Bar-tailed godwits are the world record-holders for nonstop flight — they can travel from Alaska to Australia in little more than 11 days — but their habitat is being threatened by fertiliser pollution from farms and suburbs.
About 20,000 shorebirds migrate from the Northern Hemisphere to Pumicestone Passage in Moreton Bay, which was listed by the Ramsar Convention on Wetlands of International Importance in 1999.
Last year pollutant loads in the Pumicestone Passage significantly increased from low to high.
Run-off from its fast-developing catchment delivered triple the amount of mud and high loads of nitrogen and phosphorus to the shallow estuary, which is rich in mangroves, sandbanks, and islands.
Agriculture is just one of many pressures as south-east Queensland's population booms, but the state's Department of Environment and Science (DES), Department of Agriculture and Fisheries (DAF), horticulture advocacy group Growcom and Australian Pineapples have come together to tackle fertiliser run-off into Pumicestone Passage with bioreactors.
"Unfortunately there has been some data from the Healthy Land and Water report card which suggests that pollutant loads in the Pumicestone Passage are increasing," DES spokesperson Stephanie Cooper said.
"So we're working with partners across South East Queensland to improve water quality.
"Bioreactors are pretty cost efficient and pretty easy to install — you can do it with the tractors and the farm equipment that are on site.
"There's not a lot of maintenance and they actually work quite quickly."
'We've got to do something'
Australian Pineapples chairman Sam Pike is conscious that how he farms his land can impact a wetland habitat so precious that migratory shorebirds fly up to 25,000 kilometres every year to use it.
DES has funded a three-year trial on Mr Pike's Glass House Mountains property to see if the impressive results to stop fertiliser run-off on a nearby farm can be replicated.
Mr Pike has constructed a bioreactor wall by digging a deep trench in his sandy soil and filling it with woodchips to provide a home for nitrogen-munching microbes.
"It's a very simple, easy way of controlling your nitrate — underground nitrate — flowing into the waterways," he said.
"I guess this is the way of the future in agriculture.
"We've got to do something about it — it treats the symptom, not the actual problem itself, but until we can figure out how to control nitrate a bit better and how to apply it, this will help."
DAF senior scientist Stuart Irvine-Brown said the first bioreactor wall in Queensland was installed on June 6, 2017.
"We've now been monitoring it for five years and it's still removing 100 per cent of the nitrogen that's going into it," he said.
"We are curious to know what the longevity of these systems will be, because in Queensland we have much warmer temperatures than where they've been used in New Zealand and in the United States."
Positive trend in sector
Growcom's project manager Tim Wolens said the project reflected widespread environmental advances in agriculture.
"Overall we're seeing a big improvement in the uptake of best management practices across all the catchments and it has been moving in a positive direction," he said.
Dr Irvine-Brown said the woodchip-filled bioreactor trenches worked best when the nitrogen level in run-off was higher.
"They work by creating a home and a food source for naturally occurring bacteria, which … use the nitrate in the water to respire, or breathe, and then they convert that nitrogen pollution in the water into normal nitrogen gas in the air," he said.
"We also have a sort of wet/dry cycle system dependent on the weather that we get, and again this has an effect on the longevity and the efficacy of these bioreactor systems."
