Literature review and meta-analysis of vegetationresponses to goat and European rabbit eradications on

islands

By Daniella Schweizer,* Holly P. Jones and Nick D. Holmes

AbstractIntroduced goats and European rabbits have caused devastating effects on island vegetation and many successful efforts to eradicate these introduced animals have taken place mainly since the 1950’s. Yet, a comprehensive review of vegetation response to goat and rabbit eradications is lacking. We conducted a literature search for articles on vegetation assessments before and after eradications. We conducted two kinds of reviews of species richness and cover response to eradication: a literature review for studies that provided qualitative or species-by-species responses to eradications and a meta-analysis on quantitative vegetation cover and species richness data. A key finding from our literature search was a significant information gap in the reporting of vegetation responses after eradication. Out of over 200 successful island eradications that have been conducted since the 1800’s, we found only 23 eradication studies that met our criteria for inclusion in the present analysis. Plant richness and vegetation cover increased more often than they decreased after eradication. Results varied according to region, herbivore type, habitat andvegetation type suggesting island specific circumstances influence responses. The effect of eradication on sub Antarctic tundra species richness and on tropical vegetation percent cover was higher than for other types of vegetation. Few cases differentiate responses of native versus exotic plant species, despite native biodiversity protection being one common goal of introduced herbivore eradication. We strongly recommend before and after eradication vegetation monitoring to understand how island ecosystems respond to eradication. Continuous monitoring would provide guidance on whether active restoration strategies need to be implemented to recover key native species and on the development of a general model of expected vegetation response, which is an integral first step to accelerate our predictive ability of vegetation responses.

*Corresponding Author E-mail: daniellaschweizer@gmail.com

Pacific Science, vol. 70, no. 1November 12, 2015 (Early view)

Introduction

Islands represent only 3.6% of the terrestrial surface, yet they harbor 9.5 times higher plant

richness than continents (Kier et al. 2009). Habitat destruction, overexploitation and introduction

of novel predators and competitors severely impact island biota (Sadler 1999, Blackburn et al.

2004). Two of the most widely introduced mammalian herbivores on islands are European

rabbits (hereafter, rabbits; Oryctolagus cuniculus) and goats (Capra hircus), which have caused

devastating effects on native insular vegetation (Gillham 1963, Rudge and Campbell 1977,

Coblentz 1978, Armstrong 1982, Fernández and Sáiz 2007). Rabbits can adapt to many habitats,

have high reproduction rates and a varied diet, which allows them to overgraze and reduce or

eliminate island vegetation when they are introduced to islands (Courchamp et al. 2003). Goats

also have a generalist diet, leading to widespread overgrazing on islands. For example, on Volcan

Alcedo (Isabela Island, Galápagos), a rapid increase in introduced goat populations led to large

scale deforestation, and conversion of forest and scrub to grasslands (Desender et al. 1999).

Goats and rabbits have the potential of dispersing and increasing exotic plant species, thus

significantly altering plant composition and diversity on islands (Parker et al. 2006). For

example, rabbits increased the seed shadow of the introduced opium poppy, Papaver

somniferum, via endozoochory on Robinson Crusoe Island (Fernández and Sáiz 2007). Other

direct effects include destruction of nesting habitat by trampling, or competing for nesting

burrows with seabirds (e.g.Young 1981, Cruz and Cruz 1987). Introduced goats and rabbits can

also have indirect effects by providing food for other introduced animals and altering food webs

via trophic cascades. On Macquarie Island, rabbits were an important food source to feral cats

until they were eradicated (Bergstrom et al. 2009).

The negative effects of introduced goats and rabbits on island ecosystems have spurred concerted

efforts to remove these species where feasible. Since the 1800’s there have been at least 90

2

successful rabbit eradications and 147 successful goat eradications on islands (Fig 1). An

eradication campaign is deemed successful when all the individuals of the target species are

removed from the island. Methodology and efficacy have been improving steadily through the

years, leading to an almost continuous increase in the number of eradications of goats and rabbits

through time (Myers et al. 2000, Campbell and Donlan 2005,Clout and Russell 2006, Carrion et

al. 2011,DIISE 2014).

<< Fig. 1 near here >>

One of the aims of herbivore eradications is to restore native island vegetation (Campbell and

Donlan 2005). However, a global synthesis of vegetation responses to herbivore eradications is

currently lacking, therefore drawing general conclusions about the ability of herbivore

eradication to restore island vegetation remains difficult. We performed a narrative review of

articles providing qualitative measures of vegetation response to goat and rabbit eradication on

islands and a meta-analysis on those publications that reported quantitative measures on

vegetation cover and richness. In cases where a single study provided qualitative and quantitative

information, we employed them for both the narrative review and the meta-analysis. We

restricted the analysis to successful eradication of goats and rabbits because these two

herbivores have been the most widely introduced and successfully eradicated worldwide (DIISE

2014).

