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Questions: Is rock climbing pressure, together with microtopographic conditions, disturbing cliff plant cover and composition? What are the climbing impacts on rock specialist and non-specialist species? Can a case-control approach, not previously implemented in cliff environments, offer additional value for actual and long-term ecological research? Location: Chulilla, Levante coast, Spain.Methods: We surveyed in situ nine rock climbing routes in order to examine differences in plant species richness and vegetation cover between unclimbed and climbed transects. To evaluate the effect of rock climbing on vegetation, we implemented a case-control methodology using the two zones immediately adjacent to common climbing routes as control points (i.e. unclimbed transects). Three quadrats of 3 m × 3 m were established at different cliff heights. All identified species were categorized as either specialized rock species or non-specialized rock species based on their habitat preferences from literature. Non-specialized rock species were further differentiated as either moderately associated with rocky environments or strict generalists. The rock climbing impact on each group of species was analysed using LMM. Results: Our results provide evidence of the effects of rock climbing on a Mediterranean cliff, which has received little attention so far. Significantly fewer generalist species were present on climbed compared to unclimbed transects, while specialized and moderately specialized rock species were not significantly affected by rock climbing intensity. Furthermore, while rock-specific and moderately specialized species could cope with microsite heterogeneity, areas with fewer cracks had significantly negative effects on generalist species. Conclusions: Moderate rock climbing activity on cliff environments might not reduce the presence of specialized rock-dwelling species; however, this activity inherently impacts the biodiversity of cliff ecosystems due to its large effect on generalist species. We recommend that future conservation studies account for the degree of species dependence on rocky habitats to better understand rock-climbing impacts in these singular ecosystems. According to our experience, the implementation of an adjacent case-control survey design for monitoring cliff vegetation can help improve and unify methodology for such studies, as this is still an underdeveloped field.
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Appl Veg Sci. 2018;1–9.  
Applied Vegetation Science
© 2018 International Association
for Vegetation Science
DOI: 10.1111/avsc.12355
An innovative vegetation survey design in Mediterranean cliffs
shows evidence of higher tolerance of specialized rock plants
to rock climbing activity
Martí March-Salas1| Miguel Moreno-Moya2| Gemma Palomar3,4| Pablo Tejero-Ibarra5|
Emily Haeuser6| Luis R. Pertierra7
Funding information
cialist and non-specialist species? Can a case-control approach, not previously
implemented in cliff environments, offer additional value for actual and long-term
Methods:We surveyed in situninerockclimbingroutesinorderto examine differ-
case-control methodology using the two zones immediately adjacent to common
wereestablished at different cliff heights.Allidentifiedspecieswerecategorizedas
as either moderately associated with rocky environments or strict generalists. The
cliff,whichhasreceivedlittleattentionsofar. Significantly fewer generalist species
were present on climbed compared to unclimbed transects, while specialized and
moderatelyspecialized rock specieswerenotsignificantlyaffectedby rock climbing
intensity.Furthermore, while rock-specificandmoderatelyspecializedspeciescould
the presence of specialized rock-dwelling species; however, this activity inherently
impactsthebiodiversityofcliffecosystemsdueto itslargeeffectongeneralistspe-
cies dependence on rocky habitats to better understand rock-climbing impacts in
these singular ecosystems. According to our experience, the implementation of an
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havereported disturbances to cliff vegetation fromthis increasingly
popular activity (Clark& Hessl, 2015; Lorite etal., 2017). However,
such disturbances to cliff plant communities remainto be assessed
ofspecies, togetherwiththeeffects ofmicrotopographicconditions
of the rock surface. In this regard, the review ofHolzschuh (2016)
pointedoutthe relevanceofthesephysicalandbiologicalfactorsfor
ings. Furthermore, specifically regarding biological factors, such as
adaptationofrockplant lifestrategies,theseeffects haveonlybeen
examined once and that sutdy focused on an alpine environment
munity, we examine all these effectsin a Mediterranean cliff plant
ditions,such asextremedryness, high erosion,intenseradiationand
species are able to grow, often including endemic species (Larson,
Matthes,&Kelly,2000). Cliff ecosystems sustain plant speciesspe-
cialized for dwelling within rock balconies, including chamaephytes
1951;Escudero, 1996). However,the life histories ofthese species
areremarkablydifferent;while specialistrockplantshavedeveloped
stress-tolerant traits to survive adverse abiotic factors (De Micco
&Aronne,2012;Surina & Martinčič, 2014), less adapted plants are
be more vulnerable to external impacts. Mediterraneancliff micro-
habitatsand their occupants contributesubstantiallyto biodiversity
intemperateregions, highlightingtheconservationvalue ofthecliff
like mountaineering, especially rock climbing, may endanger these
conservationpolicies have focused on theprotectionofbird repro-
&Larson, 2003; Rusterholz,Müller,& Baur,2004;Thiel & Spribille,
focusedon impactstothestructureand compositionof overallcliff
been noted (López-Pujol, Álvarez, Bosch, Simon, & Blanché, 2006).
