Why we need to rehydrate our landscapes
Triple Ponds, Mulloon Creek in 2006 (left) and in 2013 (right).
Landscape rehydration is a key priority in agricultural areas around Australia, with approximately 60% of Australia’s valuable agricultural land degraded and continuing to degrade. These dehydrated landscapes have been negatively affected by soil erosion, compaction, loss of organic matter and the draining of wetlands.
Continuing degradation of floodplains, slope erosion and land clearing has affected the resilience of our catchments to respond to these challenges with devastating consequences, including reduced:
biodiversity
water and soil quality and quantity
productivity of agricultural landscapes
natural fertility
resistance to weed invasion
resilience of landscapes during climatic changes
drought resilience and increased susceptibility to bushfires.
Prior to European settlement
In the Mulloon catchment east of Canberra, the introduction of European farming in the 1820s (and with it a suite of new plant and animal species) resulted in a disruption to the delicate, energy-dissipating balance that had existed between vegetation and the water cycle.
As Johnston and Brierley (2006)* contend, the stream throughout much of the lower Mulloon catchment was discontinuous prior to European settlement, with water moving slowly through a chain of ponds, surrounded by grassy floodplains. When these ponds flooded, water spread across the floodplain, depositing sediments and nutrients and banking water in the landscape. The ponds even remained full during times of drought.
Today, much of the Mulloon catchment and its tributaries are deeply incised, which has serious implications for the catchment’s:
water holding and water filtering capacity
biodiversity
ability to sequester carbon (which is significantly higher in hydrated soil)
water table height (and the ability of vegetation to access such water)
agricultural productivity
resilience to extreme events such as droughts, floods and wild fires.
Since European settlement
This decreased resilience to climatic changes and extreme natural events is particularly relevant and alarming amid Australia’s current bushfire crisis and the ever-emerging consequences of climate change. With the severity and frequency of Australian droughts and fires expected to intensify because of climate change, it is vital that landscape rehydration initiatives such as the Mulloon Community Landscape Rehydration Project (MCLRP), which enhance resiliency to fires, droughts and floods, are proactively supported and implemented with urgency.
The MCLRP being implemented by The Mulloon Institute aims to rebuild the Mulloon catchment’s natural landscape function and boost its resilience to climatic extremes for more reliable stream flows, improved ecosystem functioning and enhanced agricultural productivity. The project spans 23,000 ha, 50kms of creeks and tributaries and involves over 20 local landholders.
Installation of leaky weir at Westview Farm as part of the MCLRP.
Landscape rehydration works are also one of the best practical actions communities can undertake to improve water quality in the wake of bushfires. Bushfires have the potential to degrade waterways as runoff can carry sediment and pollutants that affect the aquatic environment, drinking water quality and water-reliant industries such as agriculture. In the Mulloon catchment, wetlands recreated through the MCLRP are playing an important role in filtering runoff from the December 2019 bushfire in nearby Tallaganda National Park as the MCLRP runs into the Shoalhaven River, which feeds into the Sydney water supply.
* Johnston, P. & Brierley, G. (2006) Late Quaternary River Evolution of Floodplain Pockets along Mulloon Creek, New South Wales, Australia, The Holocene, Volume 12, No. 5, pp 661 – 674.
[Article published in the Carwoola Gazette, February-March 2020.]