In addition to herbivore type, we evaluated quantitative vegetation responses to eradication

grouped by geographic region, habitat type, vegetation origin, time between eradication and

assessment and time since herbivore introduction. We expected a weaker plant species response

on islands in cold climates with tundra vegetation. Tundra vegetation do not recover well from

herbivory (Chapuis et al. 2003, Anderson et al. 2006). We expected exotic plant species to be

more resilient than native plant species to herbivore eradication. Many exotic plant species, such 3

as grasses, likely evolved under herbivory pressure on mainland environments, thus being able to

sustain populations under and recover from grazing (e.g. Holgrem 2002). We hypothesized

vegetation richness and cover would be positively related to time between eradication and

assessment, as plants would have had more time to recover. However, we expected an increase in

plant species richness and cover to be negatively related to time the island had been invaded,

since plants would have been subjected to grazing pressure for longer and thus take longer to

respond.

MATERIALS AND METHODS

We selected all islands on which successful, whole island, eradication events had been conducted

using the Database of Island Invasive Species Eradications (DIISE 2014). This database records

information on current and historical eradications of introduced species on islands. At the time of

the review, the information in the database was current up to April 2013.

We searched ISI Web of Science and Google Scholar using the following search terms: 1) goats,

rabbits, AND 2) eradication, AND 3) islands, AND 4) vegetation, plants. We searched all the

possible combinations of those terms, using one word from each group in the searches. We also

searched for articles by the island names found in the DIISE in combination with the search

terms above. We gathered relevant citations found in the articles as well and supplemented our

web search by reviewing the Proceedings of the International Conference on Island Invasives

hosted by the IUCN in 2002 and in 2011 (Veitch and M.N. 2002,Veitch et al. 2011). We looked

for references on goat impacts on island vegetation in the publications listed on Appendix 1 of

Campbell and Donlan (2005). In addition to the search of published data, we contacted experts

from the main regions where eradications have been conducted, namely, Australia, New Zealand,

the Galápagos, and the Pacific in an effort to gather unpublished literature. We selected all

articles that provided before and after accounts of vegetation response. We focused on unassisted4

vegetation responses and excluded islands where revegetation had been conducted after

eradication. This excluded one study from Phillip Island, Australia (Coyne 2010).

Literature review

To conduct the literature review on vegetation responses to goat or rabbit eradication, we

gathered information from those articles that provided either a qualitative account of vegetation

response, by vegetation type (e.g. either herbaceous or woody) or listed the responses on a

species-by-species basis. We extracted the information separately for each species for studies that

listed specific species' responses. Therefore, we had many entries for a single study. We

summarized the responses of vegetation cover and richness as either positive or negative and

grouped them by vegetation type (e.g. herbaceous or woody), vegetation origin (native or

exotic), type of herbivore (goats or rabbits), and presence of other mammalian herbivores.

Meta-analysis

We ran the meta-analysis on our two dependent variables - percent cover and richness -

separately. The response of vegetation to eradication was analyzed using response ratios as a

common measure of the effect (Chao et al. 2006). The response ratio was calculated as:

where Xt is the metric of vegetation richness or percent cover after the eradication and Xc is the

same metric before the eradication. We estimated the cumulative mean effect size of eradication

on vegetation richness and cover. The cumulative effect size of a sample of studies is a weighted

average of the effect size of all studies combined. The weight of the ith study is the reciprocal of

its sampling variance (1/vi) (Rosenberg et al. 2000).

5

In our case, however, three out of seven studies that reported species richness were missing

sample sizes, and only two reported sample size and standard deviation. Two reports on species

percent cover out of seven were missing sample size and standard deviations. Therefore, we ran

an unweighted model using sample size of 10 and standard deviation of 1 to maximize the data

we could use for the analysis (Osenberg et al. 1999). The cumulative effect size varies between

-∞ and ∞, with 0 meaning no effect of eradication on the vegetation, positive values a positive

effect of eradication on vegetation and negative values a negative effect (Rosenberg et al. 2000).

We estimated 95% bias-corrected, bootstrapped confidence intervals around the cumulative

effect sizes by drawing 5000 randomizations. Bootstrap confidence intervals are better estimates

of the confidence intervals for small sample sizes that are not normally distributed, which is

common in meta-analyses (Rosenberg et al. 2000). We estimated Rosenthal fail-safe tests to

determine the number of studies that would be required to overturn the results. A Rosenthal value

greater than 5n +10 is indicative of a reliable meta-analysis (Kotiaho and Tomkins 2002).

