Conservation of PlantsMartin Hermy, Department of Earth and Environmental Sciences, Katholieke Universiteit

Leuven, Leuven, Belgium

Olivier Honnay, Department of Biology, Katholieke Universiteit Leuven, Leuven, Belgium

Hans Jacquemyn, Department of Biology, Katholieke Universiteit Leuven, Leuven, Belgium

Rein Brys, Institute for Nature and Forest Research, Brussels, Belgium

Based in part on the previous version of this eLS article ‘Conservation ofPlants’ (2007) by Martin Hermy, Patrick Endels, Hans Jacquemyn andRein Brys.

Approximately 3.4% of the predicted total number of

species on Earth is plants. Plants and their communities

are an indispensable part of the Earth’s biosphere as

plants not only affect ecosystem functioning, but also

provide essential ecosystem services for the benefit of

humans. However, plants face many threats and current

extinction rates have been estimated to be 100–1000

times higher than those of the prehuman era. The five

most importantdriversofplantextinctionare: (1)habitat

loss and fragmentation, (2) introduction of exotic spe-

cies, (3) climate change, (4) overexploitation and (5)

pollution. For conservation plans to be effective, four

essential steps are needed to maintain viable plant

populations in the long term. These include assessment of

thebiological statusofa species,diagnosisof thecausesof

decline, prescription of management strategies that will

counterbalance the decline, and implementation of

management practices and further monitoring.

Introduction

Notwithstanding plants are crucial parts of life on Earththat interactwith and dependon the nonliving componentsof the planet (atmosphere, oceans, freshwaters, soils andtheir components), there is mounting evidence that moreand more plant species are threatened with extinction orhave already gone extinct. However, there is also growingawareness that plant species contribute to ecosystemfunctioning and health and provide important benefitsfor mankind and therefore represent an important targetfor conservation. The principal aim of plant conservation

is to maintain viable populations of plant species in thelong term and to prevent plant species from becomingextinct, either locally, regionally or globally. This articlesummarises the recent advances in plant conservation.First the authors provide new evidence that plantsare worth conserving, not only because they are beneficialfor ecosystems, but also because they provide importantbenefits for society. The authors briefly summarise thethreats plants are facing and finally outline some ideasregarding strategies and management tactics that mayimprove plant conservation actions. Evidence gatheredhere almost exclusively comes from vascular plant species.See also: Conservation Biology and Biodiversity; Con-servation of Biodiversity; Conservation of Populationsand Species

The Size of the World’s Flora and itsDistribution

The total number of plant species has recently been esti-mated approximately as 298 000 species (Mora et al., 2011).Currently, some 215 644 (72.6%) plant species have beendescribed, which is approximately 17%of all known specieson Earth (Figure 1). At the global scale, there is a clear lati-tudinal gradient in plant species richness, declining from theequator to the poles. However, latitude as such does notexplain species richness; it is a mere correlate of otherpotentially causal environmental and biotic factors such ashistorical disturbances, environmental stability, habitatheterogeneity, productivity, land area and interspecificinteractions.Most plant species are absent frommost placesfor most of the time. Yet the majority is clumped in theirdistribution. Using two basic criteria (the number of(endemic) species and degree of threat), Myers et al. (2000)showed thatapproximately 44%of all vascular plant speciesare confined to 25 areas (so-called hotspots), which com-prised only 1.4% of the Earth’s land surface. More in par-ticular, the tropicalAndes,Mesoamerica and theCaribbeancontain the highest plant diversity and therefore can beconsidered as the world’s most important plant biodiversity

Advanced article

Article Contents

. Introduction

. The Size of the World’s Flora and its Distribution

. Conservation of Plant Biodiversity: Why Should We

Care?

. Causes of Plant Species Decline and Extinction

. Population Viability Analysis

. Shortcuts for Defining Plant Conservation Priorities

. A Strategy for Plant Conservation at Local and

Landscape Scale

Online posting date: 15th August 2014

eLS subject area: Ecology

How to cite:Hermy, Martin; Honnay, Olivier; Jacquemyn, Hans; and Brys, Rein(August 2014) Conservation of Plants. In: eLS. John Wiley & Sons, Ltd:

Chichester.

DOI: 10.1002/9780470015902.a0003353.pub2

eLS & 2014, John Wiley & Sons, Ltd. www.els.net 1

hotspots. See also: Biogeographical Regions; LatitudinalDiversity Gradients; Plant Biodiversity

Conservation of Plant Biodiversity:Why Should We Care?

