Category Archives: Water

327 – Heterogeneity of farmers

Farmers are highly heterogeneous. Even farmers growing the same crops in the same region are highly variable. This is often not well recognised by policy makers, researchers or extension agents.

The variation between farmers occurs on many dimensions. A random sample of farmers will have quite different soils, rainfall, machinery, access to water for irrigation, wealth, access to credit, farm area, social networks, intelligence, education, skills, family size, non-family labour, history of farm management choices, preferences for various outcomes, and so on, and so on. There is variation amongst the farmers themselves (after all, they are human), their farms, and the farming context.

This variation has consequences. For example, it means that different farmers given the same information, the same technology choices, or facing the same government policy, can easily respond quite differently, and they often do.

Discussions about farmers often seem to be based on an assumption that farmers are a fairly uniform group, with similar attitudes, similar costs and similar profits from the same practices. For example, it is common to read discussions of costs and benefits of adopting a new farming practice, as if the costs and the benefits are the same across all farmers. In my view, understanding the heterogeneity of farm economics is just as important as understanding the average.

Understanding the heterogeneity helps you have realistic expectations about how many farmers are likely to respond in particular ways to information, technologies or policies. Or about how the cost of a policy program would vary depending on the target outcomes of the program.

We explore some of these issues in a paper recently published in Agricultural Systems (Van Grieken et al. 2019). It looks at the heterogeneity of 400 sugarcane farmers in an area of the wet tropics in Queensland (the Tully–Murray catchment). These farms are a focus of policy because nutrients and sediment sourced from them are likely to be affecting the Great Barrier Reef. “Within the vicinity of the Tully-Murray flood plume there are 37 coral reefs and 13 seagrass meadows”.

Our findings include the following.

  • Different farmers are likely to respond differently to incentive payments provided by government to encourage uptake of practices that would reduce losses of nutrients and sediment.
  • Specific information about this can help governments target their policy to particular farmers, and result in the program being more cost-effective.
  • As the target level of pollution abatement increases, the cost of achieving that target would not increase linearly. Rather, the cost would increase exponentially, reflecting that a minority of farmers have particularly high costs of abatement. This is actually the result that economists would generally expect (see PD182).

Further reading

Van Grieken, M., Webster, A., Whitten, S., Poggio, M., Roebeling, P., Bohnet, I. and Pannell, D. (2019). Adoption of agricultural management for Great Barrier Reef water quality improvement in heterogeneous farming communities, Agricultural Systems 170, 1-8. Journal web page * IDEAS page

319 – Reducing water pollution from agricultural fertilizers

I gave a talk to the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) on July 16, 2019, exploring ways to reduce water pollution from agricultural fertilizers.

Many methods have been proposed to reduce water pollution from agricultural fertilizers. The list includes use of nitrification inhibitors, land retirement, vegetation buffer strips along waterways, flood-plain restoration, constructed wetlands, bioreactors, cover crops, zero till and getting farmers to reduce their fertilizer application rates.

Last year, while I was at the University of Minnesota for several months, I reviewed the literature on these options and came to the conclusion that the option with the best prospects for success is reducing fertilizer application rates. It’s the only one of these options that is likely to be both effective and cheap.

In my talk, I made the case for agencies who are trying to reduce pollution to focus on reducing fertilizer rates.

In brief, I identified three key reasons why there are untapped opportunities to reduce fertilizer rates.

1. Some farmers apply more fertilizer than is in their own best interests. Surveys in the US suggest that something like 20 to 30% of American farmers could make more profit if they reduced their rates. If it was possible to identify these farmers and convince them of this, it would be a rare win-win for farmers and the environment.

2. Even those farmers who currently apply fertilizer close to the rates that would maximize their profits could cut their rates without sacrificing much profit. Within the region of the economically optimal rate, the relationship between fertilizer rate and profit is remarkably flat. New estimates by Yaun Chai (University of Minnesota) of this relationship for corn after corn in Iowa indicate that farmers could cut their rates by 30% below the profit-maximizing rate and only lose 5% of their profits from that crop. For corn after soybeans, the equivalent opportunity is for a 45% cut!