We calculated total heterogeneity (QT) to evaluate the variability in either richness or cover

present across studies. Total heterogeneity evaluates differences in effect sizes in the sample data

set by looking at how much the effect size of the ith study deviates from the cumulative effect

size. Significance of Q is estimated using a chi-square test with n-1 degrees of freedom, with n

being the total number of studies (Rosenberg et al. 2000). The null hypothesis states that all

effect sizes are equal and the significance of the heterogeneity value indicates that the variation is

greater than expected by sampling error and that other variables may need to be explored to

explain the variability.

In order to determine other explanatory variables that might account for the variation in effect

size among studies, one can group studies according to categories that one would hypothesize to

6

have differential effects on the dependent variable (in our case, the response ratio of either

vegetation richness or cover). We grouped studies by the following categorical variables: region

(e.g. Pacific, Sub-Antarctic), habitat type (e.g. xeric, tundra (arctic vegetation), tropical

(equatorial and subequatorial vegetation), vegetation type (herbaceous vs woody), vegetation

origin (native or exotic) and type of herbivore (goats or rabbits). We did not include potentially

important variables such as natural disturbances and history of human occupation due to the low

number of studies with differences in those variables.

Other introduced animals, in addition to goats and rabbits, were reported on six of the islands

(Great Island, San Benito West, Lehua Island, Sarigan, Selvagem Grande, San Clemente,

Macauley Island, Motukaraka; See Appendices 2 and 3), primarily rats (Rattus spp.) and pigs

(Sus scrofa). We acknowledge the confounding effect that the presence of rodents and other

introduced herbivore brings to estimating vegetation responses to goat and rabbit eradications.

However, we included those studies given data scarcity and grouped studies by presence or

absence of rodents and other herbivores to assess differences in vegetation response. We

analyzed the significance of the effect size using a categorical random model, that groups the

vegetation response in the categories mentioned and analyzes the data considering a true random

component of variation in the effect size among studies not solely attributed to sampling error

(Rosenberg et al. 2000). In addition to total heterogeneity we estimated the between-group

heterogeneity (Qb) that looks at the variability in the mean effect among categories versus

variability within categories (Rosenberg et al. 2000).

We evaluated percent cover and richness vegetation responses as a function of time the island

had been invaded (hereafter, time invaded), and time between the end of the eradication and the

vegetation assessment (hereafter, time since eradication). With continuous variables, the

relationship between the effect size and the independent variable is estimated through a least 7

squares linear regression that employs effect size (E), weight (we employed a sample size of 10

for all studies) and the value of the independent time variable (Xi). Standard errors of the slope

and the intercept are as:[1]

and the intercept as:[2]

The statistical significance is calculated by dividing the slope and the intercept by their standard

error, which gives a Z-score that is compared to the normal distribution. A significant response

indicates that the independent, continuous variable explains a portion of the effect size

(Rosenberg, 2000).

RESULTS

Out of over 200 successful island eradications conducted since the 1800’s we found 23

eradication studies that met our criteria for inclusion in the present analysis. For the literature

review we employed thirteen studies (Appendix 1). Ten studies reported a quantitative

assessment of vegetation richness and/or percent cover in response to eradication and were used

for the meta-analysis (Appendix 2). The articles represented a sample from widespread

geographies: the Atlantic, the Indian Ocean, the North Pacific, Pacific Baja, Australia, Chile, the

Galapagos, Hawaii, New Zealand, the Sub-Antarctic and the South Pacific.

Literature review

8

Eradication of rabbits increased vegetation cover in 80% of the plant species listed in the various

articles, while eradication of goats had a positive response in 74% of the species. There were no

records showing zero change in plant species vegetation cover after eradication. The literature

reported that percent cover of 80% (n=36) of the native species and of 100% (n=24) of the exotic

species listed increased after eradication. Herbaceous plant species showed a positive response in

percent cover after the eradication in 83% of the species while 70% of the woody plant species

increased. Species richness increased after eradication in all of the five studies that measured

species richness.

Meta-analysis: Richness

Eradication of herbivores had a low but positive effect on species richness. We did not find

significant variation in the effects of eradication on species richness either among the studies in

the dataset (QT=17.19, df=37, P =0.998) (Table 1) or when the data were grouped in categories

(Qb=5.75, df=12, p =0.928).