Plant biodiversity and functioning ofecosystems

Although there are also solid ethical arguments for speciesconservation for its own sake, increasing evidence that(plant) species diversity positively correlates with the effi-ciency of many ecosystem functions has provided con-servationists with additional, strong scientific argumentsfor biodiversity conservation. Ecosystem functions can bedefined as all ecological processes that mediate the flux ofnutrients, energy and organic matter through the environ-ment (e.g. primarybiomass production, nutrient cycling anddecomposition of dead biomass). Based on both empirical,mostly experimental, work and mathematical modelling,there is currently convincing evidence that the loss of plantspecies reduces both the efficiency of ecosystem functionsand the stability of these functions through time (Cardinaleet al., 2012). TheAmazon region, for example, does not onlyhost more than half of the world’s remaining tropical for-ests, it also regulatesmacroecological phenomena andoffersimportant contributions to buffering the negative con-sequences of climate change (Killeen and Solorzano, 2008;Wang et al., 2009). Recent research has further shown thatplant communities where species are evenly and distantlyrelated to one another are generally also more stable com-pared to communities where phylogenetic relationships aremoreclumped, indicating that greater evolutionarydiversitycan buffer ecosystems against environmental variation andlead to greater ecosystem stability (Cadotte et al., 2012).Furthermore, there is increasing evidence that maintainingdifferent ecosystem functions simultaneously, at multipleplaces and times, requires higher plant diversity than doesmaintaining a single process at a single place and time.

The most widely studied ecosystem function is primaryproduction. Primary production is the sequestration ofatmospheric carbon (CO2) into biomass, using the energyfrom the sun (photosynthesis). At least for this ecosystemfunction, it seems that the relation with plant diversity issaturating, implying that the loss of few species from anecosystem does not cause a strong reduction of biomassproduction. There are two equally important mechanismsbehind the diversity – productivity relationship. First,in plant diverse communities it is more likely to have at leastone very productive species (the ‘sampling’ effect or the‘super species’ effect), and second, complementarity betweenspecies in diverse communities increases the efficiency andtotal amount of resource capture (the ‘complementarity’effect). This effect becomes most apparent when speciesassemblages consist of distantly related species, indicatingthat evolutionary history and phylogenetic relationshipsbetween species contribute to ecosystem functioning(Cadotte et al., 2008; Cadotte et al., 2012; Cadotte, 2013).The latter thus demonstrates that phylogenetic or functionaldiversity ismore important thanplant taxonomicdiversity inmediating ecosystem functioning (Cadotte, 2013). Plantfunctional diversity can be quantified based on the diversityof traits of the plant species that are present in a community.Examples of such traits are rooting depth, plant height andleaf area index. Phylogenetic diversity can be measured in anumber of ways. A common measure (PD) is defined andcalculated as ‘‘the sum of the lengths of all those branchesthat are members of the corresponding minimum spanningpath’’ (Faith, 1992). Other measures are the mean nearesttaxon distance and the mean pairwise distance.

Plant biodiversity and ecosystem services

Besides directly affecting ecosystem functioning, plantsalso provide important ecosystem services. Ecosystemservices are the benefits that people obtain fromecosystemsand include (1) provisioning services such as food, geneticresources, building materials and water; (2) regulatingservices such as plant pollination, flood and disease con-trol; (3) cultural services such as spiritual, recreational and

0 20 00 000 40 00 000 60 00 000 80 00 000 100 00 000

Animalia

Chromista

Fungi

Plantae

Protozoa Predicted Catalogued

Figure 1 Currently, catalogued and predicted total number of species on Earth. Data from Mora et al., 2011.

eLS & 2014, John Wiley & Sons, Ltd. www.els.net2

Conservation of Plants

cultural benefits and (4) supporting services, such asnutrient cycling and soil formation, that maintain theconditions for life on Earth (Figure 2; MEA, 2005).Although some of these ecosystem services are relativelyindependent of the species richness of the ecosystems thatprovide them, it is generally acknowledged that species richecosystems can provide more and more stable services tosociety (Cardinale et al., 2012). More and more evidence isbecoming available that also suggests that the phylogeneticdiversity – a measure of biodiversity which incorporatesphylogenetic difference between species – of plant com-munities is related to the ecosystem functions it provides(Srivastava et al., 2012; Cadotte, 2013). In contrast to theoften experimentally demonstrated relationship betweenspecies richness and the functioning of ecosystems (seeabove), evidence for the relation between species richnessor phylogenetic diversity and ecosystem service provi-sioning is much more observational and thus correlative.There is, however, for example, convincing evidence thatforests and grasslands that are rich in tree and herbaceousspecies, respectively, produce more wood and fodder thanmonocultures (e.g. Vila et al., 2013). Furthermore, plantsin species rich ecosystems are less prone to pests and dis-eases, and these ecosystems are also more resistant toinvasion by exotic plant species. In other cases, the linkbetween ecosystem service provisioning and plant diversityis obvious. For example, chemical components of between10 000 and 20 000 plant species are currently used in med-icinesworldwide, andmanymore are orwill be screened formedicinal usage in the future. Between 1986 and 2006, notfewer than 60 wild plant species (so called crop wild

relatives) have contributed more than 100 beneficial traits,mainly related to disease resistance and abiotic stress tol-erance, to 13 major crops, including wheat, rice, tomatoand potato (Hajjar and Hodgkin, 2007). It has been esti-mated that 30%of the increase in crop yields since 1945 hasbeen achieved through crossing with wild relatives, repre-senting a worldwide value of US$115 billion per year.See also: Conservation Biology and Biodiversity

