The healthy landscape on the right of the fence would retain water and nutrients, whereas the 'leaky' landscape on the left has little cover and will have increased overland flow.
A remote sensing tool for monitoring landscape health
Water for a Healthy Country Flagship scientists have developed a quantitative tool to help rangeland managers easily and thoroughly monitor the health, or ‘leakiness’, of grazed landscapes.
18 September 2008 | Updated 14 October 2011
Monitoring landscape health is important to optimise land management practises for sustainable and productive farming.
However, traditional monitoring methods require considerable time, effort and money. This can lead to limited monitoring with critical points of landscape degradation being missed.
The solution: the Leakiness Index and Calculator
To address this problem, a team of CSIRO scientists have developed the Landscape Leakiness Index and Calculator which use high resolution remote sensing tools to monitor rangeland landscapes at a broader and more thorough scale.
'Our aim was to develop a quantitative tool to remotely monitor the health of arid and semiarid landscapes,' says CSIRO scientist, Mr Gary Bastin.
'This will allow land managers to detect changes in the relative condition or health of a site, or set of sites, over time.'
The method indicates the health of grazed landscapes based on their ‘leakiness’.
Landscape leakiness is the extent to which landscapes have lost their capacity to regulate rainwater and soil nutrients, the vital resources for plant growth and related livestock production.
Healthy, functional, ‘non-leaky’ landscapes maintain a good cover of palatable, perennial and productive (3P) grasses. On the other hand, less functional, ‘leaky’ landscapes have low or patchy cover leading to increased overland flows, in effect ‘leaking’ water and nutrients to nearby waterways.
How does it work
There are three inputs for the tool:
remotely sensed maps of the amount and location of persistent vegetation cover at different times (for example from Landsat images)
a digital elevation model (DEM) that shows the three-dimensional shape of the landscape
the boundary or shape of the analysis area, for example a sub-catchment or paddock.
The Leakiness Calculator, a computer program developed by CSIRO’s Dr Adam Liedloff, calculates the relative leakiness of the analysis region. A high Leakiness Index value indicates a leaky, or unhealthy, landscape.
'A Leakiness Index for the site is calculated from these combined data maps using what we have called progressive flow values,' says Dr Liedloff.
“One of the other benefits about the index is that we can make retrospective analyses of landscapes, so we can look at changes or trends over time.”
CSIRO scientist, Gary Bastin
'Basically, progressive flow values keep a running account of what potentially moves between higher and lower pixels within the map and ultimately out of pixels located at the lowest (spill) points within the analysis area.'
The Leakiness Index has been rigorously validated using ground cover, erosion and PATCHKEY data systematically collected at sites within the Burdekin catchment of north east Queensland, Australia.
PATCHKEY provides a classification framework for relating vegetation patches as measured on the ground to remotely-sensed cover.
Putting the tool into action
Use of the Leakiness Index to monitor changes in landscape health has many applications, such as:
investigating the effectiveness of different grazing management techniques
identifying areas of land which need particular attention (e.g. through wet season spelling)
mapping catchments at larger scale for regional and national reporting of changes in rangeland health.
'One of the other benefits about the index is that, by using the Landsat archive, we can make retrospective analysis of landscapes, so we can look at changes or trends over time,' says Mr Bastin.
Working with the Queensland Department of Primary Industries and Fisheries the team has used the Index to improve methods for monitoring the condition of grazed rangelands in the Burdekin catchment.
The Leakiness Index can be tailored to assist monitoring agencies in other areas. For more information please contact Mr Gary Bastin.
Read more about CSIRO’s work in Farm Management.