Kerry Jones, Sean Fleischfresser and Rodney Jones, Kabi Kabi Traditional owners on the Maroochy River - Jock Mackenzie, MangroveWatch
How Times Change The use of remote sensing and Indigenous knowledge to understand mangrove change on the Maroochy River, QLD, Australia Bunya Bunya Country Aboriginal Corporation with the Sustainability Research Centre, University of the Sunshine Coast
“ There are cultural sites scattered all over this river.” Arnold Jones
Aerial photograph of the Maroochy River looking south east from Bli Bli - Matthew Brown
Introduction Mangrove forests support a variety of ecosystem functions and services imperative for ecosystem health. Despite the importance of mangroves, mangrove forests worldwide are under threat from human development and climate change. To date, most research on mangrove extent in Australia has drawn on approximately 40 years of remotely sensed imagery, a fraction of the time period required to assess long-term spatial change. This research examined changes in mangrove extent over time, drivers of change, and implications for ecosystem services on the Maroochy River, Sunshine Coast, Queensland, Australia. The research uses historic and current remotely sensed satellite imagery and Kabi Kabi Traditional Knowledge of the Maroochy River to generate a more detailed, holistic and longer time scale of changes in mangrove distribution and extent. The research was conducted by Matthew Brown, Dr. Tristan Pearce, Dr. Javier Leon, and Rachele Wilson from the from the University of the Sunshine Coast together with with representatives of Bunya Bunya Country Aboriginal Corporation (BBCAC), a family owned Indigenous Land Management organisation operating on the Sunshine Coast and comprising of Kabi Kabi, Australian South-Sea Islander and historically connected aboriginal members.
Matthew Brown
Dr. Tristan Pearce
Dr. Javier Leon
Rachele Wilson 1
Figure 1: Location map of the Maroochy River showing the extent of the study area as defined with Kabi Kabi Traditional Owners (purple polygon) and 500 stratified random sample points used for the calibration and validation of classified images 2
Methods 1. Remote sensing Landsat satellite images spanning 1983 – 2016 and containing less than 15% cloud cover were acquired from the USGS Global Visualisation Viewer archive (http://glovis.usgs.gov/). Factors such as salinity and elevation are known to limit mangrove distribution. As such, A Digital Elevation Model (DEM) was applied to establish upper elevation limits for mangroves across the study area. Field data were collected and combined with very-high resolution (0.2m) aerial imagery from Nearmap and multispectral imagery (0.5m) from QuickBird to calibrate and validate land cover. NDVI and NDWI spectral indices were coupled to identify healthy mangrove vegetation and observe long term changes in vegetation health and distribution. The remotely sensed data were classified using an Artificial Neural Network (ANN). 500 points were assigned to the study area using a stratified random sampling approach and manually classified as “mangrove” or “non-mangrove” based on field data and higher spatial resolution dataset including Nearmap and QuickBird imagery. Classified points were then randomly divided into calibration (n=200) and validation (n=300) points. The NDVI, NDWI, DEM datasets were used as inputs for the ANN classifier. The final classification output from the ANN was validated based on an error matrix and the overall, producer, and user accuracies were calculated.
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Traditional Owners describe changes in mangroves on the Maroochy River during a participatory mapping workshop 4
2. Participatory mapping Participatory mapping was conducted ‘on country’ with members of BBCAC to document Indigenous knowledge of mangrove change within the lower Maroochy River. The mapping exercise was conducted as a focus group guided by three key questions: (1) how has mangrove extent changed with time? (2) what are the drivers of change? and (3) has the change in mangrove extent influenced ecosystem services? A scale map of the lower Maroochy River was used to spatially document Traditional Ecological Knowledge and enabled digitisation of the data.
Participatory mapping workshop with Kabi Kabi Traditional Owners at Muller Park, Bli Bli
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Findings 1. Total mangrove area declined by 510 HA (16.6 per year) since 1994 Estimations of 1994 spatial data subject to accuracy show that mangroves occupied 1383 ha. By 1995 however, mangrove cover was estimated at 1342 ha, a 3% decline over the period of 12 months. From 1995 to 1998 total coverage increased by 2.7% before declining again from 1998-2001 by 2%. Data indicated a significant loss of mangrove extent from 2001-2007, experiencing an estimated loss of 48%, or approximately 9.8% per year. This decline is spatially represented, whereby changes from mangrove to non-mangrove features are represented in orange. The largest concentration of habitat loss has occurred at Bli Bli, Marcoola and to the west of Coolum Creek.
FROM LEFT TO RIGHT: Figure 2: Maroochy Waterwatch water sampling sites Figure 3: BBCAC participant’s knowledge of mangrove distribution and extent preEuropean colonisation Figure 4: Changes in mangroves within the lower Maroochy River system between 1995 and 2015 from analysis of satellite imagery 6
Foot bridge on northern Coolum Creek - Matthew Brown
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2. S ubstantial changes in mangrove extent have occurred in the Maroochy River system in the past 150 years Mangrove forest distributions were more widespread within the study area, prior to European colonisation in the late 1800’s, spanning from the mouth of the river in the south to Coolum Creek in the north. Kabi Kabi Traditional Owners described how their ancestors would meet among the mangroves to gather food such as fish and crabs, and collect raw materials from the mangrove trees themselves. Sizeable stands of mangroves were also noted to have occupied the riverbanks to the west of Coolum Creek. This information suggests that mangrove stands stretched at least 17km upstream of the river mouth.
