Agricultural eutrophication:

Notes from the upper edge

of the nutrient spectrum

John A. Downing

Iowa State University

Ecology, Evolution, & Organismal Biology

and

Agricultural & Biosystems Engineering

This is where I work (state of Iowa)

IOWA =

50%-99%

Agriculture

(average=

92% row-

crop)

Kansas v Iowa

Present v Future?

Larger, row-crop

farms have greater

debt

Corn production

A little prespective on the world

of intensive cropping you may

be entering…..

Dr. Rick Cruse, Director, Iowa Water

Center (IPR, 14 April 2011)

1” of annual soil erosion form farm land might

be sustainable if you have 36” of topsoil

If you have only 6”, it’s not.

1850’s 1990’s N

(GIS by Kelly Arbuckle, ISU Limnology Lab) Iowa’s landscape has changed.

History of North American

agricultural landscapes

Maize

yield

(world data after Downing 1997, Biogeochemistry)

Nutrients

(X30=ppb)

(X12

=p

pb

)

(30 ppb) (300 ppb)

(1200 ppb)

(12000 ppb)

“iowa limnology”

..with a little help from my friends

Bob Diaz

Gene Turner

Nancy Rabalais

Jack

Jones

Jim

Baker

Fraction of Mississippi River (MS) input to

Gulf of Mexico

(After Howarth et al. 1997, Biogeochemistry)

11% of Gulf of Mexico N comes from Iowa

(2-3% of the N to the No Atlantic) 8-9% of Gulf of Mexico P comes from Iowa

The sources of eutrophication

(Downing et al. 1999, CAST rept on Hypoxia)

•Sources of nutrients (N&P)

•Run-off and streams

•Subsurface drainage

(groundwater)

•Air (rain, snow, dust)

Contrasting views of agriculture:

hero or scoundrel?

Norman Borlaug on modern production

agriculture1: “Had we tried to produce the food of the year 2000 with the technology of 1960,

we would have had to have much more than double the area under cultivation,

which would have meant cutting down forests, plowing up lands that were

marginal …. So what would have happened to wildlife? “

Jared Diamond on modern production

agriculture2:

“The worst mistake in the history of the human race”

1. National Public Radio, Robert Siegel interview (2004)

2. Discover magazine (1987)

Iowa disturbance data: crops

~145,000 km2 (2X Ireland; 2X New Brunswick; ½ Italy, 1/3 Spain)

92% land area cultivated; most agriculture in US

N fertilizer: 94% maize, soybeans rotated Average = 130 kg/ha

P fertilizer: 72% maize, 7% soybeans Average = 3-65 kg/ha

25% of land has subsurface drainage >50% soils >optimum agronomic P

http://www.nass.usda.gov/ia/crops/rankcrop.txt; Dept. Agricultural & Biosystems Engineering, ISU

Iowa disturbance data: animals

16 million pigs (sow = 200 kg)

3.5 million cows (cow = 700 kg)

250k sheep (ewe = 65 kg)

37 million chickens (11 billion eggs/y) (hen = 1.8 kg)

Manure being spread on land as disposal

(masses from Byerly et al. 1967, Science)

A more common modern scene

Some things I’ve learned from repairing

and monitoring lakes like these….

Lesson 1. Some of the most critical “terrestrial”

and “marine” environments may be watersheds,

lakes, and rivers

60-80% of nutrients come from 5-10% of the watersheds

Watershed plumbing more important than land use

Fixing lake water quality (locally) for “P” also helps fix “N” (globally);

and lakes are very valuable to people – so is the sea

Iowa

Gulf of Mexico

(How it looks to me. From Downing

et al. 1999, CAST rept on Hypoxia)

Nutrient export spatially

localized

(60-80% of N & P can

come from <10% of the

land)

(5 cm rain)

Cell erosion (tons/ha)

(cell-level GIS application of AGNPS model)

P loss (tons/ha)

During 10cm rain

Surface

2m

4m

6m

4m

5m

Sub-bottom profile (Rock Creek Lake)

50% filling since construction (45 y)

Lesson 2. Limnological theory is

not just “theoretical”

A dozen diagnostic-restoration

studies and plans use off-the-shelf

models created by limnologists

Theories from limnologists you may

know:

Dillon, Rigler, Schindler, Jones,

Smith, Bachmann, Reckhow,

Nurnberg, Canfield, Walker, Kirchner,

Brandes, Chowdry, Cheng, Larsen,

Mercier, Ostrofsky, Uttormark,

Chapin, Green, etc.

