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 The hitchhiker’s guide to the greenery: estimating dynamics of 150 years of trade‐driven non‐native species introductions via plant material Corresponding Author: Matthew J. MacLachlan1 ([email protected]) Economic Research Service, United States Department of Agriculture, 355 E Street SW Washington, DC 20024 Phone: (510) 847‐9297 Michael R. Springborn ([email protected]) Department of Environmental Science & Policy, University of California, Davis 2104 Wickson Hall, One Shields Avenue, Davis, CA 95616 Andrew M. Liebhold ([email protected]) US Forest Service Norther Research Station 180 Canfield St., Morgantown, West VA 26505 Selected Poster prepared for presentation at the 2016 Agricultural & Applied Economics Association Annual Meeting, Boston, MA, July 31‐ Aug. 2 Copyright 2016 by [authors]. All rights reserved. Readers may make verbatim copies of this document for non‐commercial purposes by any means, provided that this copyright notice appears on all such copies. Thehitchhiker’sguidetothegreenery:estimatingdynamicsof150
yearsoftrade‐drivennon‐nativespeciesintroductionsviaplant
material
Matthew J. MacLachlan, Michael R. Springborn, Andrew M. Liebhold, and Takehiko Yamanaka
INTRODUCTION
•
Trade and its cargo facilitate the unintentional introduction of organisms. Unintentional introduction, establishment and spread of non‐native species can result in increased competition for resources and displacement of native species. •
Non‐native species often destabilize ecosystems, sometimes resulting in important ecological changes that negatively affect agricultural productivity, forestry, fisheries, tourism, property values and outdoor recreation.
•
Inadvertent movement of organisms with international trade is not rare. Liebhold, et al. (2012) examined import inspection records for live plant imports to the U.S. between 2003 and 2010, and found that 22,267 shipments were found to have at least one reportable insect pest or pathogen.
Trading partners’ geographic location is essential to evaluating the risk posed by imports. Some regions are intrinsically riskier because they contain more species capable of invasion or are ecologically similar to the importing nation.
The risk of an introduction of a non‐native species from imports can be mitigated, in part, through import bans or the implementation of costly phytosanitary measures and inspection of trade. OBJECTIVES
•
•
Estimate the risk of introducing a non‐native species from the importation of plant materials from each ecological regions. DATA
Data were collected from three sources. Non‐native species
Cumulative introductions of non‐native species by ecological region
We use a subset of data provided by Yamanaka et al. (2015) on discoveries of non‐
native hemipteran species within the United States. The Nearctic region—importers from this region include Canada and Greenland—is omitted because species from this region are considered native. ,
1
,
The time and search effort‐dependent annual probability of discovering a non‐native species 1
∀
.
1 exp 0
1
2
In period , the probability of discovering a previously undiscovered species introduced in period is 1
.
Thus the expected number of discoveries, , of species from region in period is the sum of the probability of discovery times the expect number of introductions in each year .
1
Log‐likelihood maximization is equivalent to minimization of
ln
1
1
ln
200
Probability of discovery
Probability of discovery when introduced in year u
150
0.025
100
0.02
50
0.015
0.01
Year
Afrotropic
Asian Palearctic
Australasia
Indomalaya
Neotropic
Oceania
European Palearctic
0.005
50,000,000,000
5,000,000,000
,
is the vector of estimated parameters and is the observed annual 50,000,000
5,000,000
500,000
50,000
5,000
500
1854
Afrotropic
European Palearctic
Oceania
1885
1913
Year
Asian Palearctic
Indomalaya
1944
1854
Imports
500,000,000
where is the region specific parameter that defines the risk of introduction for the first unit of trade in the first year and is estimated between 0 and 1. where , , , ,
discoveries. 250
0
where is the annual value of imported plant material, is a concave transformation, is the cumulative value of imports, captures attenuation of introductions from the exhaustion of the pool of potential invaders, —a 3rd order spline—captures non‐trade level/value factors and is a vector of vertical heights of the knots. We specify
,
1
300
Cumulative import values by ecological region (2015$)
We generally follow Costello et al. (2007) in jointly estimating the number of introductions into each region in year as a Poisson process
exp
350
0
Extend and improve estimation techniques for systems with delayed, probabilistic observations, particularly in the context of pest and pathogen introduction. MODELANDESTIMATION
400
Observed discoveries and regionally estimated discoveries and introductions
 A substantial increases in import value paired with a simultaneous decline in introductions in recent decades leads to a pronounced decline in estimated introduction in all regions. Attenuation is compounded by the decline in non‐trade level/value factors.  Substantial attenuation among historically significant exporting regions (e.g. Asian and European Palearctic regions); less among other regions (e.g. Australasia and Indomalaya)
1974
2005
Australasia
Neotropic
We compiled data on annual values of imports to the U.S. for the years between 1854 and 2014. The data was collated by country of origin, then aggregated to ecological region. Early import data (1854‐
1965) was collected and recorded by the U.S. Department of Commerce (and Labor), Bureau of the Census (Statistics), and is publicly available within printed annual reports (U.S. Secretary of the Treasury (1854‐1965). The latter one‐third of the dataset (1967‐2014) was obtained online from the USDA Foreign Agricultural Service’s Global Agricultural Trade System (GATS).