“ More sediment enters the river after rain now...it is taking longer for the river to clear up again” Kerry Jones
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Mangrove forest - Matthew Brown
Aerial photograph of cane fields and the water park along the lower Maroochy River Matthew Brown 9
3. Drivers of change There are four key factors driving changes in mangrove extent in the study area: farming, pollution and sewage discharge, urbanisation, and heightened boating activities.
3.1 Farming European colonisation in the Maroochy River during the mid to late 1800s was identified as the largest contributing factor of declining mangrove extent in the region. Kabi Kabi respondents spoke of destruction of Country on a scale never witnessed before. Severe erosion along the riverbank due to land clearing for farming, particularly along the northern portions of the river, has resulted in instability and sedimentation.
3.2 Urbanisation Respondents identified rapid population growth and urbanisation as the primary driver of current mangrove decline. Aside from the direct removal of mangrove habitat, the intensification of urbanised development, permeable surface and artificial drainage systems was considered by all respondents to have drastically altered natural hydrological flow and deposits pollutants directly into the river affecting mangrove health and water quality. Golf courses throughout the Maroochy region were identified as key drivers of change in mangrove extent due to the overwhelming concentrations of pollution and nutrient runoff exerted during rainfall events.
3.3 Pollution and sewage discharge Local sewage treatment plants were identified as drivers of change in mangroves and river health including; Maroochydore, Nambour, Coolum and Suncoast facilities that evidently discharge treated waste water directly into the waterway. Intense rainfall events and higher than average tides were also said to place additional stress on the treatment plants, often causing system overflows that release raw, untreated sewage directly into the river. This is said to have become a regular occurrence, particularly in recent years where substantial leaks occurred in 2008 and 2012. With the onset of more intense rainfall and rising average sea-levels due to a warming climate, many respondents held the view 10
that the treatment plants and contamination from sewage leaks will continue to degrade mangrove and river health into the future.
3.4 Boating activities Intensified use of the river for recreational purposes was identified as a key stressor influencing change. The increasing number of boats and jet skis used in the river is causing severe erosion of the riverbanks, particularly along areas where mangrove vegetation is already sparse.
Estimates
Drivers
Impacts
Quotes
Late 1800s 2016
Farming
• • • •
Habitat loss Nutrient runoff Erosion Degraded water quality
“A lot of the land was cleared for catle gralizng before the can was there (about 130 years ago)” (Participant 1)
Late 1800s 2016
Urbanisation
• P ollutant and sediment runoff • Removal of cultural sites • Degradations of mangrove and saltmarsh • Urban sprawl • Over fishing • Increased erosion • Introduction of invasive weeds
“At this rate there might be no mangroves left in 50 years” (Participant 3) “More sediment enters the river after rain now... it takeds longer for the river to clear up again” (Participant 2)
1999, 2008, 2012
Pollution and sewage
• Fish kills • Noxious weed growth • Degraded mangrove quality • Chemical leaching
“It let go one night... that killed everything” (Participant 1)
Late 1800s 2016
Recreational boating
• S tructural damage to river bank • Increased pollution/ nutrient loads • Over fishing
“Everybody washes their boats and jet skis on the boat ramp. Even though one or two occurrences won’t have much of an affect, an increase in these activities does” (Participant 2)
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Recommendations 1. I nclusion of local and Indigenous knowledge in decision making Where local and/or Indigenous knowledge of an ecosystem exists, it should be included in studies of ecosystem health and change. Indigenous knowledge is accumulated over time and is passed down from one generation to another and therefore often covers longer time periods than most instrumental measurements used in western science. Indigenous knowledge is a dynamic form of knowledge that considers the environment as a complex, interconnected system whereas western science often reduces the environment to individual parts. 12
“Documenting and integrating Indigenous knowledge with science allows us to transcend common spatiotemporal barriers, opening possibilities of scientific observation beyond previous capabilities and answer questions otherwise forgotten by time.� Matthew Brown
Maroochy River with Mount Coolum in the background - Matthew Brown
The inclusion of Indigenous knowledge in this study generated new insights into changes in mangrove distribution and extent on the Maroochy River that go beyond the capabilities of western science and are relevant to how mangroves and the broader Maroochy river system are managed.
2. Legislation Legislation to protect mangroves needs to be extended to protect areas of historic mangrove cover to allow for mangrove forest restoration and recovery.
3. Health benchmarks Current ecosystem management efforts would be more effective if ecosystem health benchmarks reflected the health of an uncompromised ecosystem. 13
Acknowledgements We acknowledge the Kabi Kabi peoples, and their Elders both past and present, who are the Traditional Owners and custodians of the Country on which this research was conducted. We thank the members and friends of Bunya Bunya Country Aboriginal Corporation for generously contributing to this research, the respondents who shared their knowledge and advice throughout the duration of this project. We would particularly like to thank Kerry Jones, Sean Fleischfresser, Rodney Jones, Arnold Jones and Genevieve Jones for their intellectual contributions. The research was funded by the University of the Sunshine Coast Faculty of Science, Health, Education and Engineering and Dr. Tristan Pearce’s USC Vice Chancellor Research Award. Thank you Nearmap for the images used in this research and the Digital Globe Foundation for supplying QuickBird satellite imagery.
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