Threatened plant species

Humans tend to value rarity as a valuable asset, which isalso true for rare and threatened species. Conservationiststraditionally consider rarity to be a key criterion forecological evaluation and for defining management prio-rities. Rare species are, therefore, still an important partof recent evidence-based approaches to biodiversity ana-lysis, prioritisation and conservation (the biodiversityaudit,Dolman et al., 2012).Rarity as suchmaybe a naturalphenomenon. A plant species may be rare because (1) itsgeographical range is narrow, (2) its habitat range is nar-row due to specialisation or (3) local populations, evenwhere they do occur, are small. While human activitiesincrease the extinction risk of these naturally rare species,rarity as such of many species also originates fromincreasing human impact. As a consequence, current ratesof extinctions are estimated to be 100–1000 times higherthan those of the prehuman era (Thomas et al., 2004;MEA,2005). Using a random set of 1500 plant species from 7000plant species drawn from the five major plant groups andassessed against the IUCN Red list index categories and

• Food production • Nutrient cycling

• Soil formation

• Primary production

• Habitat provision

• Fresh water• Wood and fiber• Fuel• Biochemicals• Genetic resources

• Educational

• Spiritual and religious

• Recreational and tourism

• Aesthetic

Provisioningservices

Supportingservices

Culturalservices

Regulatingservices

• Climate regulation

• Flood regulation

• Water purification

• Disease regulation

Figure 2 Ecosystems services refer to the benefits people obtain from ecosystems (adapted from WRI, 2003). Ultimately these are offered by plant species

diversity of which ecosystems do consist. Services are greatly affected by humans and their activities, the scale of which ranges from the local to more and

more even the global scale. Supporting services are necessary for the production of all other ecosystem services; this is clearly reflected in their central

position. Provisioning services are products obtained from ecosystems and their constituents. Regulating services are obtained from regulation of ecosystem

processes. Cultural services collect all nonmaterial benefits obtained from ecosystems.

eLS & 2014, John Wiley & Sons, Ltd. www.els.net 3

Conservation of Plants

criteria, scientists from Kew Gardens, IUCN NaturalHistory Museum (London) found that the plants on earthare as threatened asmammals with one in five plant speciesthreatened with extinction (ANON, 2012). Tropical rain-forest contains most of the threatened plant species andgymnosperms are the most threatened group. However, asonly approximately 4% of the total plant species pool hasbeen evaluated (Hilton-Taylor et al., 2009), this may bea serious underestimate. See also: Conservation Biology inAction: Case Studies; Modern Extinction

Causes of Plant Species Decline andExtinction

Plants face many anthropogenic threats, which may actsynergistically or independently on individual plantpopulations. This will result in reduced population sizes or,in theworst case, in direct destruction of plant populations.There are five major anthropogenic drivers of plant speciesloss: (1) habitat loss and fragmentation, (2) introduction ofexotic species, (3) climate change, (4) overexploitation and(5) pollution. Synergies among these extinction driversmay strengthen the effects of single-threat drivers (Brooket al., 2008).

1. Land use change was and still is the basic driver ofhabitat loss. Worldwide, 70% of the Mediterraneanforests, 75% of the temperate deciduous forest and60%of the tropical forestswere lost due tourbanisationand agricultural expansion (MEA, 2005). These landcover changesmay directly result in natural habitat lossand plant species extinction, or they may result in thefragmentation of the remaining natural habitats, whichimplies reduced habitat areas, increased spatial isola-tion of the habitats and increased edge/core ratios of theremaining habitat fragments. Small fragments cangenerally only harbour small plant populations, andsmall plant populations are more prone to extinctionthan large populations. This is because small plantpopulations lose genetic diversity through the processesof random genetic drift (resulting in a loss of allelesand reduced adaptability to a changing environment)and inbreeding (resulting in increased homozygosityand short term loss of fitness) (Honnay and Jacquemyn,2007). Inbreeding in plants can happen throughincreased selfing or through reproduction betweengenetically related individuals (biparental inbreeding).When the spatial isolation between small plant popu-lations is low, genetic diversity lost through inbreedingand genetic drift may be replenished through pollenor seed exchange between populations. The negativeeffects of small population size can thus be compen-sated by the positive effects of high connectivitybetween populations. Moreover, small plant popula-tionsmay suffer from reduced seed set due to decreasingvisits from pollinating animals, mainly insects and/orlimitation in mating partners (Aguilar et al., 2006). The

pollinator community and the behaviour of individualpollinators may also change in small populations,resulting in altered mating patterns, increased selfing,reduced seed set and decreasing reproductive success.Small populationsmay also bemore prone to extinctionthan large populations due to demographic stochasti-city. Even if average survival and birth rates wouldproduce positive population growth rates, chanceevents might push small population to further declineor extinction (Jeppsson and Forslund, 2012). Finally,the increased edge/core ratio of small habitat fragmentsdecreases the habitat quality of the edge throughchanges in microclimate (which is mainly relevant forforest habitats), and the influx of nutrients and pesti-cides from adjacent land use (e.g. agricultural land).

2. The introduction of exotic species may result in adecline of native species due to altered competitiveinteractions (Bjerknes et al., 2007) and hybridisationbetween exotic species and phylogenetically relatednative species. In intertidal freshwater marshes alongthe river Scheldt (Belgium), for example, Thijs et al.(2012) showed that the presence of Impatiens glanduli-fera (introduced in the nineteenth century from thewestern Himalayas) negatively affected pollinator visi-tation rates and seed set in the nativeLythrum salicaria.One commonly accepted mechanism for plant inva-sions is the enemy release hypothesis (Keane andCrawley, 2002). This means that the natural herbivoresor pathogens of the invading species are absent in thearea where the species was introduced, allowing its fastspread and the out-competition of native species.However, impacts of alien species are diverse, hetero-geneous and not unidirectional (Vila et al., 2011).