effectsofrockclimbingoncataloguedendemic species,disregarding
plantcommunity structure and habitatdisturbances, partly because
rock climbing pressures (but see Müller etal., 2004). Furthermore,
inEurope,to our knowledge,thereareonlya few examples ofrock
assessments and reports within natural areas under management).
Moreover, scientific study of rockclimbing effects poses additional
challengesduetolimitedaccessibility,and this mayalso offer some
2016).Accountingforclimbing effectsovertime would alsoprovide
deeperknowledgeofthissystem, especially given the projected in-
consideration.Disturbance effects on habitats often occurgradually
Current effortsto study trampling impacts in areas with limited
adjacentcase-controlsurveydesignformonitoringcliffvegetationcanhelp improve
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accountforspatialcomponents, itisnecessarytosamplealongrock
route,it ispossibletoexamine the ecologicalimpactsofrockclimb-
facevegetationcommunity structure. Inaddition, Kuntz and Larson
onthecliffface.Therefore,as demanded by Holzschuh (2016), it is
necessary to consider these physicalfactors (e.g. microtopography)
&Hessl, 2015;Kuntz& Larson,2006a);however,moststudies have
neglected this keyaspect. Furthermore, it is also likely that species
withdifferinglifeformswill responddifferentlyto cliffstructureand
ecosystems,byofferingvaluable guidance forpracticalconservation
Thegeneral aim ofthisstudy istodeterminetheeffects ofrock
climbing on cliff plant communities, while considering microtopo-
implementedinthesehabitats.Forthispurpose,wefirst analysethe
Chulilla(Spain), a highbiodiversityarea oftheMediterraneanregion
FIGURE1 StudyarealocatedinChulilla,Levantecoast(Spain),wherewesampledninerockclimbingroutesincludedinfoursectors
Applied Vegetation Science MARCH- SALAS et AL.
2.1 | Study site
We surveyed in situ cliff formations along the village of Chulilla,
Valencia, in the southwest Iberian system mountains of Spain
stones from the Superior and Middle Jurassic periods (Santisteban,
2012).Thedominantvegetation communityonthe cliffsisaJasonio
glutinosae–Teucrietum thymifolii association (Agulló, Alonso, Juan,
enneaphylla(L.)DC.andTeucrium thymifoliumSchreb.
Rockclimbingactivityin Chulilla started inthe 1980s; in recent
routes are used forsport rock climbing, which requires drilling into
2.2 | Field survey design and data collection
Nine rock-climbing routes, distributed along four outcrops (hence-
and‘Fantasía’(see Figure1 map, Table S1). Field surveys were con-
rangingfromeastto southwest (and delineated them with standard
cardinal and intercardinal directions) to optimize biodiversity cap-
ture.Asanindirectmeasureof rockclimbingintensity,weidentified
beginner, intermediate and experienced level rock climbing routes
(5.4–5.11 on the rock climbing difficulty scale; Table S1), assuming
areas,wedesigned acase-controlsurveywith3m×3m quadrats,
each composed of three1m×3m transects (i.e. plots): a central
transectalongacommonlyused climbingroute(i.e. climbedtran-
unclimbedtransects) used as controlpoints.Theproximityofthe
ences between climbed and unclimbed transects.To examine the
climbing route: top, middle and bottom (Figure2). The bottom
quadratwasestablished 1–2mabovetheground,withthemiddle
andtop quadrats placed above at proportionaldistancesso as to
span the cliff height. Forclimbing route denoted ‘a1’ it was only
including 50 unclimbed and 25 climbed.
