Silt in flood waters

Dirty waters

Our wet winter has resulted in our rivers running brown and plumes of brown water where they enter the sea along the north-west coast.

Increased siltation of our waterways poses a high risk to the Giant Freshwater Crayfish. Siltation or sedimentation can affect a crayfish’s ability to breathe oxygen through the gills, and this affects the animal’s health, particularly during its juvenile stage.

Sedimentation can come from bed or bank erosion within a waterway, from stock access and in-stream stock watering points, from dirt roads and farm crossings, from exposed soil in or near waterways and from land clearing in the catchment.

Vegetation, especially deep-rooting woody vegetation on the top of the river bank, is essential to hold the banks together and prevent erosion. It is also important to leave a well vegetated buffer zone between the paddock activities and the waterway, to filter out nutrients, soil and fine sediments carried downhill in wet seasonal conditions. Access tracks and farm crossings also need vegetated buffers (which can be grass and not just trees) between their runoff drainage and the waterway, to filter out the sediment and nutrients. Waterway crossings need careful design and installation, avoiding bends in rivers and creeks where water velocities are always higher. Pipes and culverts are easily blocked by sediment and woody debris and can lead to increased bank and bed erosion. Bridges are more expensive to install but often cost less in long term maintenance, whereas gravel crossings or causeways are cheaper to install but may lead to major bed erosion which is difficult and expensive to fix and often leads to loss of productive land when banks are undermined and collapse as a result of bed lowering. Giant Freshwater Crayfish do not cope well with crossings or culverts and often travel overland to avoid them.

Soil erosion from farming and cropping activities can also turn the waterways brown. Reduce the risk through measures such as cover cropping, cultivating on the contour of the slope and maintaining vegetated buffers between production land and waterways.

Local agriculture forum talks productivity and sustainability

On Friday the 6th of August the second WalkerAg Consultancy Industry Forum was held in Ulverstone, bringing together farmers and expert speakers to discuss the latest advances in crop agronomy, natural asset protection and farm education programs.

This forum is becoming recognised as a key event in the north-west agricultural calendar, led by local independent agronomist Tim Walker from WalkerAg Consultancy and supported by the agricultural industry across the region, including the Cradle Coast Authority.

CCA Agriculture Project Coordinator, Ali Dugand, presented at the forum on the use of seasonal cover or ‘breaker’ crops to reduce the risk of soil erosion, and how to incorporate them into a mixed farming rotation.

‘Cover crops cost approximately one-tenth of the value of the soil potentially lost due to erosion and they also have many other benefits for north-west farmers including improving soil structure, water infiltration and nutrient availability’ , said Ali.

Around 90 people congregated to listen to an array of expert speakers, on diverse topics including: Onion variety trials and new disease management options New aspects of biosecurity legislation in Tasmania Slug control options with reduced withholding periods Benefits of foliar nutrient applications for crop yield as well as pest and disease resilience Training and education opportunities for agricultural apprentices

To conclude this learning and networking event, Henry Terry of Tasmanian Truffles delivered a thought-provoking session, giving an insight into the logistics of establishing a truffle orchard. Since the advent of COVID-19, his business has increased their value-adding component to remain competitive in the national and international marketplace – a good message for all producers.

For more details: Ali Dugand Protecting Our Productive Soils Project Coordinator adugand@cradlecoast.com

This project is supported by Cradle Coast Authority with funding from the Australian Government’s National Landcare Program.

IPCC Report - a call to action

The sixth assessment report from the Intergovernmental Panel on Climate Change (IPCC) was released in August. 234 scientists read 14,000+ research papers to write the UN's IPCC report, making it the most comprehensive climate report ever released… and the results are definitive. Humans are responsible for the observed warming of the atmosphere, lands and oceans and urgent action is required to reduce greenhouse gas emissions from fossil fuel burning and deforestation.

The latest IPCC report says that within a decade, global warming could push temperatures to 1.5 degrees Celsius above preindustrial levels, and calls on policymakers to take urgent action on climate change.

So far, the world has warmed by just under 1.1C, the report concludes. That's compared to the "pre-industrial" baseline, which is treated as the average temperature from 1850 to 1900. That might not sound like much, but consider this: when the world exited the last ice age, all it took was 5C of warming. And that happened over 5,000 years.

During that period, it took about 1,000 years to warm by 1.5C; now, we're on track to warm 1.5C in about 50 years.

Humans have not existed in a climate like this before, and it's getting worse. If we reach 2.5C of warming, that will be a temperature the Earth has not sustained for at least 3 million years.

While the IPCC's report makes for grim reading, there are some reassuring details.

It isn't too late to secure a future where warming is kept below 1.5C and we avert many of the most worrying impacts.

In November the world is gathering at the COP26 climate change conference in Glasgow, Scotland. Countries are expected to "ratchet up" their pledges to cut greenhouse gas emissions in line with their promise to try to stop warming at 1.5C.

You can view the Summary for Policy Makers (39 pages) or the full report via this link: https://www.ipcc.ch/report/ar6/wg1/

Flooding is projected to become more common in Tasmania because of climate change. This picture was taken at the Inglis River in 2016 after flooding.