The eradication of goats significantly increased species richness, but rabbit eradication did not

show a significant effect (Fig. 2a). There were only two studies (Carnac and San Clemente

Island) that distinguished the responses of native versus exotic vegetation and the effect was not

significant for either case (Fig. 2b). There was a significant and positive effect of eradication on

species richness for all regions and habitats (Fig. 2c and Fig. 2d). Vegetation richness showed a

positive response after eradication of goats and rabbits despite the presence of rodents and other

mammalian herbivores on some of the islands reviewed (Fig 2e).

The effect of eradication on vegetation richness increased with time invaded (regression

coefficient= 0.0005, p<0.02), but not as a function of time since eradication. Some of the

variables dropped from the analysis due to there being only one study in that category or to the 9

lack variation among the studies. We obtained a fail-safe number of 451 studies, which suggests

the results were robust.

<< Fig. 2 near here >>

Meta-analysis: Percent cover

Eradication of goats and rabbits had a positive effect on vegetation percent cover. The total

heterogeneity value was not significant indicating that studies were not different from each other

(Qt=60.22, df=61, p = 0.504; Table 1). Similarly, effect sizes between variables in the categorical

analysis also did not differ significantly (Qb=3.43, df=12, p = 0.992).

<< Table 1 near here >>

Similarly to species richness, rabbit eradication did not significantly affect vegetation percent

cover, but goat eradication did (Fig. 3a). Native plant species showed a significant increase after

eradication whereas exotic species did not (Fig. 3b). The presence of rodents and other

mammalian herbivores on the island affected the vegetation cover change observed by the

eradication of goats and rabbits, however, the effect was still positive despite the presence of

rodents and other mammalian herbivores (Fig3c). Only in tropical habitats was the effect of

eradication on cover significant (Fig. 3d). Region was not included in the analysis due to low

sample size (less than 2 cases). Time invaded was not a significant variable explaining the effect

of eradication on vegetation cover (p>0.05), and time since eradication decreased the size of the

effect of eradication on percent cover (regression coefficient= -0.0217, p<0.00001). A fail-safe

number of 346 studies showed that the results were robust despite the low sample size.

<< Fig. 3 near here >>

10

DISCUSSION

Eradication of introduced vertebrates is regarded as a powerful tool to promote biodiversity

conservation (Bellingham et al. 2010a). However, impacts to island vegetation post-eradication

have not been consistently evaluated. From over 200 goat and rabbit eradications conducted

since the 1800’s on islands worldwide, we found only 23 studies that met our criteria for

inclusion either in the literature review or in the meta-analysis. We may have missed some

literature due to inherent limitations of the search engine, or to papers that had not been

published in indexed journals, but our search was extensive. The information gap that exists in

vegetation monitoring before and after eradications on islands has been highlighted elsewhere

(McEachern et al. 2009). Despite the low number of studies found, this study represents a first

attempt to consolidate information on vegetation responses to eradication of goats and rabbits,

which we hope will lead to further vegetation monitoring and thus more powerful analyses in the

future.

In both the literature review and the meta-analysis, we found plant richness and percent cover

increased after goat and rabbit eradication more often than they decreased. The literature review

showed more species increasing in percent cover than decreasing after both goat and rabbit

eradication (74% and 80% of the cases, respectively). This contrasts with results obtained in the

meta-analysis, which suggested no effect of vegetation cover after rabbit removal, a result we

suggest as idiosyncratic to the small sample size. The rabbit is a significant pest where

introduced, with many examples of the negative effects of rabbits on island vegetation, and on

positive effects of rabbit eradication or control (e.g., Bried et al. 2009, Olivera et al. 2010, Shaw

et al. 2011, Scott and Kirkpatrick 2013).

Determining the response of native versus exotic vegetation is of management relevance because

it can help assess if the goal of native species protection was met and identify any subsequent 11

management action required (e.g. revegetation, or exotic species control). Though we predicted

that exotic plant species might respond more positively than native plants to eradication, the

literature review showed that the percent cover of over 80% of both native and exotic plant

species listed in the different articles increased after eradication, suggesting similar responses.

Within our meta-analysis we had too small a sample size (n=2) to robustly distinguish whether

the effect of eradication was stronger on native versus exotic species, leaving us unable to

quantify any potential differences between native and exotic responses. However, several

narrative accounts identify exotic plant species increase after goat and rabbit eradication, with

various effects on the ecosystem such as outcompeting natives (Kessler 2002, Courchamp et al.

2003, Russell et al. 2005,, Hata et al. 2010, Weller et al. 2011). The literature reviewed

highlighted that plant species subject to more intense introduced goat or rabbit grazing tend to

have a stronger positive response following eradication (Donlan et al. 2002, Bellingham et al.

2010b, Eijzenga 2011). If these species are exotics they can experience a population explosion

after eradication.