We identified all species in each transect using Castroviejo
(1986–2012) and measured their respective percentage cover. To
assessvegetationcoverforeachspecies,we measuredandsummed
thesquareareaofallindividuals ofa species, and used thattocal-
culate the proportion of the total transect area (3m2) covered by
thatspecies. FollowingtheMülleretal.(2004)classificationand the
cialized rock-dwelling species:allspecieswithstrictassociationtorocky
habitats;(M)moderately associated to rocky habitats species:speciesas-
sociated with other habitats but able to live recurrently in rocky habi-
tats;and(G)generalist species:ubiquitousspecieswithnoassociation
Physical variables of each rock-climbing route (i.e. cliff height,
aspect and average slope)were also recorded. Total surface ofthe
FIGURE2 Sampledesign.Wesampledthreequadrats(3m×3m)
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2.3 | Statistical analysis
We used the Shapiro-Wilk normality test and Bartlett test for ho-
mogeneityofvariancesto checknormalityand homoscedasticityfor
speciesrichness and percentage plantcover.Allvariableswere nor-
mal except M species richness and vegetation cover. We applied a
^0.7transformationtoMrockyhabitat species richness and a ^0.2
Using the lme4package(Bates,Mächler,Bolker,&Walker,2015)
bined effects of rock climbing impact and microtopographic condi-
simplify analyses and avoidover-fitting, we first performed individ-
eachmicrotopographicvariable. Since the percentageof cracks was
alonewasincludedinthesubsequent LMMsassessing rockclimbing
impacts.Inthese LMMs, percentageofcracks,quadratposition(i.e.
bottom,middle and top), rockclimbingtransects(i.e.climbedorun-
ingroutenested within sector was used as random factor.Forboth
speciesrichness andcover,wetested ourthreespeciesgroupsboth
usingstep-wise backward elimination. Furthermore,we constructed
ficultyoftherouteanditsaspect.Weexaminedthe main effectsof
allthe models usingChi-square tests. When main effects were sig-
nificantin factorscontainingmorethantwolevels,weapplied post-
We recorded a total of 34 vascular plant species (Table S2). All of
themhaveaMediterraneannativedistribution,exceptCeterach offici-
narumWilld.andOpuntia maxima Mill.,whichare originallyfromthe
Holarctic and Neartic, respectively. Among the Mediterranean spe-
rest(i.e. 70.59%)werenon-specialistrockspecies. Withinthelatter,
andca.75% were generalist species (Table S2).Meanplantspecies
richness on the 75 cliff-face transects was 2.68±0.18 species/m2
3.1 | Physical condition effects
Overallspecies richnessrosesignificantly(
=7.38,p = .007) asthe
=0.87,p = .351).However,
TABLE1 ResultsofLMMtestingtheeffectsofquadrat(i.e.top,middle,bottom),climbingeffect(i.e.climbed,unclimbed)andpercentageof
Species Factor
Species richness Vegetation cover
df χ2p- value Sig. R2 (%) df χ2p- value Sig. R2 (%)
Overallsp. Quadrat 2 10.76 .005 ** 29.80 2 10.80 .006 ** 12.04
Climbingeffect 1 2.17 .140 1 3.67 .055
%cracks 1 7.38 .007 ** 1 0.87 .351
Specializedspp. Quadrat 2 1.52 .469 16.82 2 0.07 .967 6.65
Climbingeffect 10.04 .843 1 0.08 .773
%cracks 10.40 .517 1 1.96 .161
Quadrat 2 16.78 <.001 *** 34.93 2 20.00 <.001 *** 25.85
Climbingeffect 14.08 .043 * 1 2.30 .130
%cracks 1 18.76 <.001 *** 1 6.77 .009 **
Quadrat 2 6.79 .033 * 11.65 2 9.08 .011 * 15.46
Climbingeffect 1 0.38 .538 1 0.06 .812
%ofcracks 1 1.92 .166 1 0.48 .490
Quadrat 2 12.82 .002 ** 45.61 2 18.98 <.001 *** 29.40
Climbingeffect 14.12 .042 * 1 3.96 .047 *
%cracks 120.43 <.001 *** 1 3.92 .003 **
≤1.66,p .20),thereforetheseresultswerenotincludedinthetable.Marginal
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byexaminingeachspecies groupseparately,wefounda positiveef-
fectof the percentage ofcracksforgeneralists(Table1).There was
no effect of crack percentage on specialized rock species richness
=0.40,p = .517)orvegetationcover(
=1.96,p = .16).Similarly,
speciesmoderatelyassociatedwith rocky habitat were not affected
bycrackpercentage.However,therichnessofnon-specialized spe-
cies increased as the percentage of cracks increased (
p < .001),asdidtheircover(
=6.77,p = .009;Table1).