Theories work and are bringing

improved water quality, recreation,

and economics to society

Lesson 3. Bacteria, sewage, and

manure are everywhere

Pattern-sampling of fecal coliforms in

Clear Lake to find levels and sources

Lesson 4. Nutrients move in

unexpected ways and forms

Rain and dust supply enough nutrient to make a lake

hypereutrophic

Groundwater supplies 2X enough nutrients for

hypereutrophy

Gaseous NHx is abundant and is absorbed by lakes and

rivers

Agriculture

43%

Urban

10%

Rain

31%

Groundwater

7%

Ag

impacted

wetland

(internal)

9%

P budget of Clear Lake

Lesson 5. People are important nutrient

sources, even in agricultural regions

Caffeine in storm drains in “sewered” urban land

Clear Lake run-off: 24 to 780 ng/L caffeine

Sewage dilution: 50- to 1700-fold

Lesson 6. Farm animal populations

should be counted, too!

3 million people live in my state, but….

POOP INDEX (Phosphorus Output Of People)

16 million pigs (4x sewage output of New York City)

3.5 million cows (1x sewage NYC)

250k sheep

37 million chickens (11 billion eggs/y)

POOP equivalent population: ~45 million

POOP equivalent human density = 300/km2

(Jamaica =230; India = 313; Spain = 85; Albany NY=269; Madison WI =305; Madrid = 675; Puerto Rico = 428)

Lesson 7. It isn’t just about farming,

plankton, and nutrients

Carp removed Control

Carp removed Control

Lesson 8. Some of our most valuable

“land” might be “water” Generally, $50k-$100k/ha/y

Hard to know the full value of water, because…

We rarely buy and sell whole lakes (or oceans)

….er, except in Canada

Even if we did, this value only represents a tiny part of small part of economic value of water bodies

Therefore, non-market valuation is important

Non-market valuation shows that limnologists and real humans value the same variables

Real-human values

Secchi transparency: (+) Total P & N: (-) Cyanobacteria biomass: (-) Suspended solids: (-) Lake size: (+) Dominance by non-Cyano phytoplankton: (+)

(several pubs by Kling, Herriges, Downing, Egan & Corrigan)

Summary

Agricultural landscapes and waterscapes are changing drastically with increased “production” Landscapes leak; hydrology accelerates

Landscapes drive biogeochemistry Land use and configuration alter flux

Biogeochemistry influences community interactions Phytoplankton dominance exacerbates nutrient problems

Communities feedback on biogeochemistry Exotic fish removal decreases nutrient transport; stimulates

macrophytes; holds sediments

Viable pathway to remediation underscores local values of water quality

When considering new agricultural initiatives, write lost value of water into the equation

Economists devise tricky ways of

finding value of “non-market goods”

Preserve water quality in a eutrophic lake

Stated preference

Revealed preference

130 lake study of revealed preference

Values determined by Travel cost (how much do they spend to get there)

Opportunity cost (how much income do they forego to go there)

Local economic activity suggests high value

• Clear Lake Iowa

– 80 ppb TP; 55 ppb chlorophyll a

– Secchi transparency 0.3 m;

decreased from ca 3 m in 1900

– Tourists spend >$100 million per

year.