There is evidence of preferred grazing, and therefore spread of exotic species by introduced

herbivores, such as bison on Santa Catalina Island, California (Constible et al. 2005). Three years

following rabbit eradication on Lehua Island, Hawaii, a 112% increase in exotic vegetation was

recorded versus a 34% decrease in native vegetation (Eijzenga 2011). The removal of goats from

the Sarigan Islands led to the explosion of the vine, Operculina ventricosa, which now covers

part of the island as an uninterrupted carpet (Kessler 2002). On the other hand, goat eradication

has led to dramatic endemic species recoveries in some cases. For example, the endemic

Guadalupe cypress (Callitropsis guadalupensis) rapidly increased seedling recruitment following

goat eradication (Garcillan et al. 2009). These case studies suggest that responses of native and

exotic vegetation may be variable. Seed bank surveys and introduced herbivore feeding

12

preference studies would allow predictions about whether herbivore removal could lead to an

increase in exotic population sizes that would need additional control.

Effect sizes grouped by geographic region and habitats showed variable results. Species richness

showed a positive response after eradication in all regions and vegetation types, contrary to our

prediction that there would be weaker responses in species richness in colder climates. Percent

cover only increased following herbivore eradication in tropical habitats, but mainly of exotic

grass and shrub species (North et al. 1994, Martin et al. 2008, Eijzenga 2011). Tropical islands

are vulnerable to plant invasion mainly due to two interacting processes: high net resource

availability and poor competitive ability of native species (Denslow 2003). Thus it appears that

the removal of the introduced herbivore in tropical islands releases exotic species from grazing

pressure with their consequent increase in percent cover at least during the time span of the

revised studies.

Vegetation on islands where rodents or other introduced mammalian herbivores/omnivores were

present along with goats or rabbits showed a positive response from the removal of grazing

pressure. Rats as omnivores can affect vegetation through herbivory or granivory, and are

capable of dietary shifts if their main resource becomes temporarily unavailable (Campbell and

Atkinson 2002, Caut et al. 2008). We acknowledge that the presence of other mammalian

herbivores, along with goats and rabbits, is a confounding variable. However, for most islands

were other herbivores were present we could attribute the vegetation responses to the eradication

of the herbivores of interest, goats or rabbits, due either to their higher number or that authors

directly linked the vegetation responses to the removal of goats or rabbits (Donlan et al. 2002,

Donlan et al. 2003, Chapuis et al. 2004, Martin et al. 2008, Wylie 2012). More studies on the

interactions between introduced herbivores and on any potential herbivore release that removing

13

one but not all introduced species on an island might lead to are needed to better predict the

consequences of single species eradication on islands with multiple introduced species.

Long-term monitoring of vegetation would help to evaluate whether the patterns after eradication

seen in our analysis continue over the long term. Our meta-analysis suggests that time since the

island had been invaded and time between eradication and assessment were significant

covariables in the effect of eradication on species richness or percent cover, respectively.

However, the effect of time was contrary to our expectations. We expected time the island had

been invaded to reduce the response of vegetation, however it increased the effect of eradication

on species richness and was not a significant covariable for variations in percent cover. We

thought time between eradication and vegetation assessment would lead to an increase in the

effect size of the vegetation response, but it was not significant for richness and decreased the

effect observed on vegetation cover. These results highlight the importance of continuous

monitoring of vegetation as species composition and percent cover can be very dynamic and

assessments at different times after eradication may lead to different, unexpected, results.

Nevertheless, practitioners should recognize and plan for the possibility that island vegetation

exposed to relatively recent invasions may respond differently than vegetation that has endured

introduced herbivores for longer periods of time.

Eradication of introduced mammals from islands is best contextualized as a baseline

conservation activity towards achieving broader restoration goals. As an example, eradication of

introduced goats and rabbits from islands reduces grazing pressure on plant species. However,

other restoration techniques may be required in order to fully realize biodiversity protection

goals, such as endangered species protection, revegetation or habitat creation (e.g. Letman 2008).

Concurrent eradication of all introduced plants and animals may be required in places were other

introduced species besides goats and rabbits exist to avoid unintended consequences of single

14

species eradications such as the population release of other introduced species (e.g. Lehua Island,

Eijzenga 2011). Planning for, and understanding responses to herbivore eradication should be

viewed in a whole ecosystem context (Zavaleta et al. 2001), with the monitoring of native and

exotic species response informing subsequent adaptive management.

A general model of expected vegetation response to eradications should be paired with species-

specific approaches for important native or endemic species that managers seek to restore, and

should account for potential trophic interactions with both native and exotic species post-

eradication (Veitch and Bell 1990, Zavaleta et al. 2001, Courchamp et al. 2003 , Tetsuto et al.

