Bush Heritage Australia project aims to clear the waters for Great Barrier Reef
Sam Skeat (Mulloon Institute) and Paul Hales (Bush Heritage) discuss plant succession, natural processes of erosion and sedimentation among other ecological dynamics on a spring-fed linear wetland site at Yourka Reserve.
Terrain NRM hosted Mulloon Institute's Sam Skeat and Leon Van Wyk for a workshop and mentoring event at Yourka Reserve, in the Upper Herbert River catchment, FNQ. The 43,500 Ha conservation property is owned and managed by Bush Heritage Australia. The principal motivation was to workshop cost-effective strategies that will reduce Total Suspended Solids (TSS) in waterways from Yourka Reserve and thereby reduce sediment loads affecting water quality in the Great Barrier Reef lagoon.
Landscape rehydration mentoring was therefore targeted by delivering content in the field. Examining the diverse habitats and intact landscape patterns enabled discussion of design factors for addressing areas of active gully erosion. Design factors pertinent to Yourka Reserve included wetland and biodiversity protection, gully rehabilitation, maintenance of access roads/tracks and landscape rehydration strategies. The capacity building of management staff focused on reading landscape hydrology, assessing risks and opportunities for erosion mitigation, and evaluating the likely return on effort across different parts of the property.
Key lessons:
Reading the landscape is the foundational skill to be honed.
Landscape patterns and project scale are fitted together through a design process.
Plant growth and landscape processes are fundamentally important for shaping outcomes.
Management and maintenance regimes can deliver multiple benefits.
Duncan Buckle (Terrain NRM) and Sam discuss strategy alongside a deep and highly active erosion gully, incised through a Eucalyptus platyphylla flat in Yourka Reserve.
Reading the landscape
Useful actions to address problem areas of erosion depend on correctly observing and identifying certain landscape features, including but not limited to hydrology, geomorphology, species abundances and habitat diversity. Information that relates to past, current and future landscape function should be compiled and analysed with care, informing the design process and resource requirements for the project.
Paul and Sam engaged in reading the landscape, following a primary flowline upstream where large quantities of decomposed granite sand are being deposited and transported through a stream network in Yourka Reserve.
Landscape patterns and project scale
Rehabilitating large gullies can be costly and present many risks that must be carefully managed. One strategy to reduce risk is to work on a representative landscape pattern at a small scale first, which can be repeated at larger scales once more experience and confidence has been generated. Hydrological patterns repeat like fractals at various spatial scales, however the forces to be mitigated will increase in a non-linear way. This means increasing the scale of projects will present increasingly serious levels of risk including the triggering of regulatory approval processes that must be navigated with due diligence.
Sam and Paul examine gully erosion along a fire break in Yourka Reserve.
Plant growth and landscape processes
To be considered as successful projects, landscape interventions must be based on understanding and working with changing conditions through time. Landscape processes can be classified as biotic (plant, animal and microbe population dynamics, ecological succession, etc.) or abiotic (geochemistry, tide cycles, seasonality, erosion and deposition of sediments, etc.). Even without human intervention, landscapes are highly complex systems because the living and non-living processes are deeply inter-dependent. Reinforcing processes speed up changes through positive feedback loops and regulating or dampening processes will slow down changes through negative feedback loops. Sooner or later, erosion control structures must be colonised by the self-reinforcing growth of plants to minimize erosion and build landscape function over the long-term.
Gully erosion cutting through a firebreak access road in Yourka Reserve.
Management and maintenance regimes
Project success in erosion control or gully rehabilitation depends on timely and effective maintenance beyond the initial phase of establishing a landscape intervention. Risks from a catastrophic failure can be effectively prevented by good design, however, small structural compromises must be detected and repaired as early as possible to prevent a reinforcing positive feedback loop from undermining the whole intervention. If plants are encouraged to colonise structures early, multiple benefits in habitat and biodiversity enhancement can accrue through the process of ecological succession. Carbon sequestration and water infiltration could also be accelerated by regular maintenance checks while managing the establishment of vegetation.
This workshop was part of Terrain NRM’s Upper Herbert Sediment Reduction Project. It is funded by the partnership between the Australian Government’s Reef Trust and the Great Barrier Reef Foundation.
Images: Leon Van Wyk & Duncan Buckle.