Simulating Potential Palmer Amaranth Distribution Under Current Climate and RCP 8.5 Scenario

Erica Kistner-Thomas and Jerry HatfieldUSDA Midwest Climate Hub

2110 University Blvd

Ames, Iowa 50011

Phone: 515-294-9602, Email: erica.kistnerthomas@usda.gov

What makes Palmer amaranth a Great Invader?

Image from DiTomaso and Healy 2007

•Physiology and Phenologyo Fast growth rate of 2-3 inches per dayo Long growing seasono Deep rooting system o High water use efficiency

•Reproductive Biologyo Wind pollinated dioecious weed = ↑ Genetic Diversityo Adapts quickly to novel agroecosystemso Resistance to multiple classes of herbicides o Prolific seed producer (500,000 per female plant)

Many Modes of Seed Dispersal

• Irrigation

•Wildlife

•Plowing

•Mowing

• Spreading manure

•Movement of contaminated farm equipment

•Grain, seed, or feed contamination

Photo by MN Department of Ag and Conservation Corps

(Sauer 1955)

19571926

1915

2012

2013

2016

North America Invasion History

•Native to NA Sonoran Desert o Northwestern Mexico o Southwestern U.S. (CA, NM, AR,

TX)

• 20th Century Range Expansion• Southeastern States • Cotton

• 21st Century Range Expansion• Midwestern States• Corn and Soybean

(Sauer 1955)

Climate Change and Palmer amaranth Direct impacts

• Geographic Range Expansion (Northward)

• Longer Growing Season

• Enhance weed growth and reproduction

Indirect impacts

• Exacerbate the negative impacts this weed has on warm-season crops

• Enhanced resistance to herbicides under elevated C02 levels

Study Objectives

1) Develop bioclimatic niche model of Palmer amaranth using the known distribution in its native North America range

2) Validate model using independent distribution data from non-range in US, Europe, Africa and South America

3) Examine its potential global distribution under o Current climatic conditions (1981-2010)o Future climate under the RCP 8.5 emission scenario for 2050

Inform current and future management of Palmer amaranth in light of climate change

• Process-oriented modeling

• Describes how a species responds to the environment

• Based on eco-physiological growth modelo Growing Degree Days requirements o Min and Max Temperature & Moisture Thresholds (Stress Indices)

• Gridded Climate Data o Current climate (1981-2010)o RCP 8.5 emission scenario (Business as Usual) for 2050

• Final Product: Ecoclimatic Index (EI) o Overall climatic suitability of a given location for the persistence of the target species o EI is scaled between 0 (unsuitable) and 100 (climatically perfect year round)

Bioclimatic Niche Modeling Using CLIMEX

CLIMEX Parameter Values for Palmer amaranth Index Parameter ValuesTemperature DV0 = Limiting low average weekly temperature 10oC DV1 = Lower optimal average weekly minimum temperature 30oC DV2 = Upper optimal average weekly maximum temperature 35oC DV3 = Limiting high average weekly temperature 43oC Degree-days PDD = Minimum degrees days above 10oC needed for population persistence (DV0) 1100oC days

Moisture SM0 = Lower soil moisture threshold 0.008 SM1 = Lower optimal soil moisture 0.02 SM2 = Upper optimal soil moisture 1 SM3 = Upper soil moisture threshold 1.4Cold Stress TTCS = Cold stress threshold (average minimum weekly temperature) -10oC

TTCS = Rate of cold stress accumulation -0.001 Week-1

Heat Stress TTCS = Heat stress threshold (average maximum weekly temperature) 43oC

TTCS = Rate of heat stress accumulation 0.01 Week-1

Dry Stress SMDS = Dry stress threshold (average weekly minimum soil moisture) 0.008

HDS = Rate of dry stress accumulation -0.001 Week-1

Wet Stress SMDS = Wet stress threshold (average weekly maximum soil moisture) 1.4

HWS = Rate of wet stress accumulation 0.005 Week-1

Hot-Wet Stress TTHW = Hot-Wet temperature threshold (average maximum weekly temperature) 30.5 MTHW = Hot-Wet moisture threshold (average weekly maximum soil moisture) 1.35 PHW= Rate of Hot-Wet stress accumulation 0.007 Week-1

Values without units are dimensionless indices of plant available soil moisture. By definition, water-logging occurs at a soil moisture level of 1.

Kistner and Hatfield 2018 in A&EL

Climate Datasets

•30’ gridded (half degree) climate data comprised of monthly averages of • Daily min and max temperatures (oC)• Daily relative humidity levels• Daily rainfall totals (mm)

•Baseline: Current Climate (1981-2010)

Centered on 1995

•Climate Projections for 2050

•RCP 8.5 Emission Scenario o High emission, business as usualo ↑ 3-5 oF (2 oC) in avg global temperatures by 2050

3rd National Climate Assessment, 2014

Palmer amaranth’s Native Range

Palmer amaranth’s Known Global Distribution

Established Population Transient PopulationKistner and Hatfield 2018 in A&EL

Modeled Global Climatic Suitability for Palmer amaranth under Current Climate

Unsuitable OptimalModeled Ecoclimatic Index

Established Population Transient Population

Palmer amaranth detection in South Africa,

Cotton field in North Cape Provinceon Feb 9, 2018

Kistner and Hatfield 2018 in A&EL

Current Climate (1981-2010)

• Key row crop growing regions in Sub-Sahara Africa, South America, and Australia are at risk Kistner and Hatfield 2018 in A&EL

RCP 8.5 for 2050 (CNRM-CM5)

• Range expansion into Canada and northern Europe becomes possible by 2050Kistner and Hatfield 2018 in A&EL

Modeled Climatic Suitability for Palmer amaranth in North AmericaCurrent Climate (1981-2010)

• Potential for further range expansion and infill (MN, ND, and MT)

Kistner and Hatfield 2018 in A&EL

First ND (McIntosh County) detection in summer of 2018

Modeled Climatic Suitability for Palmer amaranth in North America

RCP 8.5 for 2050 (CNRM-CM5)

• Suitability range increases by 21.22% in US and by over 10 fold in Canada by 2050

Kistner and Hatfield 2018 in A&EL

Future Directions• CLIMEX assumes only climate affects a species distribution

• Run simulations incorporating landscape data o Soil properties o Susceptible crop distribution data

• Impact of enhanced CO2 levels on weed growth and reproduction

Conclusions

• Sub-Sahara Africa and Australia are at risk for Palmer amaranth invasion/spread

• Northward range expansion likely by 2050 (RCP 8.5 Emission Scenario)

• Climate change benefits the heat tolerant Palmer amaranth

• Multiple weed management tactics are warranted in light of a changing climate

ACKNOWLEDGEMENTS

•USDA-ARS National Laboratory for Agriculture and the Environment (NLAE): Tom Sauer

•Midwest Climate Hub: Dennis Todey, Charlene Felkley

•CSIRO: Darren Kriticos (Climate Data)

EI = GIA

x SI x SX,

where GIA

is the Annual Growth Index,

SI is the combined Annual Stress, and

SX is the product of interaction terms involving each stress.

ECOCLIMATIC INDEX (EI)