2011). Our findings in both the literature review and meta-analysis will be strengthened and

further clarified with future extensive monitoring efforts. Several locations have been the focus

of extensive vegetation monitoring assessments, including the California Channel Islands and the

Galápagos Islands. Two long-term studies of vegetation response before and after herbivore

eradication, Donlan et al. (2002) and Donlan (2003), represent study approaches that should be

repeated elsewhere.

ACKNOWLEDGEMENTS

We acknowledge and thank Island Conservation for providing the baseline data regarding

eradications of goats and European rabbits on islands worldwide (DIISE database). We would

also like to thank Dr. David Towns, Dr. Ole Hamann, Dr. Donald Croll, Dr. Bernie Tershy for

providing their expertise regarding the topic and guiding us to any unpublished sources of

information.

15

Table 1

Effect sizes and heterogeneity values for plant species richness and percent cover after goat and

rabbit eradication on islands. Results are based on an n of six studies for species richness and on

an n of eight studies for percent cover. The studies used are marked with * for richness and with

a + for cover on appendix 2. A CI bounding zero means the effect size is not significant. The p-

value corresponds to the significance of the total heterogeneity value.

16

Figure 1. Cumulative number of goat and rabbit eradications on islands by decade (Source

Database of Island Invasive Species Eradications)

17

Figure 2. Effect sizes (filled circles) and bootstrapped confidence intervals (error bars) looking atthe effect of herbivore eradication on vegetation richness, comparing various grouping variables. Effect sizes are significant if the confidence interval does not bound zero. A positive effect size means that eradication increased species richness, and vice versa if the value is negative. The numbers above the error bars represent the sample sizes

18

Figure 3. Effect sizes (filled circles) and bootstrapped confidence intervals (error bars) looking atthe effect of herbivore eradication on vegetation cover, comparing various grouping variables. Effect sizes are significant if the confidence interval does not bound zero. A positive effect size means that eradication increased species cover, and vice versa if the value is negative. The numbers above the error bars represent the sample sizes

19

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27

Appendix 1. Literature employed in the systematic review. NA: not applicable.

Authors Year Title Islandgroup

Island name(size)

Typeherbivoreremoved

Alves et al. , 2011Return of endemic plant populations onTrindade Island, Brazil, with comments

on the fauna

TrindadeArchipelago

TrindadeArchipelago

(1040 ha)Goats

Barkla et al. , 2008

Homalanthus polyandrus(Euphorbiaceae) on Macauley Island,

southern Kermadec Islands, with noteson that island's vascular flora

KermadecIslands

Macauley(306 ha)

Goats

Garcillan et al. , 2009

Recruitment response of GuadalupeCypress (Callitropsis guadalupensis)three years after goat eradication on

Guadalupe Island

NAGuadalupe

Island(2439 ha)

Goats

Hamann, 2004Vegetation changes over three decades

on Santa Fe Island, Galapagos, EcuadorGalápagos

Santa FeIsland

(2413 ha)Goats

Appendix 1. Cont.

Authors Year Title Islandgroup

Island name(size)

Typeherbivoreremoved

Hamann, 1993On vegetation recovery, goats, and giant

tortoises on Pinta island, Galápagos, EcuadorGalápagos Pinta Island

(5900 ha)Goats

Hata et al. , 2007Vegetation changes between 1978, 1991,

2003 in the Nakoudojima island that has beendisturbed by goats

BoninIslands Nakoudojima Goats

Henderson andDawson,

2009Alien invasions from space observations:

detecting feral goat impacts on Isla Isabela,Galapagos Islands with the AVHRR

GalápagosIsabelaIsland

(464000 ha)Goats

Kessler, 2002

Eradication of feral goats and pigs andconsequences for other biota on SariganIsland, Commonwealth of the Northern

Mariana Islands

MarianaIslands

Sarigan(500 ha)

Goats

Appendix 1. Cont.

