.
- A total of 575 sugarcane growers improved soil management systems.
Target: 80 per cent by 2013.
From 2009 to 2011, 25 per cent of horticulture producers (242) adopted improved land management practices. The adoption rate varied across regions and ranged from moderate to very good.
There are 970 horticulture producers managing 595 square kilometres of land across the Great Barrier Reef catchment.
By June 2011, cutting-edge (A) or best management (B) systems were used by 52 per cent of horticulture producers for nutrients, 81 per cent for herbicides and 72 per cent for soil.
Target: 80 per cent by 2013. From 2009 to 2011, 33 per cent of dairy producers (102) adopted improved land management practices.
There are 306 dairy producers across the Great Barrier Reef catchment, with the majority in the Burnett Mary and Wet Tropics regions.
Drivers of management practice change included:
- The Australian Government’s Reef Rescue program, facilitated by Terrain Natural Resource Management, Burnett Mary Regional Group and the DBnBR program:
- At least 73 farmers implemented actions arising from soil and nutrient management plans. Of these, 36 farmers also accessed Reef Water Quality Grants to assist with capturing and re-using sediment and effluent, protecting riparian areas and purchasing machinery suited to minimum tillage cropping.
- There is no data available on management system change by the remaining 65 plus dairy farmers who participated in the Reef Rescue program. Therefore, the stated improvements are likely to be conservative estimates.
- The Queensland Government’s Rural Water Use Efficiency program, through the Dairy and Fodder Water for Profit program, assisted an additional 29 producers to implement improved irrigation and water recycling practices.
Target: 50 per cent by 2013.
The 2011 mean groundcover across grazing lands was high (91 per cent), well above the Reef Plan target of 50 per cent mostly due to high rainfall over recent years. This was 13 per cent higher than the 24-year mean of 78 per cent.
All reporting regions had mean groundcover levels well above the target ranging from 90 per cent (Fitzroy) to 95 per cent (Wet Tropics). The area below the 50 per cent target was less than one per cent in 2011 and 5.2 per cent over the 24-year period.
|Region||24-year mean groundcover (%)||2011 mean groundcover (%)||Area with less than 50% groundcover averaged over past 24 years (%)||Area with less than 50% groundcover in 2011 (%)|
|Wet Tropics – Herbert catchment only||88||95||0.9||0.3|
|Total Great Barrier Reef||78||91||5.2||0.3|
Groundcover changes over time
The 2011 mean groundcover across the Great Barrier Reef catchment is the highest of the past 24 years. This has resulted in a very low proportion (0.3 per cent) of the catchment being below 50 per cent groundcover and corresponds with generally above average annual rainfall in the past five years. The years with the lowest groundcover were 1994 to 1996 and 2004. During these years, mean groundcover for the area was less than 70 per cent and the percentage of area with mean groundcover below 50 per cent was in the range of 13 to 16 per cent. These years had low annual rainfall in preceding years.
Regions with generally high average annual rainfall have consistently high levels of groundcover. For example, the Mackay Whitsunday, Wet Tropics and Burnett Mary regions had mean groundcover greater than 70 per cent over the 24-year period. In addition, the area with mean groundcover below 50 per cent for these regions has been below five per cent for the entire monitoring period. In comparison, regions with lower, more variable annual rainfall (e.g. Fitzroy and Burdekin) show greater fluctuations in groundcover. In these regions, mean groundcover falls in drier years and the area which is below 50 per cent groundcover increases.
Although groundcover is very high and well above the target, sediment loads are still affected by gully, midslope and streambank erosion.
There is often a time lag between the end of a wet period and a reduction in groundcover. Conversely, there is almost no time lag following rainfall for groundcover to be restored.
The catchment loads targets are ambitious measures designed to be met in 2013 for nutrients and pesticides and 2020 for sediment. Catchment modelling has been used to estimate the long term annual load reductions due to the adoption of improved management practices. The model is run over a fixed climate period to account for climate variability.
Target: 50 per cent by 2013.
The estimated annual average total nitrogen load leaving catchments reduced by seven per cent (1133 tonnes). The greatest per cent total nitrogen load reduction (13 per cent) was in the Mackay Whitsunday region with 228 tonnes.
- Agricultural fertiliser use is a key source of dissolved inorganic nitrogen and phosphorus. The estimated annual average dissolved inorganic nitrogen load leaving catchments reduced by 13 per cent (644 tonnes).
- The greatest per cent dissolved inorganic nitrogen load reduction (23 per cent) was in the Burnett Mary region with 100 tonnes.
Target: 50 per cent by 2013.
The estimated annual average total phosphorus load leaving catchments reduced by seven percent (237 tonnes). The greatest per cent load reduction was from the Mackay Whitsunday region with 12 per cent (37 tonnes).
Target: 20 per cent by 2020.
The estimated annual average suspended sediment load leaving catchments reduced by six per cent (354,000 tonnes). The greatest per cent load reduction was from the Burdekin region with 10 per cent (257,000 tonnes).
The regions contributing the highest total suspended sediment loads were the two largest catchments which are dominated by grazing - the Burdekin (3,705,000 tonnes per year) and the Fitzroy (1,881,000 tonnes per year).
Target: 50 per cent by 2013.
The estimated annual average pesticide load leaving catchments reduced by 15 per cent (2237 kilograms). The greatest per cent load reductions were from the Mackay Whitsunday and Burnett Mary regions with 31 per cent (763 kilograms) and 17 per cent (267 kilograms), respectively.
Agricultural lands are a key source of pesticide runoff, particularly cane lands.
Inshore water quality declined from moderate to poor overall which reflects freshwater discharge that was more than five times the annual median flow for the reef. The decline in water quality is a departure from the trend for most years since 2005-2006. Concentrations of chlorophyll a and total suspended solids were very poor and moderate overall.