Plants were distributed differently along the cliff face in terms
of both species richness (
=10.76, p = .005) and vegetationcover
=10.80, p = .006; Figure3). Average richness and cover of vas-
cularplantswassignificantlylowerin bottomquadrats(species rich-
ness=2.04±0.29, vegetation cover=0.53±0.16%) than in the
middle (3.04±0.30, 1.92±0.72%) and top quadrats (3.04±0.28,
2.02±0.70%). Again, the effect differed between rock-specialized
and non-rock-specialized species (Figure3). While both richness
=1.52, p = .469) and cover(
= 0.07, p = .967) of rock specialist
speciesdid not differ across the differentquadrats ofthe cliff face,
non-specializedrockspeciesrichness (Figure4;
=16.78,p < .001)
=20.00,p < .001) weresignificantlyhigherin
Finally,we did not find significant influenceof the average slope of
3.2 | Rock climbing effect
Wedid not find evidence thatrock-climbing activity affectedover-
=2.17,p = .140)andonlyamarginaleffecton
=3.67,p = .055)inouranalysesacrossallspecies
sampled.However,weagainfoundthattherockclimbingeffect dif-
feredbetweenspeciesgroups. Rock-climbing activity didnotaffect
=0.04,p = .843;cover
p = .773) but non-specialist species richness was significantly lower
=4.08,p = .043;covernotsignificant:
=2.30,p = .130).Amongnon-specialists,generalistspeciesrichness
=4.12,p = .042),
specialistspecies were notsignificantlyaffected(
=0.38,p = .538;
Figure5).The samepatternwasfound invegetationcover(general-
=3.96,p = .047; moderate rockspecialist,
=0.06,p = .812;
≤1.66,p .20).
Althoughcliff environmentecosystemsare consideredrelativelyun-
affectedby humans overthelastcenturies, increasing rockclimbing
activity is altering vegetation present in this habitat (e.g. Adams &
2003;Thiel & Spribille, 2007).Our results support theexistence of
negativeeffectsofrock climbingpressuresoncliffvegetation. More
where rock climbing negatively impacted species diversity and af-
fectedspeciescomposition(Figure S1;TableS4).However,contrary
FIGURE3 Left:Speciesrichnessperquadrat;Right:Covertureof
Vegetation cover (%
Quadrat height
Middle Top
Species richness
Quadrat height
Middle Top FIGURE4 Top:Cliffheight(i.e.quadrat)effectonspecies
Applied Vegetation Science
to Müller etal. (2004), we found these effects were mostly limited
togeneralistspecies, whilerockspecialistspecieswerenotaffected.
previously been implemented in these environments. Furthermore,
The higher tolerance capacities of rock specialist plants to
rootssystemscan find anchorage (Matthes-Sears& Larson, 1995).
This could help them to resist and withstand rock-climbing distur-
Grammatikopoulos,2007).Although the majorityofthese traits are
found.Forinstance,S. enneaphyllausesantsas pollinatorsand seed
provide advantages to rock specialist plants, potentially affording
someplants present along the rock-climbingroute.Thiscan reduce
the substrate presentwithin these cracks, and alter the seed bank.
ciespresentthat requirea richer substratewith more resources for
establishment. Our results confirmedthe importance of microtopo-
mentwithotherstudies(DoCarmo &Jacobi,2016;Kuntz&Larson,
2005, 2006a,b; Lundholm & Larson, 2003). While specialized rock
specieswereable tosurvivewithout ahighnumberofcracks,non-
bance.Inthe bottompart ofthecliff,generalistspecies richnessand
vegetation cover were similar in the climbed and unclimbed transects.
Nevertheless,therecould be multiple reasonsforthis result. When
climbersstart to ascend a rockclimbingroute,theyusuallyevaluate
withoutropesorharnesses).Bothactivities can result inthefurther
thereducedpresence of species at the bottom of a cliff face;while
specialized rock species have some traits and defence systems to
may be more vulnerable.
