Why Invasions Matter A Response to Some Contrarian Claims Anthony Ricciardi Redpath Museum and McGill School of Environment McGill University
Nature 474: 153 154 (09 June 2011)
Three claims by the contrarians Human-assisted invasions do not differ fundamentally from prehistoric ones. (Briggs 2013; Vermeij 2005; Brown & Sax 2004, 2005) Impacts on biodiversity are exaggerated. (Thomas 2013; Schlaepfer et al. 2011; Brown & Sax 2004, 2005) Species origins (native/non-native) are not relevant to conservation management. (Valéry et al. 2013; Davis et al. 2011)
Counter claims, supported by evidence 1. Modern invasions are a unique form of global change. 2. Invasions erode biodiversity and disrupt ecosystems. 3. Species origins matter, because evolution matters. 4. Higher invasion rates render ecosystems more difficult to manage.
Two opposing views of modern invasions A) Modern invasions = nothing new The magnitude & impacts of human-assisted invasions are similar to those in the fossil record. (Vermeij 2005; Brown & Sax 2004, 2005) Great American Faunal Exchange (3 million years ago)
Two opposing views of modern invasions A) Modern invasions = nothing new The magnitude & impacts of human-assisted invasions are similar to those in the fossil record. (Vermeij 2005; Brown & Sax 2004, 2005) B) Modern invasions = unprecedented global change The current mass invasion event is unique in scale and impact. (Ricciardi 2007; Cassey et al. 2005)
Colonization of the Great Lakes by invaders from the Black Sea region
American comb jellyfish (Mnemiopsis leidyi) in the Black Sea Anchovy catch (10 3 tons) Decline in Black Sea anchovy 1000 100 10 1 0.1 1984 86 88 90 92 94 Mnemiopsis expansion Year
Origins of non-native species in the Baltic Sea (~130 species in total) 12% 25% 27% 11% 16% Data from Baltic Sea Alien Species Database
New Zealand
Galapagos Gough Isld Hawaii Australia Great Lakes Caspian Sea Black Sea Species per year Estimated rates of invasion for various regions 100 Prehistoric 10 1 0.1 0.01 0.001 0.0001 0.00001 0.000001 Ricciardi (2007)
Galapagos Gough Isld Hawaii Australia Great Lakes Caspian Sea Black Sea Species per year Estimated rates of invasion for various regions 100 10 Prehistoric Modern 1 0.1 0.01 0.001 0.0001 0.00001 0.000001 Ricciardi (2007)
Global transportation systems Globaia.org
Enormous numbers of organisms are moved through global shipping 3-10 billion tonnes of ballast water moved annually. 1 liter contains: thousands of plankton, millions of bacteria & billions of virus particles. >5000 species carried by ships at any time. Ballast water being released from a cargo ship
.and through live trade Smith et al. (2008) Conservation Letters 1: 103 109 1.1 billion live fishes imported into U.S., 2000-2005
Differences between natural/prehistoric and human-assisted invasions Natural invasions Human-assisted invasions Frequency of long-distance Very low Very high dispersal events Invasions between Rare Common biogeographic realms Numbers transported Usually small Potentially enormous Mass colonization Episodic, regional Global, ongoing Potential for synergies Low Very high with other stressors
Counter claims, supported by evidence 1. Modern invasions are a unique form of global change. 2. Invasions erode biodiversity and disrupt ecosystems. 3. Species origins matter, because evolution matters. 4. Higher invasion rates render ecosystems more difficult to manage.