3. Climate warming has been identified as a major threatto plant species diversity. It directly affects growth,flowering andother aspects of plant performance. Plantwater relations are very vulnerable to extremes drivenby changes in temperature and precipitation, andheat waves and flooding have a stronger effect onphysiological processes than changing mean climatevariables (Reyer et al., 2013). Plant phenology (e.g. budbreak and flowering time), seems most affected bychanging climate means (e.g. Bertin, 2008). Phenolo-gical mismatches may be induced by climate change,for example, between plant flowering time and polli-nator activity (Ovaskainen et al., 2013). Because thefragmentation of many natural habitats and the lowdispersal and colonisation capacity of many plant spe-cies hampers northward migration, many species willbecome extinct because they cannot tolerate rapidlychanging local environmental conditions.

4. Overexploitation by picking of flowers or other parts ofthe plant for commercial or medicinal use obviouslyresults in decreased reproductive output, smallerpopulation size andmost likely in lower levels of geneticdiversity.

5. Finally, pollution mainly under the form of nutrientpollution, is strongly threatening plant diversity in

eLS & 2014, John Wiley & Sons, Ltd. www.els.net4

Conservation of Plants

many parts of the world. Through the burning of fossilfuels and large-scale application of agricultural fertili-sers, natural and seminatural ecosystems are con-tinuously being enrichedwith nitrogen and phosphorus(e.g. Bobbink et al., 2010). The specific effects on plantspecies are often complex and include direct toxicity,inhibition of seed germination, increased susceptibilityto herbivores and altered patterns of competition. Bothexperiments and field observations have provided evi-dence that this enrichment drives significant losses ofplant diversity. This is especially true for plant speciestypically found in nutrient poor seminatural grass-lands, resulting in local or even regional extinction.Similarly, changes in atmospheric carbon dioxide con-centrations may directly change the competitive bal-ance between species that differ in rooting depth,photosynthetic pathway or woodiness. See also: Bio-diversity – Threats; Biological Control; BioticResponseto Climatic Change

Population Viability Analysis

Demographicmodels represent powerful tools to assess thebiological status of populations of endangered plant spe-cies and to propose management tactics aiming atincreasing their long-term viability. These models haverelied heavily on matrix models, which have a long tradi-tion in conservation biology (Caswell, 2001; Crone et al.,2011), but more recently integral projection models havebeen proposed as a useful alternative to adequately modelpopulation dynamics of plant and animal species (Merowet al., 2014; Rees et al., 2014). These models use a con-tinuous variable rather than discrete stage classes to cal-culate the increase or decline of a population and can beused for species with complex life histories (Ellner andRees, 2006) and in deterministic and stochastic environ-ments (Rees and Ellner, 2009). Basically, each attempt toprotect endangered plant species from going extinct shouldconsist of four different steps (Caswell, 2001): assessment,diagnosis, prescription and prognosis. Assessment pro-vides an idea of population performance and normallyconsists of calculating a measure that tells whether apopulation is increasing or decreasing in size (i.e. thepopulation growth rate l). If a population is decreasing insize (l51), the next step will be to diagnose the causes ofdecline. This can be done by comparing multiple popula-tions, or one population sampled at different time intervalsusing life table response experiment analyses. These ana-lyses allow identifying the crucial life-cycle transitions thatcontribute most to the difference in growth rate betweenthe population of concern and some other population thatwe know is more sanguine. Once we know what is causingthe decline of a population, the next stepwill be to prescribemanagement tactics that aim to increase the populationgrowth rate. Ideally, management tactics will be mostsuccessful if they target life-cycle transitions that havethe greatest impact on population dynamics. Sensitivity

analysis or elasticity analysis will exactly do this: identify-ing the life-cycle transitions that have the greatest impacton l and thereforemake attractive targets formanagementintervention. Finally, population viability analysis (PVA)can be used to predict the faith of the population in the longterm. This analysis refers to a species-specific method ofrisk assessment that is frequently used in conservationbiology and is defined as the process that determines theprobability that a population will go extinct within a givennumber of years. Although the use of PVAs has heavilybeen criticised (Beissinger andWestphal, 1998;Ellner et al.,2002), it can be a useful tool to model population trajec-tories under different management scenarios (Crone et al.,2013) and therefore provide useful information on speciesviability. For example, direct destruction of habitats,which evidently is the most drastic threat to plant speciessurvival and generally results in the immediate extinctionof local populations, can be included in PVA models as acatastrophe with a large impact, but with low probability(Lande, 1988). See also: Conservation of Populations andSpecies