In 2010-2011, remote sensing of water quality showed a clear gradient of declining water quality from offshore areas to inshore areas more frequently exposed to flood waters. The inshore area of all regions had annual mean chlorophyll a concentrations that exceeded the Great Barrier Reef Water Quality Guidelines with some areas approaching close to 100 per cent exceedance (Great Barrier Reef Marine Park Authority 2010).While some exceedance of the guidelines is expected in the wet season, water quality was at its lowest level since monitoring began in 2005. In Cape York and Mackay Whitsunday, water quality was influenced by a high annual mean concentration of total suspended sediment that exceeded the guidelines (Great Barrier Reef Marine Park Authority 2010). The relatively high concentrations of total suspended sediment in most areas of Mackay Whitsunday may be a result of elevated river discharge since 2007 and continued re-suspension of finer sediment particles by wind and wave action. Regions where the guidelines (Great Barrier Reef Marine Park Authority 2010) were exceeded had water quality scores that ranged from moderate to poor.
Herbicides were detected at all sites in 2010-2011 with high variability between regions and seasons. High photosystem II inhibiting (PSII) herbicide equivalent concentrations generally coincided with periods of high flow from the major rivers in the wet season. Biologically relevant concentrations of PSII herbicides (Category 4) were present at most sites in the Wet Tropics, Burdekin, Mackay Whitsundays and Fitzroy regions.
The PSII herbicide equivalent concentration incorporates both the relative potency and relative abundance of individual PSII herbicides compared to a reference PSII herbicide, diuron. The highest PSII herbicide equivalent concentrations detected in 2010-2011 were in the Mackay Whitsunday region in areas with seagrass meadows and inshore coral reefs nearby.
There is evidence of an increasing trend in PSII herbicide equivalent concentrations since monitoring began in 2005, with Category 4 or greater levels detected at the majority of routine monitoring sites in 2010-2011.
Herbicide equivalent concentrations provide a single reporting parameter for PSII herbicides with a similar mode of action; however, they may obscure differences in the abundance of individual herbicides detected in different regions because herbicide equivalent concentrations also consider the potency of each herbicide. The type of pesticides detected in each region is often related to the land management activities in adjacent catchments. The most prevalent herbicide detected across the reef was diuron which dominated the PSII herbicide equivalent index. Atrazine, tebuthiuron and hexazinone were also frequently detected (Kennedy, K. 2012) and tebuthiuron was the only PSII herbicide that exceeded the Great Barrier Reef Water Quality Guidelines at a routine monitoring site at North Keppel Island in the Fitzroy region.
Samples collected in flood plumes had levels of tebuthiuron and metolachlor that met or exceeded the Great Barrier Reef Water Quality Guidelines and the ANZECC and ARMCANZ Interim Working Level for marine waters, respectively, at multiple sites in the Burdekin and the Fitzroy regions. A range of other pesticides were present including the insecticide imidacloprid which was detected in flood waters in the Fitzroy and Wet Tropics regions.
The overall condition of inshore seagrass meadows in 2010-2011 declined from poor to very poor and has been declining since 2006-2007. Seagrass abundance and reproductive effort were very poor, while nutrient status was poor. However, there are differences between habitats and regions over time (refer to regional sections).
In 2010-2011, the abundance of intertidal seagrasses declined to very poor at most locations from Cairns to the southern reef. However, abundance was moderate at some sites in the northern Wet Tropics and Fitzroy regions. The impact of the flooding reversed any signs of recovery in abundance noted in 2009-2010. The regions of greatest concern for seagrass are the Burdekin, Mackay Whitsunday and Burnett Mary where a decline in abundance was accompanied by very poor reproductive effort, which may result in reduced capacity of local meadows to recover from environmental disturbances.
Seagrass abundance differed according to habitat type. The greatest fluctuations occurred in estuarine habitats, most often in response to prevailing climatic conditions but also with localised weather events such as pulses of nutrient-rich, sediment-laden flood waters and cyclonic activity. Seagrass abundance in coastal habitats has been relatively stable over the past decade; however, there are signs of a continual decline since 2009. Abundance at inshore reef habitats appears to have been in a constant state of decline since monitoring began in 2005-2006. Increases in the nutrient content of seagrass tissue across all habitats reflected local declines in water quality. Further information on seagrass abundance is presented in the regional sections.
Inshore coral reefs declined to poor condition overall in 2010-2011 and the level of cover from competing macroalgae was good. The density of hard coral juveniles and the rate of change in coral cover were poor overall. However, there are differences between regions over time (refer to regional sections).
Results for the cover of hard corals, macroalgae and density of hard coral juveniles are shown in the relevant regional section.
Coral cover declined in all regions to the lowest point since surveys began in 2005 due to a combination of impacts associated with tropical cyclones and broad-scale flooding. In all regions, the incidence of coral disease increased proportionally with the discharge of local rivers. The associated increase in turbidity and the proportion of fine-grained sediments is likely to have had a negative impact on coral growth and recruitment by smothering and limiting the amount of available light.
The density of juveniles declined from 2005 to 2011 in all regions except the Fitzroy where densities remained stable. Overall, Cyclone Yasi had a negative impact on juvenile densities with the largest declines on reefs in the Wet Tropics where juvenile density in 2010-2011 was 65 per cent lower on average. In the Burdekin and Mackay Whitsunday regions, declines in juvenile densities co-occurred with high turbidity from above-median river discharge.
The relatively low cover of hard coral coupled with a decline in the density of juvenile colonies may indicate a lack of resilience of coral communities at many inshore reefs. Acute disturbances in combination with periods of elevated stress from poor water quality are driving changes in the composition and condition of inshore coral reefs.
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