Ourfindings showedthatthe degree ofspecies dependence on
ingpressures.Species with less specializationtocliffconditions(i.e.
havenon-specializedrockspecies (>70%ofspeciesfound),in accor-
dancewith Mülleretal. (2004).Therefore,theloss ofthese species
willdrasticallyreducespecies diversityinthesesingular ecosystems,
as well as change the composition and structureof the plant com-
researchon cliffs, andparticularlyareaswith rockclimbingactivity.
Inourcase-controldesign, we examined the impacts of rockclimb-
ing using a spatial approach, but also provided a starting pointfor
FIGURE5 Top:Rockclimbingeffectonspeciesrichnessoneach
Applied Vegetation Science MARCH- SALAS et AL.
monitoringseries,which might allowstudyofthe long-term effects
peatingthe surveyinsituonlyrequiresa detaileddescriptionofthe
placementof surveyunitsalongeachrock-climbingroute.As far as
special attention must be paid to the placement ofthe in situ sur-
veytransectsin orderto optimizethecontrolfunctionofthelateral
the potential ofthe analysis. This would calls for higher separation
cannot be considered completelyundisturbed. In addition, we also
Inconclusion,despite the strong influence of physical and envi-
importantdeterminantincliff-facefloralstructure,since italtersthe
thatfuturemanagementandconservationplansand studiesaccount
not only forendemic species, which are often more protected, but
surveydesignbasedon ourproposal,wouldhelpeffortstopreserve
We thank the Polytechnic University of Valencia and Botanical
thesurveymethodsand experimentaldesign,aswelltheir latersug-
MMS and MMM designed the study. MMM designed the survey
methodology and implemented the study, collecting all the data.
thefirst draftofthemanuscript. MMS, MMM,GP,PTI,EH andLRP
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stone outcrops used for rock climbing in thevicinity of Göttingen
Vogler, F., & Reisch, C. (2011). Genetic variation on the rocks –
the impact of climbing on the population ecology of a typical
cliff plant. Journal of Applied Ecology, 48, 899–905. https://doi.
Additional Supporting Information may be found online in the
Figure S1Percentagevegetationcoverofunclimbedandclimbedtran-
sects with specialized rock species, moderatelyassociated to rocky
Table S1Differentrockclimbingroutessampled,with somephysical
weincluded latitude and longitude. Fornumeric difficulties weused
theYosemiteDecimalSystem(YDS) fromtheUSA,andalso catego-
Table S2Speciesfoundindifferentsampledcliffs.Wedividedspeciesby
izedrockspp. (S),moderatelyassociatedto rockyhabitatsspp.(M) and
Table S3Results of LMM testing the effects of: slope, cliff height,
Table S4Presence(i.e.numberofindividualsperspecies)andvegetation
How to cite this article:March-SalasM,Moreno-MoyaM,
to rock climbing activity. Appl Veg Sci. 2018;00:1–9.
... Seventeen of 19 studies surveyed the impact on vascular plants, while only 13 included lichens and bryophytes (Table 1). Study areas covered cliffs in Europe (Müller et al., 2004;Rusterholz et al., 2004;Baur et al., 2017;Lorite et al., 2017;March-Salas et al., 2018;Schmera et al., 2018) and North America (Nuzzo, 1996;Camp & Knight, 1998;Farris, 1998;McMillan & Larson, 2002;Walker et al., 2004;Kuntz & Larson, 2006;Adams & Zaniewski, 2012;Clark & Hessl, 2015;Tessler & Clark, 2016;Boggess et al., 2017;Covy et al., 2019;Reding, 2019;Harrison, 2020). Substrate -bedrock -was limited to sandstone, limestone, marl, granite, quartzite, basalt, shale, conglomerate and dolomite. ...
... Seventeen of 19 studies surveyed the impact on vascular plants, while only 13 included lichens and bryophytes (Table 1). Study areas covered cliffs in Europe (Müller et al., 2004;Rusterholz et al., 2004;Baur et al., 2017;Lorite et al., 2017;March-Salas et al., 2018;Schmera et al., 2018) and North America (Nuzzo, 1996;Camp & Knight, 1998;Farris, 1998;McMillan & Larson, 2002;Walker et al., 2004;Kuntz & Larson, 2006;Adams & Zaniewski, 2012;Clark & Hessl, 2015;Tessler & Clark, 2016;Boggess et al., 2017;Covy et al., 2019;Reding, 2019;Harrison, 2020). Substrate -bedrock -was limited to sandstone, limestone, marl, granite, quartzite, basalt, shale, conglomerate and dolomite. ...