Proportion of modern animal extinctions in which invasions were a causal factor Global animal extinctions: IUCN Red List: Bellard et al. 2016 (62%); Clavero & Garcia-Berthou 2005 (54%) 54 62% Global fish extinctions: AMNH database: Harrison & Stiassny 2004 Global mammal extinctions: AMNH database; McPhee & Flemming 2004 (48%) IUCN Red List: Bellard et al. 2016 (69%) Global bird extinctions: Birdlife International 2000 (50%) Bellard et al. 2016 (60%) Global reptile extinctions: Bellard et al. 2016 48% 48 69% 50 60% 57%
Near total extinction of the American chestnut by chestnut blight fungus from Asia 800 million chestnut trees destroyed in ~50 years
Science (2011) 332: 41-42 From 2006 2012: 6 million bats killed by White Nose Syndrome in N. America
Impact of Varroa mites on honeybees parasites native to southeast Asia invaded western Europe, U.K., N. America, S. America, N.Z., Hawaii destroyed most wild honeybee colonies in the U.S. Mites on honeybee pupa
Non-native plants are 40 times more likely to be invasive than native plants Number of species 20000 18000 16000 <0.3% Non-invasive Invasive 6000 4000 12% 2000 Simberloff et al. (2012) 0 Natives Non-native
Non-native consumers cause more damage to prey populations than do native consumers Effect on native populations log e (X consumer / X control ) Stronger negative impact 0.5 0.0 P < 0.003-0.5-1.0 n=29-1.5-2.0 n=44 Native Non-native Consumer origin Paolucci, MacIsaac & Ricciardi (2013)
Invasion of Guam by the Brown Tree Snake (Boiga irregularis) Invasion of Lake Victoria by the Nile Perch (Lates niloticus) Caused 16 extinctions (birds, lizards, bats) Caused ~100 150 spp extinctions (endemic cichlids)
Frog abundance % lakes containing frogs Impact of exotic trout on frogs (Rana muscosa) in alpine lakes in California Knapp et al. (2001)
Frog abundance % lakes containing frogs Impact of exotic trout on frogs (Rana muscosa) in alpine lakes in California Knapp et al. (2001)
Evidence from invasive species eradications
The effect of Peacock Cichlid Cichla ocellaris on the food web of Lake Gatun, Panama herons & kingfishers adult Cichla young Cichla terrestrial insects phytoplankton benthic algae Before introduction After introduction Zaret & Paine (1973) Science
Number of mosquitoes Seasonal abundance of malarial mosquitoes near Lake Gatun 7000 5000 3000 1000 1969 1970 1971 Post-invasion 1968 Pre-invasion 0 Zaret & Paine (1973) Science Month
Counter claims, supported by evidence 1. Modern invasions are a unique form of global change. 2. Invasions erode biodiversity and disrupt ecosystems. 3. Species origins matter, because evolution matters. 4. Higher invasion rates render ecosystems more difficult to manage.
Number of high-impact species Number of high-impact invaders versus total number of invaders in aquatic systems 30 Y = 0.10 X R 2 =0.85, p=0.0001 25 20 15 10 5 Ricciardi & Kipp (2008) 0 0 25 50 75 100 125 150 175 200 225 Total number of invaders Slope = 0.10 ± 0.02 (95% C.L.)
Hypothesized transfer of botulism from invasive mussels to birds in the Great Lakes Impact: >100,000 fish-eating birds killed since 1999. Cause: Type-E botulism Round goby Waterfowl Zebra/quagga mussels Clostridium botulinum
200 175 150 125 100 75 50 25 0 1830 1850 1870 1890 1910 1930 1950 1970 1990 2010 1800 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 Cumulative number of invaders Rate of discovery of invaders in aquatic systems Great Lakes Ricciardi (2006); GLANSIS (2012) 100 75 Baltic Sea Baltic Sea Alien Species Database 50 25 0 220 200 180 160 140 120 100 80 60 40 20 0 San Francisco Bay 100 Carlton & Cohen (1998) 90 CIESM (2005) 1850 1865 1880 1895 1910 1925 1940 1955 1970 1985 2000 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 110 80 70 60 50 40 30 20 10 0 Mediterranean Sea
Expected Number of Synergistic Disruptions Predicted consequence of an unrestrained invasion rate Number of Invaders
Expected Number of Synergistic Disruptions Predicted consequence of an unrestrained invasion rate Number of Invaders
In this worldwide pooling of faunas and floras, some species get out of bounds as pests and disease, others are extinguished. Aldo Leopold, The Land Ethic, 1949