3. Some farmers believe that applying an extra-high rate of fertilizer provides them with a level of insurance. They think it reduces their risk of getting a low yield. However, the empirical evidence indicates exactly the opposite. When you weigh up the chances of an above-average yield and a below-average yield, higher fertilizer rates are actually more risky than lower rates. In addition, price risk interacts with yield risk to further increase the riskiness of high rates.

I think there is a real opportunity to explore these three factors in more depth and try to come up with policy approaches that could deliver reduced fertilizer usage in a highly cost-effective way. Some of it would just be about effective communication (e.g. the design of “nudges”, as popularised in behavioural economics) while some might require a modest financial commitment from government or industry. One idea is to offer something like a money-back guarantee to those farmers who agree to reduce their rates by a specified amount. If they lose money as a result, they get compensation. Because of the flatness of the fertilizer-profit relationship, the payments required would usually be very small.

I recorded the presentation to OMAFRA, and it’s available here.

Further reading

Pannell, D.J. (2006). Flat-earth economics: The far-reaching consequences of flat payoff functions in economic decision making, Review of Agricultural Economics 28(4), 553-566. Journal web page * Prepublication version here (44K). * IDEAS page

Pannell, D.J. (2017). Economic perspectives on nitrogen in farming systems: managing trade-offs between production, risk and the environment, Soil Research 55, 473-478. Journal web page

306 – Economics of green infrastructure in cities: some essentials

During the recent Conference of the CRC for Water Sensitive Cities in Perth, I was interviewed about some of the essential points that non-economists need to be aware of when thinking about the economics of water-related investments in cities. The video is now available.

My team has been part of the CRC since it started back in 2012. In the interview I talk a bit about the work we’ve already done and what we’re doing now, and then identify my three top tips for non-economists: that benefits from an investment relate to the differences in outcomes with versus without the investment (not before versus after); that the timing of benefits and costs can matter greatly to the economic results; and that you need to account to a range of risks that might cause any particular investment to deliver less than you’d hoped.

These issues are spelt out more in the video (13:50 long), which you can see right here.

Further reading

Pannell, D.J. (2015). Ranking projects for water sensitive cities – a practical guide, CRC for Water Sensitive Cities: here

Web site for our CRC project: here

305 – Feeling virtuous: what’s it worth?

We all like to feel good about ourselves. A product that makes us seem virtuous to others, or even to ourselves, would be worth paying more for than its strictly utilitarian value.

That was one of our hypotheses behind a surprising result in some recent research. We were trying to measure the benefits of installing a rainwater tank on an urban property in Perth. We did this by measuring the premium in house sale prices for houses that already had a rainwater tank installed, compared with similar houses that did not.

The results left us deeply puzzled. First, the price premium was enormous: around $18,000. Now the water in a typical tank, when full, is worth about $3, and a tanks lasts for about 15 years. That means that to use enough tank water to make the $18,000 price premium worth paying, you would you would have to use a full tank of water and refill it from rainfall about twice each day every day for the whole 15 years (assuming a 5% interest rate on your home loan). But that’s way beyond actual levels of rainwater use, and it doesn’t rain that much or that frequently in Perth anyway!

We were left scrambling for explanations for the high price premium. As I started off saying, an obvious one is the feel-good factor from knowing that one is contributing to water conservation. It could be a bit like organic food. Some of the price premium for that could reflect people’s concerns about environmental impacts of agricultural chemicals (as well as perceived health impacts).

Another possible explanation is that people may misjudge how much the water captured in the tanks is worth. Water from the tap really is most extraordinarily cheap, whereas the most common experience of paying for water for most people is bottled water, which is most extraordinarily expensive. So it would be understandable to some extent if people got this wrong. We cannot tell from the house sale data what is in peoples’ minds (e.g. about water cost), only the overall result.