... We found considerable variation in selection and comparison of climbed to | 3 of 12 Applied Vegetation Science BOGGESS Et al. unclimbed transects across the studies. Five studies used paired transects in which unclimbed transects were placed adjacent to climbed routes with similar slope and aspect (Walker et al., 2004;Clark & Hessl, 2015;Tessler & Clark, 2016;Boggess et al., 2017;Lorite et al., 2017). The remaining 14 studies did not pair transects, presumably due to limited availability of unclimbed transects (Table 2) ...
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Questions Cliff vegetation is diverse, understudied, and threatened by increased human disturbance. The growing popularity of rock climbing heightens the need for science‐based management to balance recreational use and conservation of cliff ecosystems. What has existing research revealed about the impact of climbing on vegetation? Are the conclusions consistent across the literature? If not, how can research methods be streamlined and standardized to produce more consistent results and reliable conclusions? Methods We present a review of vegetation‐focused climbing impact studies written in English. We compare study design and climbing‐specific considerations in nineteen studies and report the impact of rock climbing on richness and abundance of lichens, bryophytes, and vascular plants. We then propose a set of best‐practices to guide design of future studies. Results Our work reveals that existing studies have employed widely differing methods for data collection and analysis. The effects of climbing on vegetation also varied among studies. Standardizing methods, such as pairing climbed and unclimbed transects or including a metric for climbing use, will generate more reliable and useful conclusions about the effect of climbing on vegetation. Conclusions Climbing will increasingly disturb cliff ecosystems. Our proposed best‐practices for climbing study methods are one way to produce more accurate information to inform climbing management plans, ultimately enhancing cliff conservation.
... Thus, rock-climbing poses a potential threat, not only for the diversity of cliff vegetation but also for unique and threatened plant species (Larson et al., 2000). However, only a few local small-scale field studies exist on the effect of rockclimbing on cliff plant species (e.g., Clark and Hessl, 2015;Lorite et al., 2017;March-Salas et al., 2018;Schmera et al., 2018;Strumia et al., 2020), and these have not always been properly conducted (Holzschuh, 2016). Moreover, these isolated case studies did not state the criteria used to select study sites, leading to an unknown relevance of the sites for conservation purposes. ...
... The assessment of the effect of rock-climbing on cliff plant species is especially relevant for Mediterranean cliffs (Lorite et al., 2017;March-Salas et al., 2018). The Mediterranean biome is a plant biodiversity hotspot (Myers et al., 2000;Médail and Diadema, 2009), harboring a large amount of endangered and endemic cliff plant species (Larson et al., 2000). ...
... These outdoor climbing locations (sometimes strikingly called sports facilities) ease access and engage increasingly higher numbers of participants (USDA, 2012) that, in turn, need more climbing locations in nature. Sport climbers repeatedly use the same stretches of the cliff face, which poses an evident threat to plant species (March-Salas et al., 2018). This is especially true in Spain, where the climate allows rock-climbing during most of the year and rock cliffs are spread around the country, not only in isolated mountain ranges (Myers et al., 2000;Di Castri and Mooney, 2012). ...
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In recent years, the popularity of rock-climbing has grown tremendously, setting an increasing pressure on cliff habitats. Climbing may be particularly harmful in the Mediterranean biome due to its appropriate environmental conditions for climbing. A few studies have identified the effect of climbing on plant diversity at a small-scale (namely locally or even just in specific climbing areas). However, no studies exist assessing the potential risk of rock-climbing on a broad-scale (e.g., regional or national). The study aims to identify the priority locations and priority cliff plant species in Spain to focus future study efforts. Spain was selected because it is a plant biodiversity hotspot, with a great diversity of endemic and endangered species, and one of the most popular destinations for climbers. We used a geographic information system-based approach to model the spatial concurrence among Spanish climbing areas (and climbing intensity), natural protected areas (NPAs), and distribution of threatened cliff plants (and their IUCN threat category). We found that 53.5% of climbing areas in Spain are located within a NPA, most of them falling into NPAs of medium protection level. We mapped 151 threatened cliff plants, identifying four medium priority Mediterranean locations and eight priority species in which future research efforts should be focused. High-priority study locations are absent in Spain according to our spatial modeling. For the first time on a national scale, this study identifies areas in which climbing represents a potential threat for cliff habitats and threatened plants. These findings contribute to designing field studies on the effects of rock-climbing on Mediterranean cliffs, laying the groundwork for a sustainable, yet challenging, balance between the protection of these unique habitats and rock-climbing.