Shortcuts for Defining PlantConservation Priorities

From species to ecosystems

Effective conservation involves an assessment of the causesof environmental change, the implementation of practicestomanage or counterbalance those changes and preferablyfurther monitoring of the species or the ecosystem ofinterest. Clearly, it is practically not feasible tomonitor andmanage every aspect of biodiversity. Therefore, severalshortcuts have been proposed. First, the minimal viablepopulation (MVP) size concept can be used a general fra-mework tomake conservation decisions. AMVP is definedas the minimum population size at which a populationis likely to persist over some defined period of time witha given probability of extinction (cf. Shaffer, 1981).Although MVP sizes should not be considered as a magicnumber (Flather et al., 2011), the MVP concept remains auseful benchmark to prioritise conservation actions (Traillet al., 2010). A recent meta-analysis has shown that esti-mates of MVP sizes vary between 2512 and 15 992 indivi-duals (median: 4824) (Traill et al., 2007), suggesting that ingeneral population sizes of at least 5000 adult individualsare needed to maintain viable populations in the longterm. Second, instead of monitoring each species indivi-dually, a worthwhile alternative could be to focus on par-ticular plant species that are representative for a larger setof species with very similar life-history traits (Simberloff,1998). Such species are denoted by different termsdepending on their function or indicator value. (1) ‘Key-stone species’ infer that certain species have impacts onmany others often far beyond what might have beenexpected from their size, biomass or abundance. Thesemay

eLS & 2014, John Wiley & Sons, Ltd. www.els.net 5

Conservation of Plants

be species near the top of food webs or species that fulfil animportant key-function within an ecosystem, such as spe-cies that create an essential environment for many otherplants andanimal species.A tree species such as theAfricanbaobab (Figure 3a) in the African savannahs is a typicalexample of a keystone species. (2) ‘Umbrella species’ arespecies that need large areas of habitat or specific habitatconditions, so that saving them will automatically savemany other species (Figure 3b). Oenothera californica mayfunction as an example of the latter, as the species needslarge areas of sand dunes to establish persistent popula-tions and as it fulfils an important role in sand dune pro-tection in California. (3) ‘Flagship species’ are those thatcan anchor a conservation campaign because they arousepublic interest and sympathy. Both umbrella and flagshipspecies are often large vertebrate species, although certainplant groups such as impressive tree species or large flow-ered orchid species, such as Cypripedium calceolus (Figure

3c), may come close. Finally, (4) ‘Indicator species’ arebelievedor hoped to reflect (i) the status of other species in a

habitat or (ii) a chemical and/or physical change in orcondition of the environment. The occurrence of specificplant species or vegetation types often mirror the envir-onmental conditions dominating at a site, such as height ofthe groundwater table, soil type or air pollution. Certainspecies or certain species groups are more sensitive to dis-turbances or may be representative of more stable condi-tions, for example, ancient forest plant species, such asHyacinthoides non-scripta (Figure 3d), not only indicateancient forests, but also point to the continued presence –at least for centuries – of forest as a form of land use. Theirindicator values make them important target species forconservation. See also: Conservation of Populations andSpeciesMore recently, it has been suggested that conservation

should protect evolutionary distinct species and movetowards conservation goals that include the maintenanceof ecosystem functioning. Inclusion of evolutionary dis-tinctness has become an important target in present-dayconservation. However, the use of these concepts and

(a) (b)

(c) (d)

Figure 3 Examples of species that may function as (a) keystone species of African Savannahs, the African baobab (Adansonia digitata) (photograph: R.

Aerts) (Used by kind permission of Raf Aerts); (b) an umbrella species of the Eureka Active Desert Dunes (California), Evening primrose (Oenothera californica)

(photograph: T. Schweich) (Used by kind permission of Tom Schweich); (c) a flagship species of many European National Parks, reserves and/or

organisations, Lady’s slipper orchid (C. calceolus) (photograph: R. Brys) and (d) an indicator species of European ancient deciduous forests; Bluebell (H. non-

scripta) (photograph: R. Brys).

eLS & 2014, John Wiley & Sons, Ltd. www.els.net6

Conservation of Plants

particularly the criteria for choosing target species areoften disputable as a specific management strategy estab-lished for a particular species (e.g. flagship species) orgroup of species may be in conflict with others. Toaccommodate this, some have argued that an alternative,more global approach is required. The idea is that ifmanagement keeps particular habitats or ecosystemshealthy, it will enable all component species to thriveand survive. The latter points to a habitat or ecosystemapproach, which in many cases may prove beneficial tomany plant species. Recently, Dolman et al. (2012) pro-posed a biodiversity audit, which builds further on evi-dence-based conservation. Basically, it consists of amethodology that aims at adopting the most efficient andfeasible management interventions within a particulararea, using quantitative data on all species present in thatarea and considering the benefits and drawbacks forall stakeholders involved. It ideally requires extensiveknowledge on all species occurring in a conservation area,the involvement of specialists for all taxa and speciesprioritisation and involvement of an extensive stakeholdergroup, making it a complex and challenging procedure,which probably is only feasible for the best studied con-servation areas.