Authors Year Title Islandgroup

Island name(size)

Type herbivore removed

Oliveira-Filho and Fontes, 2010

Successful eradication of the Europeanrabbit (Oryctolagus cuniculus) and housemouse (Mus musculus) from the island of

Selvagem Grande (Macaronesianarchipelago), in the Eastern Atlantic

Macronesia Archipelago

SelvagemGrande(340 ha)

Rabbits

Pierce et al. , 2010Atoll restoration in the Phoenix Islands,Kiribati: Survey results in November-

December 2009

PhoenixIslands

Rawakiisland (65 ha)

Rabbits

Robin et al. , 2011Remote sensing of vegetation coverchange in islands of the Kerguelen

archipelagoKerguelen

Islands

Rabbits

Russell et al. , 2005Ecological Survey of Motukaraka (Flat

Island), Beachlands, Auckland NA

Motukaraka(Flat) Island

(5.6 ha)Rabbits

Sykes and West, 1996New records and other information on the

vascular flora of the Kermadec islands

KermadecIslands

Raoul (2938ha) and

Macauley(306 ha)

Goats

References

Alves, R.J., Da Silva, N.G., Aguirre-Muñoz, A., 2011. Return of endemic plant populations on Trindade Island, Brazil, with comments on

the fauna. In: Veitch, C.R., Clout, M.N., Towns, D.R. (Eds.), Island Invasives: Eradication and Management. Proceedings of the International

Conference on Island Invasives. IUCN, Gland, Switzerland, pp. 259-263.

Barkla, J.W., Dilks, P.J., Greene, T.C., Griffiths, R., 2008. Homalanthus polyandrus (Euphorbiaceae) on Macauley Island, southern

Kermadec Islands, with notes on that island's vascular flora. N. Z. J. Bot. 46, 373-379.

Garcillan, P., Vega, E., Lopez-Reyes, E., 2009. Recruitment response of Guadalupe Cypress (Callitropsis guadalupensis) three years after

goat eradication on Guadalupe Island. In: C.C, D., Garcelon, D.K. (Eds.), Proceedings of the 7th California Islands Symposium, Institute of

wildlife studies, Arcata, CA.

Hamann, O., 1993. On vegetation recovery, goats, and giant tortoises on Pinta Island, Galapagos, Ecuador. Biodivers. Conserv. 2, 138-151.

Hamann, O., 2004. Vegetation changes over three decades on Santa Fe Island, Galapagos, Ecuador. Nord. J. Bot. 23, 143-152.

Hata, K., Suzuki, J., Kachi, N., 2007. Vegetation changes between 1978, 1991 and 2003 in the Nakoudojima island that had been disturbed

by feral goats. In: Kawakami, K., Okochi, I. (Eds.), Restoring the Oceanic Island Ecosystem: Impact and Management of Invasive Alien

Species in the Bonin Islands. Springer, New York.

Henderson, S., Dawson, T.P., 2009. Alien invasions from space observations: detecting feral goat impacts on Isla Isabela, Galapagos Islands

with the AVHRR. Int. J. Remote Sens. 30, 423-433.

Kessler, C.C., 2002. Eradication of feral goats and pigs and consequencesfor other biota on Sarigan Islands, Commonwealth of the Northern

Mariana Islands. In: Veitch, C.R., Clout, M.N. (Eds.), Turning the tide: the eradication of invasive species. Proceedings of the International

Conference on Island Invasives. IUCN, pp. 132-140.

Oliveira-Filho, A.T., Fontes, A.L., 2000. Patterns of floristic differentiation among Atlantic Forests in Southeastern Brazil and the influence

of climate. Biotropica 32, 793-810.

Pierce, R., Anterea, N., Coulston, G., Gardiner, C., Shilton, L., Taabu, K., Wragg, G., 2010. Atoll restoration in the Phoenix Islands, Kiribati:

Survey results in November-December 2009. In. EcoOceania Pty Ltd and Pacific Expeditions Ltd report for Government of Kiribati,

Critical Ecosystem Partnership Fund, NZ Department of Conservation, NZAID and

Pacific Invasives Initiative.

Robin, M., Chapuis, J.L., Lebouvier, M., 2011. Remote sensing of vegetation cover change in islands of the Kerguelen archipelago. Polar

Biol. 34, 1689-1700.

Russell, J.C., Cameron, E.K., MacKay, J.W.B., Dudley, J.L., Clout, M.N., 2005. Ecologica survey of Motukaraka (Flat Island), Beachlands,

Auckland. N.A.

Sykes, W.R., West, C.J., 1996. New records and other information on the vascular flora of the Kermadec islands. N. Z. J. Bot. 34, 447-462.

Appendix 2. Literature employed in the meta-analysis. The main criteria for selection of the articles was reporting quantitative vegetation percent cover or richness, before and after eradication of goats or rabbits.