... Thus, rock-climbing poses a potential threat, not only for the diversity of cliff vegetation but also for unique and threatened plant species (Larson et al., 2000). However, only a few local small-scale field studies exist on the effect of rockclimbing on cliff plant species (e.g., Clark and Hessl, 2015;Lorite et al., 2017;March-Salas et al., 2018;Schmera et al., 2018;Strumia et al., 2020), and these have not always been properly conducted (Holzschuh, 2016). Moreover, these isolated case studies did not state the criteria used to select study sites, leading to an unknown relevance of the sites for conservation purposes. ...
... The assessment of the effect of rock-climbing on cliff plant species is especially relevant for Mediterranean cliffs (Lorite et al., 2017;March-Salas et al., 2018). The Mediterranean biome is a plant biodiversity hotspot (Myers et al., 2000;Médail and Diadema, 2009), harboring a large amount of endangered and endemic cliff plant species (Larson et al., 2000). ...
... These outdoor climbing locations (sometimes strikingly called sports facilities) ease access and engage increasingly higher numbers of participants (USDA, 2012) that, in turn, need more climbing locations in nature. Sport climbers repeatedly use the same stretches of the cliff face, which poses an evident threat to plant species (March-Salas et al., 2018). This is especially true in Spain, where the climate allows rock-climbing during most of the year and rock cliffs are spread around the country, not only in isolated mountain ranges (Myers et al., 2000;Di Castri and Mooney, 2012). ...
Full-text available
In recent years, the popularity of rock-climbing has grown tremendously, setting an increasing pressure on cliff habitats. Climbing may be particularly harmful in the Mediterranean biome due to its appropriate environmental conditions for climbing. A few studies have identified the effect of climbing on plant diversity at a small-scale (namely locally or even just in specific climbing areas). However, no studies exist assessing the potential risk of rock-climbing on a broad-scale (e.g., regional or national). The study aims to identify the priority locations and priority cliff plant species in Spain to focus future study efforts. Spain was selected because it is a plant biodiversity hotspot, with a great diversity of endemic and endangered species, and one of the most popular destinations for climbers. We used a geographic information system-based approach to model the spatial concurrence among Spanish climbing areas (and climbing intensity), natural protected areas (NPAs), and distribution of threatened cliff plants (and their IUCN threat category). We found that 53.5% of climbing areas in Spain are located within a NPA, most of them falling into NPAs of medium protection level. We mapped 151 threatened cliff plants, identifying four medium priority Mediterranean locations and eight priority species in which future research efforts should be focused. High-priority study locations are absent in Spain according to our spatial modeling. For the first time on a national scale, this study identifies areas in which climbing represents a potential threat for cliff habitats and threatened plants. These findings contribute to designing field studies on the effects of rock-climbing on Mediterranean cliffs, laying the groundwork for a sustainable, yet challenging, balance between the protection of these unique habitats and rock-climbing.
... Limestone cliffs are globally a rare habitat supporting highly specialized and distinct biotas including lichens, bryophytes, vascular plants, insects and gastropods (Larson et al., 2000;Schilthuizen et al., 2003). The high species richness, large number of rare species and rarity of the habitat type give limestone cliffs a high conservation value (Wassmer, 1998;Baur, 2003;Ursenbacher et al., 2010). ...
... The repeated removal of plants and soil from crevices prevents a re-colonization. March-Sala et al. (2018) also reported a climbing-related reduction in plant species richness, which was mainly a result of a decrease in generalist but not specialist species on climbing routes. Various possibilities should be considered when interpreting contrasting findings. ...