A Strategy for Plant Conservation atLocal and Landscape Scale

Altogether, an efficient plant conservation policy shouldhave four important pillars: it should (1) create space forplants; (2) improve environmental quality for plants, bothin the designated areas for conservation and in the sur-rounding landscape matrix; (3) develop a specific plantspecies conservation policy (usually through (1); this mayinclude an in situ and an ex situ component) and (4) enlargethe social basis for plant conservation through education,information and participation. The latter may be a pre-requisite for continued long-term support for conserva-tion. More so, the first three pillars implicitly containsociological, economic and ethical components. Althoughthese are very important, the authors here only focus onecological aspects.Owing to their immobile character, habitat loss is par-

ticularly disastrous for plants, as they disappear with theirhabitat. Consequently, the preservation of the remaininghabitats, both in and outside conservation units, and oftenthe enlargement of existing habitat fragments are a pre-requisite for any successful conservation strategy. In aneffort to counterbalance habitat destruction, large enoughhabitat areas need to be set aside as conservation units.Preservation of large habitats will prevent species lossthrough detrimental processes typically accompanyinghabitat fragmentation (see above). Such core areas mayfunction as ‘building blocks’ on which to base regionalrestoration efforts. They may also act as a source for(re)colonisation of restored but still unoccupied fragments.

Apart from habitat area preservation, maintaining orrecovering suitable habitat conditions is the next logicalstep to conserve or increase the viability of existing andemerging populations and communities. In case habitatconditions are degraded, additional management inter-ventions are often inevitable to maintain or restore therequired environmental conditions. In many remaininghabitat patches occurring in fragmented landscapes, acease of appropriate management has often increased thedominance of competitive plant species and has inducedspontaneous vegetation succession and, in forests, a highdegree of canopy closure. This mostly results in reducedplant species richness of specialist plant species which areof high conservation value. Management interventions,such as cutting, coppicing, mowing, sod cutting andeven top soil removal, can then be applied as a tool torestore habitat quality. Many of these practices aim atmitigating the effects of eutrophication which result fromatmospheric nitrogen-deposition or phosphorus run-offfrom adjacent agricultural land. However, as already sta-ted, the preservation of a base ecological quality (e.g.throughappropriate environmental legislation) outside theconservation units is equally essential, as it will reducenegative edge effects, typically affecting the edge zones ofhabitat fragments in an agricultural landscape matrix (seeabove). Therefore, sufficiently wide buffer zones should becreated to incorporate edge considerations into reservedesign andmanagement. Such buffer zones not only reducethe impact of abiotic factors, such as fertiliser input andherbicide drift, but may also slow down the invasion ofspecies associated with disturbed areas and/or invasivespecies.Preservation and/or an increase of habitat quality gen-

erally increase population size and flowering probabilitiesof plant species. The latter may enhance attractiveness topollinators and reduce limitation of compatible matingpartners, both of which can result in increased seed pro-duction rates. An increase in reproductive output willresult in increased recruitment and turn regressive popu-lations, which mainly consist of relict, often nonfloweringadult individuals, into vital populations where all lifestages are present. An increase in the number and densityof flowering individuals may further affect pollinatorbehaviour, because pollinator visitation times tend to beshorter at larger plant densities. This may in turn slowdown the degree of self-pollination and reduce inbreedingand associated inbreeding depression. If the limitationsto reproductive success can be reversed or avoided andif the environmental conditions allow seed germinationand establishment of new individuals, the perspectivesfor restoration and local population maintenance areconsiderable. See also: Pollination by Animals; Self-incompatibilityTo counterbalance the effects of habitat fragmentation

and to enlarge the functional connectivity among popula-tions, the establishment of ‘corridors or stepping stones’have been proposed. Increased connectivity may improveplant species persistence by enhancing among-population

eLS & 2014, John Wiley & Sons, Ltd. www.els.net 7

Conservation of Plants

migration through seeds and pollen flow. When localextinctions occur, corridors may also facilitate (re)coloni-sation of empty patches. We do know that corridorsfunction for mobile (animal) species, but for many plantspecies their functionality remains unproven. When afterthe restoration of habitat quality, recolonisation of plantspecies still does not occur, it is clear that dispersal lim-itation is the bottleneck, and that the artificial introductionof seeds or mature individuals may be considered as a lastresort, but not a guarantee for success (cf. Baeten et al.,2009). Whereas introductions and population re-enforce-ments are often still controversial (e.g. because they maycontribute to outbreeding depression), there are practicalframeworks available to assess the risks of these translo-cations (e.g. Weeks et al., 2011). Given that the impact ofclimate change on species distribution patterns is likely toincrease in the near future, conservation strategies shouldconsider protecting ‘conservation corridors’ that spanlarge environmental gradients in order to ensure that spe-cies can shift range distributions (Imbach et al., 2013;Nunez et al., 2013). In this context riparian corridors may,for instance, be effective in providing protection and/orrange expansions to both terrestrial and aquatic ecosys-tems. Also potential altitudinal corridors, such as theAndes, may provide important routes of escape for a largenumber of species. See also: Dispersal: BiogeographyFinally, endangered plant species may also be preserved

ex situ, for example, in seed banks or botanical gardens.Apart from their educational function, botanical gardensfulfil an important role in the ex situ preservation ofhighly endangered species, or of directly useful species, forexample, Crop Wild Relatives. Additionally they can beinvolved in (re)introduction programmes, playing a func-tional role in complementing in situ conservation. How-ever, there are alsomajor drawbacks associatedwith ex situconservation. These are associated with rapid loss ofgenetic diversity in ex situ populations and with the lack ofevolutionary adaptation to changing environmental con-ditions (such as climate warming) in these populations(Schoen and Brown, 2001).

