Thursday, December 7, 2023

Science omnivore takes on the tough questions

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Professor Rich McDowell has a lot of high-stakes science on his plate. Tim Fulton reports.
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As chief scientist for the Land and Water National Science Challenge Rich McDowell leads about 150 researchers working on the country’s biggest land and freshwater questions.

The land and water challenge is one of 11 research areas the Government is funding to the tune of $680m over 10 years. 

Our Land and Water’s pot for the next six years is about $69m.

The science challenges have generated more than 400 publications across more than 150 projects since the programme started in 2014. 

McDowell’s job, leading a multi-disciplinary team from at least 16 organisations, is delivering land and water research that can be taken onto farms and into New Zealand’s worldwide agricultural markets.

A web page for the land and water portfolio says because of the research the way we use and manage our land and water will be transformed by deriving greater value in global markets, using land and water in innovative and resilient ways and by building collaborative capacity.”

Under McDowell’s watch researchers are working on projects of vital importance for farmers’ ability to farm, like identifying sources of phosphorus and sediment loss from farms or catchments and pinpointing the most suitable land uses on farms and across catchments.

The challenge projects cover anything from microbes to how much overseas consumers are willing to pay for on-farm environmental management. Finance ranges from $50,000 for a contaminant loading study to more than $3m for an investigation of nutrient sources and flows.

Among the projects researchers have determined the load (kg/yr) of water contaminants in big and small streams, including whether excluding livestock from large streams (more than 1m wide and 30cm deep) in flat catchments used for pastoral grazing will substantially decrease contaminants in a catchment.

The work used a decade (1998-2009) of data to calculate catchment load of nitrogen and phosphorus, suspended sediment and E coli at 728 water quality monitoring sites around the country. The data was combined with catchment characteristics such as climate, topography, geology and land cover and stream size to predict loads for all streams and rivers in NZ. 

The data found in catchments dominated by agriculture 77% of the load came from small streams. That suggests fencing larger streams will affect, on average, only 23% of the national contaminant load. The findings suggest more should be done to reduce the amount of contaminants entering small streams. 

McDowell said the research is being used by local and central government to set policy for improving freshwater. Taranaki Regional Council, for example, committed to fencing more streams than those covered by central government’s proposed stock exclusion regulations.

There is also evidence to suggest real progress is being made at a large catchment to regional scale for sustained efforts to reduce contaminant losses, McDowell said.

Citing colleagues’ work in the region, he said a decrease in sediment and phosphorus loads and increase in water clarity was entirely consistent with the predictions in the efficacy of the implementation of farm plans in the Manawatu River catchment.

The Manawatu-Wanganui (Horizons) Regional Council recently said its Sustainable Land Use Initiative has completed 683 farm plans, with 14 million trees planted covering 500,000 hectares and more than 570,000 metres of waterways fenced. 

Overall stream and river sediment loads are expected to decrease and cause a concurrent reduction of the phosphorus load carried by the river.

The Environment Ministry recently reported that at 159 sites dominated by intensively grazed pasture monitored between 1994-2013, 41% are improving and 21% are worsening while for the 304 sites monitored between 2004-2013, 65% are improving.

This improvement in water quality occurred despite an increase in national dairy cow numbers by 26% and the continued expansion of dairying into new areas commonly used for sheep farming. Sheep numbers decreased by 22% over the same period. 

In examining nine potential causes for the decrease in phosphorus losses there is little evidence it was caused by factors such as a decrease in soil Olsen phosphorus concentrations or using less phosphorus fertiliser. 

However, probable causes are that on-farm strategies are stopping phosphorus loss from land and that together with policy, the actions are being directed to areas on-farm or in the catchment where phosphorus losses are most concentrated. They are called critical source areas and farm environment plans are a way to find and manage them.

McDowell has a particular interest in the practical communication of this sort of research, asking the hard questions.

“I’ve heard people say ‘if we put the right mitigation in the right space we can optimise our property’ but what happens if they do that and the existing operations still do not meet the domestic or international aspirations of water quality or indeed profitability?

At an agricultural science conference at Lincoln last October McDowell argued NZ farming might need iterative design to match production to the most suitable land use and to help farmers meet community aspirations for water quality. 

That moves beyond farm environment plans and the isolation of critical source areas to examine a potential system re-set by considering land use suitability. The suitability concept provides indicators on what a parcel of land can produce, the potential of the land parcels to lose contaminants and the effect of the contaminants on water according to a water quality objective.

“We can no longer massage or force our land to our land uses. We must put the right land use to what the land can suitably do with it.” A land-use suitability study in the Rangitikei River catchment showed what is possible, he said.

Quoting work done by Massey University, he said if there is a move to intensify more than 83,000ha of the catchment, the nitrate loss from the root zone would increase by 55%. 

But because the leached-nitrogen flowed through aquifers where a lot of denitrification occurred most of the leached-nitrogen was converted to gaseous forms and lost to air. The result was that the load in the river would have likely decreased by 6%.

A key to implementing land-use suitability and other novel research is a strong working relationship between farmers and scientists, McDowell said.

Researchers will get best results by asking farmers what work matters to them then gathering the data on farms so farmers see the value in what scientists are doing and, therefore, can extend it among their networks much more efficiently.

Agriculture-oriented scientists should have no pretenses about their ability to promote their work without farmers’ help, he said. 

“I’d be the first person to say that I may not be the right person to stand up at a farmer field day and say that our results apply everywhere without considering how they apply locally. I may not have either the relevance or the mana to do so.”

McDowell is well placed to comment. Something of a scientific omnivore, he’s equally at home in farm science, soil science and freshwater studies. 

Born in Southland, he studied at Lincoln University and went on to win a Benefactor’s Scholarship to Cambridge, one of only six the British university awards annually worldwide.

McDowell then joined the United States Agriculture Research Service before coming home in 2001 and carving out his varied career. He has three masters: his employer Lincoln University, AgResearch as administrative host for the land and water challenge and the government-appointed Science Board running the wider National Science Challenges programme.

The Ministry of Business, Innovation and Employment recently completed its mid-way review of the 11 National Science Challenges.

The Science Board agreed to fund all challenges at the maximum funding amount set by Cabinet in 2013 for July 2019 1 – June 30 2024. Funding for the challenges has been allocated for 10 years in two five-year periods, the first of which is until June 30 2019.

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