Meta analysis

Authors Year Title Islandgroup

Island name(size)

Type herbivore removed

Abbott et al. , * 2000Long term change in the floristic composition

and vegetation structure of Carnac Island, Western Australia

NA CarnacIsland (19 ha)

Rabbits

Bellingham et al. , * 2010Disperser communities and legacies of goatgrazing determine forest succession on the

remote Three Kings Islands in New Zealand

Three KingsIslands

Great Island(407 ha)

Goats

Chapuis et al. , *+ 2004Recovery of native plant communities aftereradication of rabbits from the subantarcticKerguelen Islands, and influence of climate

change

KerguelenArchipelago

Ille Verte(148 ha) andIlle Guillou

(145 ha)

Rabbits

Donlan et al. , + 2003Islands, exotic herbivores, and invasiveplants: their roles in coastal California

restoration

Todos LosSantos

Todos LosSantos South

(100 ha)Rabbits

Appendix 2. Cont.

Meta analysis

Authors Year Title Islandgroup

Island name(size)

Type herbivore removed

Donlan et al. , + 2002Islands and introduced herbivores:conservation action as ecosystem

experimentationSan Benito

Islands

San BenitoWest

(350 ha)Rabbits

Eijzenga, + 2011Vegetation change following rabbit

eradication on Lehua Island, HawaiianIslands

NALehua Island

(112 ha)Rabbits

Martin et al. , *+ 2008Wildlife and vegetation surverys of SariganIsland. 2008 Technical Report # 14. CNMI

Division of Fish and Wildlife

MarianaIslands

Sarigan (500 ha)

Goats

North et al. , + 1994Changes in the vegetation and reptile

populations on Round Island, Mauritius,following eradication of rabbits

NARound Island

(169 ha)Rabbits

Appendix 2. Cont.

Meta analysis

Authors Year Title Islandgroup

Island name(size)

Type herbivore removed

Olivera et al. , *+ 2010

Successful eradication of the European rabbit(Oryctolagus cuniculus) and house mouse

(Mus musculus) from the island of SelvagemGrande (Macaronesian archipelago), in the

Eastern Atlantic

MacronesiaArchipelago

SelvagemGrande(340 ha)

Rabbits

Wylie *+ 2012Vegetation change on San Clemente Islandfollowing the removal of feral herbivores

ChannelIslands

SanClemente

Island(14713 ha)

Goats

* Denotes studies employed in the meta analysis of plant vegetation richness response to eradication+ Denotes studies employed in the meta analysis of plant vegetation percent cover response to eradication

References:

Abbott, I., Marchant, N., Cranfield, R., 2000. Long term change in the floristic composition and vegetation structure of Carnac Island,

Western Australia. J. Biogeogr. 27, 333-346.

Bellingham, P.J., Wiser, S.K., Wright, A.E., Cameron, E.K., Forester, L.J., 2010. Disperser communities and legacies of goat grazing

determine forest succession on the remote Three Kings Islands, New Zealand. Biol. Conserv. 143, 926-938.

Chapuis, J.L., Frenot, Y., Lebouvier, M., 2004. Recovery of native plant communities after eradication of rabbits from the subantartic

Kerguelen Islands, and influence of climate change. Biol. Conserv. 117, 167-179.

Donlan, C.J., Tershy, B.R., Croll, D.A., 2002. Islands and introduced herbivores: conservation action as ecosytem experimentation. J. Appl.

Ecol. 39, 235-246.

Donlan, C.J., Croll, D.A., Tershy, B.R., 2003. Islands, exotic herbivores, and invasive plants: their roles in coastal California restoration.

Restor. Ecol. 11, 524-530.

Eijzenga, H., 2011. Vegetation change following rabbit eradication on Lehua Island, Hawaiian Islands. In: Veitch, C.R., Clout, M.N.,

Towns, D.R. (Eds.), Island Invasives: Eradication and Management. Proceedings of the International Conference on Island Invasives. IUCN,

Gland, Switzerland, pp. 290-294.

Martin, G., Williams, L.L., De Cruz, J., Hawley, N., Vogt, S., Smith, B., Bourquin, O., Kremer, S., Kessler, C., 2008. Wildlife and vegetation

surverys of Sarigan Island. 2008 Technical Report # 14. CNMI Division of Fish and Wildlife. In: Martin, G. (Ed.). Division of Fish and

Wildlife.

North, S.G., Bullock, D.J., Dulloo, M.E., 1994. Changes in the vegetation and reptile populations on Round Island, Mauritius, following

eradication of rabbits. Biol. Conserv. 67, 21-28.

Olivera, P., Menezes, D., Trout, R., Buckle, A., Geraldes, P., Jesus, J., 2010. Successful eradication of the European rabbit (Oryctolagus

cuniculus) and house mouse (Mus musculus) from the island of Selvagem Grande (Macaronesian archipelago), in the Eastern Atlantic.

Integrative Zoology 5, 70-83.

Wylie, D.D., 2012. Vegetation change on San Clemente Island following the removal of feral herbivores. In, Geography. San Diego State,

San Diego, p. 77.