References

Aguilar R, Ashworth L, Galetto L and Aizen MA (2006) Plant

reproductive susceptibility to habitat fragmentation: review and

synthesis through a meta-analysis. Ecology Letters 9: 968–980.

ANON (2012) Plants Under Pressure – A Global Assessment.

IUCN Sampled Red List Index for Plants. Royal Botanic

Gardens, Kew, UK. http://www.kew.org/science-conserva-

tion/search-rescue/mapping-plants/plants-at-risk/index.htm

(assessed 13.03.2014).

Baeten L, Hermy M and Verheyen K (2009) Environmental lim-

itation contributes to the differential colonization capacity of

two forest herbs. Journal of Vegetation Science 20: 209–223.

Beissinger SRandWestphalMI (1998)On the use of demographic

models of population viability in endangered species manage-

ment. Journal of Wildlife Management 62: 821–841.

Bertin RI (2008) Plant phenology and distribution in relation to

recent climate change. Journal of the Torrey Botanical Society

135: 126–146.

Bjerknes A, Totland Ø, Hegland S and Nielsen A (2007) Do alien

plant invasions really affect pollination success in native plant

species? Biological Conservation 138: 1–12.

Bobbink R, Hicks K, Galloway J et al. (2010) Global assessment

of nitrogen deposition effects on terrestrial plant diversity: a

synthesis. Ecological Applications 20: 30–59

BrookBW,SodhiNSandBradshawCJA (2008) Synergies among

extinction drivers under global change. Trends in Ecology &

Evolution 23: 453–460.

Cadotte MW (2013) Experimental evidence that evolutionary

diverse assemblages result in higher productivity. Proce-

edings of the National Academy of Sciences of the USA 110:

8996–9000.

Cadotte MW, Cardinale BJ and Oakley TH (2008) Evolutionary

history and the effect of biodiversity on plant productivity.

Proceedings of the National Academy of Sciences of the United

States of America 105: 17012–17017.

Cadotte MW, Dinnage R and Tilman D (2012) Phylogenetic

diversity promotes ecosystem stability.Ecology 93: S223–S233.

Cardinale BJ, Duffy JE and Gonzales A (2012) Biodiversity loss

and its impact on humanity. Nature 486: 59–67.

Caswell H (2001) Matrix Population Models, 2nd edn. Sunder-

land, MA: Sinauer Associates.

Crone EE, Ellis MM, Morris WF et al. (2013) Ability of matrix

models to explain the past and predict the future of plant

populations. Conservation Biology 27: 968–978.

Crone EE, Menges ES, Ellis MM et al. (2011) How do plant ecol-

ogists use matrix population models? Ecology Letters 14: 1–8.

Dolman PM, Panter CJ and Mossman HL (2012) The biodi-

versity audit approach challenges regional priorities and iden-

tifies amismatch in conservation. Journal ofAppliedEcology 49:

986–997.

Ellner SP, Fieberg J, Ludwig D and Wilcox C (2002) Precision of

population viability analysis. Conservation Biology 16: 258–261.

Ellner SP and Rees M (2006) Integral projection models for s

pecies with complex demography. American Naturalist 167:

410–428.

Faith DP (1992) Conservation evaluation and phylogenetic

diversity. Biological Conservation 61: 1–10.

FlatherCH,HaywardGD,Beissinger SRandStephensPA (2011)

Minimum viable populations: is there a ‘magic number’ for

conservation practitioners? Trends in Ecology & Evolution 26:

307–316.

Hajjar R and Hodgkin T (2007) The use of wild relatives in crop

improvement: a survey of developments over the last 20 years.

Euphytica 156: 1–13.

Hilton-Taylor C, Pollock CM, Chanson JS et al. (2009) State of

the world’s species. In: Vie J-C, Hilton-Taylor C, Stuart SN

(eds) Wildlife in a Changing World. An Analysis of the 2008

IUCNRed list of Threatened Species, pp. 15–41. Gland: IUCN.

Honnay O and Jacquemyn H (2007) Susceptibility of rare and

common plant species to the genetic consequences of habitat

fragmentation. Conservation Biology 21: 824–831.

Imbach PA, Locatelli B, Molina LG, Ciais P and Leadley PW

(2013) Climate change and plant dispersal along corridors in

fragmented landscapes ofMesoamerica. Ecology and Evolution

3: 2917–2932.

eLS & 2014, John Wiley & Sons, Ltd. www.els.net8

Conservation of Plants

Jeppsson T and Forslund P (2012) Can life history predict the

effect of demographic stochasticity on extinction risk.American

Naturalist 179: 706–720.

KeaneRMandCrawleyMJ (2002) Exotic plant invasions and the

enemy release hypothesis. Trends in Ecology & Evolution 17:

164–170.

Killeen TJ and Solorzano LA (2008) Conservation strategies to

mitigate impacts from climate change in Amazonia. Philoso-

phical Transactions of the Royal Society B-Biological Sciences

363: 1881–1888.

Lande R (1988) Genetics and demography in biological con-

servation. Science 241: 1455–1460.

