Crop pests and pathogens move polewards in a warming world

Is climate change affecting pest distributions? Many studies have shown that wild species’ distributions are shifting poleward due to global warming. Are crop pests and pathogens moving too?

Daniel P. Bebber & Sarah J. Gurr Department of Biosciences, University of Exeter, UK

Methods The latitudes and dates of the earliest record of 612 crop pests and pathogens were abstracted from two exhaustive historical databases: the CABI Distribution Maps of Plant Pests, and of Plant Diseases.

Strong evidence that pests are shifting Observational bias, where developed countries at high latitudes detect pests earlier than developing countries at low latitudes, would result in an apparent shift towards the Equator (as seen in cryptic groups like viruses and nematodes). Despite huge variability among species, observed positive latitudinal trends in many taxa support the hypothesis of global warming-driven pest movement. Introduction through trade is probably the main cause of pest spread, but climate change is allowing establish in hitherto unsuitable regions.

Latitude vs. year of earliest record for all pests, in the Northern and Southern hemispheres. Fitted values (wide line) and standard errors (narrow lines) are derived from Generalized Additive Mixed Models.!

Year

Latit

ude (°)

32

33

34

35

190019201940196019802000

North

−24

−22

−20

−18

190019201940196019802000

South

Mean latitudinal shift (km yr-1) per species for pest taxonomic groups in the Northern hemisphere for all years, and for 1960 onwards. Positive values denote a poleward shift, negative values a shift toward the equator. Error bars show 95% CI.!Aca = Acari, All = all data, Bac = Bacteria, Col = Coleoptera, Dip = Diptera, Fun = Fungi, Hem = Hemiptera, Hym = Hymenoptera, Iso = Isoptera, Lep = Lepidoptera, Oom = Oomycota, Nem = Nematoda, Pro = “protozoa”, Thy = Thysanoptera, Vir = viruses.!

Rate (km y−1)

NemVir

ThyAll

DipOom

IsoBacAca

HymFun

HemColProLep

−40 −20 0 20 40 60

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●

●

●

●

●

●

●

●

●

●

●

●

●

●

All

−40 −20 0 20 40 60

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●

●

●

●

●

●

●

●

●

●

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1960+

Year

Dis

tanc

e fro

m e

quat

or (k

m)

−1000−500

0500

1000All Acari Bacteria Coleoptera Diptera

−1000−500

0500

1000Fungi Hemiptera Hymenoptera Isoptera Lepidoptera

−1000−500

0500

1000

1960 1980 2000

Nematoda

1960 1980 2000

Oomycota

1960 1980 2000

Protozoa

1960 1980 2000

Thysanoptera

1960 1980 2000

Viruses

Latitude versus year of observation for pest taxonomic groups in the Northern hemisphere from 1960 onwards. Fits for all pests combined are shown for comparison. Fitted values (solid line) and standard errors (dotted lines) derived from Generalized Additive Mixed Models. !

Bebber DP, Ramatowski MAT & Gurr SJ. 2013. Crop pests and pathogens move poleward in a warming world. Nature Climate Change. doi: 10.1038/NCLIMATE1990