***A Disturbance Index Approach for Assessing Water Quality Threats in Eastern Cape York (Spencer et al 2016) - see links at the end of this map journal for further information.

Fire

Fire can be a threat to vegetation, biodiversity and water quality, however it is also an integral part of this landscape and the associated ecosystems (as discussed on the Natural values tab).

Uncontrolled fires can destroy large areas of vegetation before they burn out or it rains, as shown by fire scar mapping* for 2015, 2014 and 2013. These fires can be caused by deliberate burning for purposes such as weed control, pasture management, woodland thickening control, wildfire hazard reduction and pig hunting, together with lightning strikes and careless human activity. Uncontrolled fires can directly impact habitat and biodiversity through loss, and also contribute to erosion and subsequent water quality issues and sedimentation.

Generally, fire removes groundcover and organic matter, which otherwise provides protection from runoff and erosion. Early dry season fires (low intensity) tend to burn smaller areas and less groundcover, whereas late dry season fires (high intensity) burn most of the groundcover and also reduce canopy cover. The impacts of fire on water quality in the Normanby Catchment have not been well documented, however research in northern Australia indicates that late dry season fires result in greater runoff of sediments, compared to early dry season burns.** Highly-erodible sodic soils are particularly vulnerable to the effects of fire.***

Uncontrolled fires can be particularly damaging to ecosystems when non-native species are present, for example high biomass grasses such as grader and gamba grasses.

Main image. Line of fire across the landscape - provided by Andrew Brooks.

Linked image. Grader grass - provided by Robbie Burns ©Queensland Government.

*Based on statewide map of fire scars (burnt area) as captured by all available Landsat imagery over the period January to December. Fire scars are automatically detected and mapped using dense time series of Landsat imagery acquired over the period 2010 – 2016. The method has been found to map over 80% of fire scars captured in Landsat imagery with less than 30% false fire rate. The accuracy of 2013, 2014 and 2015 fire scar mapping has been further improved by manual removal of false fires and addition of missed fires.

**The effect of three fire regimes on stream water quality, water yield and export coefficients in a tropical savanna (northern Australia) (Townsend and Douglas 2000) - see links at the end of this map journal for further information. ***Alluvial Gully Prevention and Rehabilitation Options for Reducing Sediment Loads in the Normanby Catchment and Northern Australia (Shellberg and Brooks 2013) - see links at the end of this map journal for further information.

Feral animals

Feral pigs, cattle and horses have contributed to erosion by actively digging up the ground, and trampling and eating groundcover. The rare and endemic plants are particularly vulnerable to this loss from a biodiversity perspective. This disturbance can also accelerate erosion and subsequent water quality issues and sedimentation. Feral animals like pigs and cattle concentrate their impacts on wetlands and riparian zones.

Wild dogs can impact on cattle production and urban areas, and feral cats are a threat to biodiversity.

Main image. Feral pig - provided by Andrew Brooks.

Introduced plant species

Weeds, or introduced plant species, are a major threat to the biodiversity of the catchment* and include plants such rubber vine, gamba grass, salvinia and sicklepod.

The spread of exotic weeds and loss of native plants is the most widespread form of land degradation in the catchment. Aquatic weeds such as hymenachne and salvinia smother native aquatic plants, alter stream flow and deplete oxygen levels in the water column. Weeds such as rubbervine and sicklepod invade riparian areas and waterway benches, and out-compete native grasses and trees.**

The Cook Shire Local Area Biosecurity Plan includes programs currently underway to control a number of pests including gamba grass, salvinia, calotrope and navua sedges, grader grass, pond apple, hymenachne and rubber vine (together with feral animals). ***

On Springvale Station Nature Refuge alone a total of 61 weeds (exotic plants) have been recorded.**** Nine of the weeds are declared as Category 3 under the Queensland Biosecurity Act 2014.^ When the Queensland Government purchased Springvale Station in 2016, the first sighting in Australia of the orange wingstem daisy was made. This significant discovery by departmental staff and experts enabled the government to identify and eradicate existing plants quickly and a control strategy was established.

Main image. Rubber vine growing along eroded gullies on Springvale Station - provided by Robbie Burns ©Queensland Government.

*Laura-Normanby Catchment Management Strategy (Howley and Stephan 2005) - see links at the end of this map journal for further information.

**Normanby Catchment Water Quality Management Plan (Howley et al 2014) - see links at the end of this map journal for further information.

***Cook Shire Local Area Biosecurity Plan 2017-2021 (Cook Shire Council 2017) - see links at the end of this map journal for further information.

****Weed Survey of Springvale Station (William 2016) – see links at end of map journal for further information.

^must not be distributed (sold, traded, released into the environment or given as a gift without a permit)

Surface and ground water usage

Cropping and horticulture in the Lakeland area on basalt soils relies on capture of overland flow, creek flow, spring water and groundwater extraction for irrigation, with bananas the biggest current consumer of water. Preliminary water balance results for the dry season of 2014 and 2015 indicated that there are limited water resources in the upper Laura River catchment, Lakeland farming area and basalt aquifers; with a water deficit during years with below average precipitation and minimal surplus during average years.

Excessive usage of both ground and surface water (springs/creeks) could impact the integrity of the basalt aquifers and downstream environmental flows, Groundwater dependent ecosystems (GDEs) along spring-fed creek and river reaches, and the sustainability of farming in Lakeland.*

Cropping and horticulture is also impacting water quality downstream of Lakeland, as discussed on the Water quality slide (see Physical features tab).

Groundwater dependent ecosystem in the Lakeland area - provided by Jeff Shellberg.

Main image. Spring Dam along Spring Creek in Lakeland, and banana fields in background - provided by Jeff Shellberg.

Linked images. Banana field and central pivot crop circle at Lakeland; spring fed by groundwater from the basalt aquifer in Lakeland that supports GDEs - both provided by Jeff Shellberg.

*Preliminary Dry-Season Water Balance for the Upper Laura River Catchment and Lakeland Agricultural Region, Cape York Peninsula: Implications for Development and Downstream Impacts (Akram et al 2016) - see links at end of this map journal for further information.