A third explanation could be that our statistical analysis was faulty. If you look at the paper you’ll see that we tied ourselves in knots, testing the robustness of the stats in ways that are far beyond my own statistical skills (thanks co-authors), but we couldn’t make the result go away.

There was one more puzzle we couldn’t solve, as well. The price premium for rain tanks is far above the cost of installing a tank, so why doesn’t everybody with a house to sell invest in a rain tank? In fact only a small minority of houses sold do have them. I guess they aren’t aware of the potential price hike.

On the other hand, we don’t know what would happen to the premium if the proportion of houses with installed tanks was to increase substantially. It is likely that the greater supply of tanks would drive down the price premium to some extent.

Further reading

Zhang, F., Polyakov, M., Fogarty, J. and Pannell, D. (2015). The capitalized value of rainwater tanks in the property market of Perth, Australia, Journal of Hydrology 522, 317-325. Journal web site ♦ IDEAS page (includes link to freely downloadable version of the paper)

298 – Potential value from restoring urban drains

I remember as a child playing in the stormwater drains near my home in suburban Perth. The drains were straight, steep-sided, fenced off (to keep us out) and the banks were bare grass, but the water contained little fish, called gambusia, that we loved to catch, not caring that they were actually feral pests.

These days, there is growing interest in restoring urban drains to something approaching a natural stream, including natural vegetation on the surrounding land. In a study funded by the CRC for Water Sensitive Cities, we set out to measure the benefits from restoring a particular drain in Perth.

gambusiaThe drain in question was Bannister Creek, which is really close to my childhood home and those other drains I played in.

In 1979 the creek was straightened, deepened, and made into a traditional drain. During the 1980s and 1990s, the area was urbanised, leading to loss of the wetland system and riparian vegetation, nutrient-rich runoff from lawns and gardens, runoff from industry, and increased erosion and pollution problems in the catchment. Additionally, during high-rainfall events, the increase in the volume and speed of water surging through the now straightened and steeply-banked Banister Creek main drain had become a public-safety risk.

In response, a volunteer group formed (the Bannister Creek Catchment Group), with the aim of improving the creek/drain, including a project to rehabilitate a section of it to a “living stream”. The aim was that this would provide flood-mitigation, local amenity benefits, improved water quality, and slower flow velocity.

The restoration project, from 2000 to 2002, involved giving the creek a more natural shape, with meanders, riffles, fringing sedges, gentle sloping banks, and thick vegetation on the banks.

The transformation from drain to living stream can be seen in Figure 1, which tracks the evolution of the area through time.

living1

Figure 1. Drain restoration over time.

Figure 2 shows the changes at ground level. They were pretty dramatic.

living2

Figure 2. Before and after drain restoration.

To estimate the impact of these changes we examined changes in house prices in the area. We used a statistical model to separate out the various influences on house prices, so that we could isolate the influence of the drain restoration.

This approach means that we are capturing the benefits to local residents, but not possible benefits to others, and not ecological benefits that local residents are unaware of. We expect that the measured benefits would include aspects of amenity, recreation and environmental values.

The results were really interesting, and somewhat surprising in their magnitudes. We found that the restoration project had an influence on property prices over a distance of about 200 metres from the creek. Given that the restored section of the creek was about 320 metres long, quite a large number of property values were affected.

In the first few years after project commencement, property values in the area actually fell, probably reflecting a negative attitude to the substantial earthworks that were required.

However, by 2007 the impact had become very positive. On average, the sale prices of houses in the area rose eventually by an average of 3.9 to 4.7% due directly to the restoration project. Considering only these benefits, the costs of the project were only about 25 to 50% of the benefits.

Overall, the results were very encouraging about the prospects for this type of project to deliver worthwhile benefits to the community.

Further reading

Polyakov, M., Fogarty, J., Zhang, F., Pandit, R. and Pannell, D. (2016). The value of restoring urban drains to living streams, Water Resources and Economics Journal web site ♦ IDEAS page