MEA (Millennium Ecosystem Assessment) (2005) Ecosystems

and Human Well-Being. Washington: Island Press.

Merow C, Dahlgren JP, Metcalf CJE et al. (2014) Advancing

population ecology with integral projection models: a practical

guide. Methods in Ecology and Evolution 5: 99–110.

Mora C, Tittensor DP, Adl S, Simpson AGB andWorm B (2011)

How many species are there on Earth and in the Ocean? PLoS

Biology 9: e1001127.

Myers N, Mittermeier RA, Mittermeier CG, da Fonseca GAB

and Kent J (2000) Biodiversity hotspots for conservation

priorities. Nature 403: 853–858.

Nunez TA, Lawler JJ, Mcrae BH et al. (2013) Connectivity

planning to address climate change. Conservation Biology 27:

407–416.

Ovaskainen O, Skorokhodova S, Yakovleva M et al. (2013)

Community-level phenological responses to climate change.

Proceedings of the National Academy of Sciences of the USA

110: 13434–13439.

Rees M, Childs DZ and Ellner SP (2014) Building integral pro-

jection models: a user’s guide. Journal of Animal Ecology 83:

528–545.

Rees M and Ellner SP (2009) Integral projection models for

populations in temporally varying environments. Ecological

Monographs 79: 575–594.

Reyer CPO, Leuzinger S, Rammig A et al. (2013) A plant’s per-

spective of extremes: terrestrial plant responses to changing

climatic variability. Global Change Biology 19: 75–89.

Schoen DJ and Brown AHD (2001) The conservation of wild

plant species in seed banks. BioScience 51: 960–966.

Simberloff D (1998) Flagships, umbrellas, and keystones: is sin-

gle-species management passe in the landscape era? Biological

Conservation 83: 247–257.

Shaffer ML (1981) Minimum population sizes for species con-

servation. BioScience 31: 131–134.

Srivastava DS, CadotteMW,MacDonal AM,Marushia RG and

Mirotchnick N (2012) Phylogenetic diversity and the func-

tioning of ecosystems. Ecology Letters 15: 637–648.

Thijs KW, Brys R, Verboven HAF and Hermy M (2012) The

influence of an invasive plant species on the pollination success

and reproductive output of three riparian plant species. Biolo-

gical Invasions 14: 355–365.

Thomas CD, Cameron A, Green RE et al. (2004) Extinction risk

from climate change. Nature 427: 145–148.

Traill LW,BradshawCJAandBrookBW(2007)Minimumviable

population size: a meta-analysis of 30 years of published esti-

mates. Biological Conservation 139: 159–166.

Traill LW, Brook BW, FrankhamRR and Bradshaw CJA (2010)

Pragmatic population viability targets in a rapidly changing

world. Biological Conservation 143: 28–34.

VilaM, Carrillo-Gavilan A, Vayreda J et al. (2013) Disentangling

biodiversity and climatic determinants of wood production.

PLoS One 8(2): e53530.

Vila M, Espinar JL, Hejda M et al. (2011) Ecological impacts of

invasive alien plants: a meta-analysis of their effects on species,

communities and ecosystems. Ecology Letters 14: 702–708.

Wang J, Chagnon FJF, Williams ER et al. (2009) Impact of

deforestation in the Amazon basin on cloud climatology. Pro-

ceedings of the National Academy of Sciences of the USA 106:

3670–3674.

Weeks AR, Sgro CM, Young AG et al. (2011) Assessing the

benefits and risks of translocations in changing environments: a

genetic perspective. Evolutionary Applications 4: 709–725.

WRI (2003) Millennium Ecosystem Assessment Ecosystems and

Human Well-Being. A Framework for Assessment. London:

Island press.

Further Reading

Cook CN, Hockings M and Carter RW (2010) Conservation in

the dark? The information used to support management deci-

sions. Frontiers in Ecology and the Environment 8: 181–186.

Doak DF, Bakker VJ, Goldstein BE and Hale B (2014) What is

the future of conservation? Trends in Ecology & Evolution 29:

77–81.

Hooper DU, Adair EC and Cardinale BJ (2012) A global synth-

esis reveals biodiversity loss as a major driver of ecosystem

change. Nature 486: 105–108.

Kreft H and Jetz W (2007) Global patterns and determinants of

vascular plant diversity.Proceedings of theNationalAcademyof

Sciences of the USA 104: 5925–5930.

Maxted N, Kell S, Ford-Lloyd B, Dulloo E and Toledo A (2012)

Toward the systematic conservation of global cropwild relative

diversity. Crop Sciences 52: 774–785.

Nunney L and Campbell KA (1993) Assessing minimum viable

population size: demographymeets population genetics.Trends

in Ecology & Evolution 8: 234–239.

Pysek P, Jarosık V, Hulme PE et al. (2012) A global assessment of

invasive plant impacts on resident species, communities and

ecosystems: the interaction of impact measures, invading spe-

cies’ traits and environment. Global Change Biology 18: 1725–

1737

Rands MRW, Adams WM, Bennun L et al. (2010) Biodiversity

conservation: challenges beyond 2010. Science 329: 1298–1303

eLS & 2014, John Wiley & Sons, Ltd. www.els.net 9

Conservation of Plants