– 2000 ha

– >$50,000 per ha each year

“Value” differs from local spending

“Local economic activity” poor indicator of value A burger bought here would probably have been bought

somewhere else w/o lake

Good indicators of value of non-market goods (e.g., lakes, oceans, etc.) are: revealed preference estimates

stated preference estimates

Called: “willingness to pay” or WTP

In USA, required for federal projects (e.g., dams), damage assessment payments (e.g., Exxon Valdez), prioritization for remediation (e.g., Clean H2O Act, TMDL)

Estimation of willingness to pay

Stated preference (Clear Lake) Find $ value of potential referendum on

lake water quality preservation

Revealed preference (Clear Lake) Comparison of:

Number of times people plan to visit with current water quality, vs.

Number of times they plan to visit degraded water body

(130 lakes) Comparison of: Number of times people visit good water quality lakes vs poor

Which limnological variables correlate with value estimates?

Methods

1

1

2 2

22

exp exp, | ,

! !

1 1 exp 2 ,

2 12 1

io icy y

io io ic icios io ic io ic

i io ic

o o c co c

o o c co c

yf y y x x

y y

d d

1 2

1,2, ; 0,1,2,i iy y

Pr Pr ,1 exp

ln

Pr .

ii i

i i

i ii

i

i

myes T

X

m TX

T

(papers in press in J. Agric. Econ. & another to be submitted to L&O

Methods any day now)

Stated preference (1000 surveys):

much are they willing to pay for

keeping current conditions? “Would you vote yes on a referendum to maintain the

current water quality of Clear Lake and avoid the

deteriorated water quality as described under Plan A? The

proposed project would cost you $X (payable in five [$X/5]

installments over a five-year period).”

The value of “X” was varied so that different respondents

were faced with different project costs.

Visitors

Water clarity objects distinguishable 6 inches to 1

foot under water Algae blooms 10 to 12 per year

Water color bright green to brown

Water odor mild odor, occasionally strong

Bacteria possible short-term swim advisories

Fish low diversity, good walleye

Overall, the current condition of Clear Lake can be summarized in terms of

general water color

Stated preference valuation of

current water quality in Clear Lake

Solution by probit analysis considering

influence of socio economic indicators

Non-resident visitors (454,000 y-1):

$148 over 5y

(95% CI $108-$236)

Residents (60,000):

$461 over 5y

(95% CI $272-$1490)

Revealed preference

(analyzing what people do)

Travel cost (recreational demand) modeling

Measure visitors’ costs to get there (fuel, lost salary, etc.)

Clear Lake: see how this would vary with altered water quality

130 Lakes: see how this covaries with observed water quality

Recreational Demand Modeling

Consumer’s surplus

Recreational Demand Modeling

Consumer’s surplus with changed number

of trips due to future poor water quality

Revealed preference (Clear Lake)

1000 surveys:

“trip behavior” now

“trip behavior” if water quality degraded

Travel cost at ¼ and 1/3 wage-rate

Used integral of bivariate Poisson-lognormal model estimated by maximum likelihood Estimated value in presence of socio-economic

indicators

Average visitors’ trip behavior revealed: Change from average 4.5 trips to 1.3

Value of maintaining current conditions: $148-$168 per person per year

500,000 annual visitors

Revealed preference

(130 lakes) 14,000 surveys:

“trip behavior” to lakes of differing water quality

Estimate partial effects of water quality on value

Travel cost at 1/3 wage-rate

Used mixed logit model to estimate significance and signs of water quality characteristics Estimated value in presence of socio-economic

indicators

Average visitors’ trip behavior revealed: Influences of socio-economic factors

Male (-), age (+, -, +), education (+), family size (-), income (+), fish (0)

Limnological characteristics had strong effects

Revealed preference (consumer’s

surplus) analysis showed that

limnologists DO think like humans Real-human values

Secchi transparency: (+)

Total P & N: (-)

Cyanobacteria biomass: (-)

Suspended solids: (-)

Lake size: (+)

Chlorophyll: (+)

Non-Cyano phytoplankton: (+)

(analogous to partial effects in regression analysis)