Deer impacts on water quality: finding the facts
Deer impacts on water quality: finding the facts
The deer industry is in the first year of a five-year survey of water quality in creeks and streams on high and hill country deer farms. It is thought to be the first time a New Zealand drystock farming sector has tried to put a number on its impact on waterways at a detailed farm level.
“The project should help regional councils and the sector understand the impact of deer farming on the environment,” says project leader Dr Jane Chrystal, an AgResearch scientist.
The research team is trying to build a picture of the impact of deer on different types of high and hill country streams. Some streams begin in the undeveloped tops and finish up in more intensively farmed blocks. By monitoring water quality the length of the stream the team can measure where nutrients increase or decrease along its course.
Chrystal, a farm systems and environmental researcher at AgResearch Invermay, Otago, says deer wallowing creates unique challenges, as it is associated with phosphorous and sediment losses into waterways.
“All waterways have base levels of nitrogen and phosphorous that occur naturally. So when we monitor a farm stream, we need to ask of the nutrients we measure, ‘how much do deer contribute’?”
To answer that, AgResearch and farm-owners are monitoring three properties in the South Island and two in North Island this year, with five more farms to be introduced next year. Chrystal and her colleagues will trek into catchments on these farms every six months. During these visits they will gather water samples along the course of each monitored stream.
They will also assess stream bank condition using a monitoring and rating system developed by AgResearch for the project. From the condition of the stream bank, the researchers expect to be able to predict a site’s potential to add contaminants to the waterway.
Chrystal says that by sampling water at its source in the high country they can determine the ‘base’ or background nutrient levels, before the water is influenced by farming.
“These streams are on the big high-country blocks where farmers might put hinds out for fawning, not intensively-stocked, high density areas. We’re talking matagouri and scrub, canyons. These aren’t lovely streams that people are swimming in.”
It’s a case study experiment where repeated monitoring of a number of catchments over time will be used to build up a database of how water quality is influenced by deer farm management.
For their part, participating farmers have been asked to keep records detailing when stock are moved in and out of paddocks and the number and class of stock involved. Fertiliser records are also needed.
The farmers are also taking water samples from the bottom of the catchment every month and send these to Invermay. All the samples – those collected by both the technicians and farmers – will be tested for suspended sediments, phosphorus and nitrogen, as well as for E. coli as an indication of faecal contamination.
Chrystal says it’s too soon to comment on the results to date because a picture of the actual quality of the water will not be known until a number of samples have been taken over time. Individual spot samples are of limited value for this.
She says while other sectors have different waterway issues, like dairy has with nitrogen leaching, it would be useful to have a broad picture of NZ agriculture. She hopes the sheep and beef sector will soon have funding to follow the deer industry’s lead.
“Different species have different impacts on the environment so we need to find solutions for the impacts that are deer-specific. But then again, many deer farms run sheep and beef so it would be helpful to know what impact they have as well,” Chrystal says.
The waterway work is a Hitting Targets research project, a long-term multi-disciplinary investment by DEEResearch, a joint venture AgResearch and Deer Industry New Zealand (DINZ) that aims to lift the productivity of deer farms.
DINZ environmental stewardship manager Lindsay Fung says he hopes the findings will link on-farm deer management practices with water quality.
“This will enable us to advise farmers and regional councils on the best practices and policies for reducing the impact of deer on the environment. At the moment we have good anecdotal information about what works best, but we need to support this with some hard data,” he says.
The AgResearch team hasn’t yet identified the five additional farms for the 2019 monitoring and would welcome farmers putting their names forward. They need to be able to take a monthly sample and get that on a courier to an AgResearch lab within 24 hours. Anyone interested should contact firstname.lastname@example.org
High and hill country deer farm catchment study leader Jane Chrystal at AgResearch’s Invermay deer farm
Photo credit – Tim Fulton
Scientists head into the South Island back country to take water samples from a deer farm stream
Photo credit – AgResearch