1913
1944
1974
u=1854
u=1874
u=1894
u=1914
u=1934
u=1954
u=1974
u=1994
Non‐trade level/value risk factors were particularly high prior to the turn of the 20st century, but declined through WWI. These factors increased again in the post WWII era, likely as a result of increased diversity among imported plant products—which are not captured by our modeling approach. 2005
The pattern of discovery is partially determined by the probability of discovery, which is itself a function of the year, the time since introduction, and effort. Our estimates suggest that the length of the lag and effort play important roles in discovery, while the year does not. Non‐trade level/value factors
10
8
6
4
2
0
1854
1885
1913
1944
1974
2005
CONCLUSIONS
• We compare non‐native species introductions with trade in a novel way, using datasets not previously compiled. Effort
We proxy search intensity—or effort—using the discoveries of all native Hemiptera species within the U.S. Annual data from 1758 through the present on discoveries of many species including those found in the Order Hemiptera are available through the Integrated Taxonomic Information System (ITIS). Lags between the initial discovery of a new species and its reporting are commonly observed are addressed through an averaging process. We apply a uniform probability of discovery on the reported year and the previous nine. 1885
Non‐trade factors
• Inclusion of new data in estimation requires a unique estimation approach that builds on a combination of preexisting empirical and theoretical modeling typically applied to non‐native species introduction.
Effort proxy derived from discoveries of native Hemiptera species
100
80
• The origins of imports are integral to the risk of introducing non‐native hitchhiker species. 60
40
• Our estimated trend of non‐value risk factors suggests that national control policies enacted in the early 20th century—as well as earlier local efforts—
effectively reduced the risk imposed by imports of plant materials. 20
0
1749
1762
1775
1788
1801
1814
1827
1840
1853
1866
1879
1892
1905
1918
1931
1944
1957
1970
1983
1996
2009
•
Due to potential delays in reporting discoveries, we limit our estimation to 150 years, 1854 – 2003. We estimate the annual introductions for each of the seven ecological regions shown in the map, excluding the Nearctic region. We observe
1854
1860
1866
1872
1878
1884
1890
1896
1902
1908
1914
1920
1926
1932
1938
1944
1950
1956
1962
1968
1974
1980
1986
1992
1998
2004
2010
•
RESULTS
The unintentional transport of biological agents is an undesirable side‐effect of otherwise beneficial international economic commerce. Economic connectedness has increased over time, and is expected to greatly expand with proposed trade agreements such as the Trans‐Pacific Partnership. Proxy value/# of species
•
Year
Effort Proxy
REFERENCES
ITIS‐smoothed
•
Economic Research Service, U.S. Department of Agriculture (USDA). The views expressed are those of the authors and should not be attributed to USDA.
•
•
Costello, C., et al. 2007. "Unintended biological invasions: Does risk vary by trading partner?" Journal of Environmental Economics and Management
54:262‐276.
Liebhold, A.M., et al. 2012. "Live plant imports: the major pathway for forest insect and pathogen invasions of the US." Frontiers in Ecology and the Environment 10:135‐143.
Yamanaka, T., et al. 2015. "Comparison of insect invasions in North America, Japan and their Islands." Biological Invasions: 1‐13.