... Limestone cliffs provide a variety of microhabitats for snails, including xerothermic vegetation at the cliff edge and on ledges, accumulated rock and debris partly covered with vascular plants, bryophytes and decaying leaf litter at the talus and in fissures, pockets and shallow crevices in the rock face, and unstructured rock surface (Larson et al., 2000). Most snail species exhibit particular habitat requirements and thus occur only in certain microhabitats on rocky cliffs. ...
Limestone cliffs in the Jura Mountains harbour species-rich plant and animal communities including rare species. Sport climbing has recently increased in popularity in this habitat and several studies have reported damage to cliff biodiversity. However, so far how damage levels vary with climbing intensity has not been investigated. We evaluated the effects of climbing intensity on the diversity of vascular plants and land snails in 35 limestone cliff sectors in the Northern Swiss Jura Mountains. Mixed-effects models were used to examine whether species richness of plants and land snails differ between cliff sectors with low and high climbing intensity and unclimbed cliff sectors (controls) taking into account potential influences of cliff characteristics (aspect, cliff height, rock microtopography). At the cliff base, the best fit model revealed that plant species richness was affected by climbing intensity and cliff aspect. Plant species richness was reduced by 12.2% and 13.1%, respectively, in cliff sectors with low and high climbing intensity compared to unclimbed cliff sectors. On the cliff face, plant species richness was only influenced by climbing intensity (species richness reduction by 24.3% and 28.1%). Combining data from cliff base, face and plateau, the best fit model revealed that land snail species richness was only affected by climbing intensity (species richness reduction by 2.0% and 13.7%). In both organism groups, species composition was increasingly altered by increasing climbing intensity. Our study provides evidence that even low climbing intensity reduces cliff biodiversity and that damage becomes more pronounced with increasing climbing intensity.
... Nevertheless, recent studies accounting for this methodological drawback still found negative effects of climbing activities on rock vegetation (March-Salas et al., 2018;Tessler & Clark, 2016) and showed that increasing climbing intensity goes along with increasing alterations of species communities on rocks (Lorite et al., 2017;Schmera, Rusterholz, Baur, & Baur, 2018). While for rock-nesting bird species, simple human presence leads to disturbance (Camp & Knight, 1998;Covy, Benedict, & Keeley, 2019), negative effects of rock climbing on sessile rock-dwelling organisms are mainly attributed to mechanical disturbances such as trampling and removal of soil and vegetation (Holzschuh, 2016). ...
... In the results of the diverse studies that documented impacts of climbing on rock vegetation (Lorite et al., 2017;March-Salas et al., 2018;Müller et al., 2004;Nuzzo, 1996;Rusterholz et al., 2004;Schmera et al., 2018;Tessler & Clark, 2016), the potential chemical impact due to climbing chalk and the mechanical impacts of climbing such as trampling and removal of soil and vegetation are usually confounded on climbed rocks (Holzschuh, 2016). In contrast, our study assessed the distribution of climbing chalk separately from its impact on species in an experiment, but the real impact of climbing chalk on rock-dwelling plants under natural conditions is difficult to deduce. ...
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Rock climbing is popular, and the number of climbers rises worldwide. Numerous studies on the impact of climbing on rock‐dwelling plants have reported negative effects, which were mainly attributed to mechanical disturbances such as trampling and removal of soil and vegetation. However, climbers also use climbing chalk (magnesium carbonate hydroxide) whose potential chemical effects on rock‐dwelling species have not been assessed so far. Climbing chalk is expected to alter the pH and nutrient conditions on rocks, which may affect rock‐dwelling organisms. We elucidated two fundamental aspects of climbing chalk. (a) Its distribution along nonoverhanging climbing routes was measured on regularly spaced raster points on gneiss boulders used for bouldering (ropeless climbing at low height). These measurements revealed elevated climbing chalk levels even on 65% of sampling points without any visual traces of climbing chalk. (b) The impact of climbing chalk on rock‐dwelling plants was assessed with four fern and four moss species in an experimental setup in a climate chamber. The experiment showed significant negative, though varied effects of elevated climbing chalk concentrations on the germination and survival of both ferns and mosses. The study thus suggests that along climbing routes, elevated climbing chalk concentration can occur even were no chalk traces are visible and that climbing chalk can have negative impacts on rock‐dwelling organisms.
... Few other Valeriana species are able to grow abundantly in damp rock-cliffs at this high altitude, directly rooted in fissures or small soil pockets (e.g., V. chilensis Borsini in Chile or V. ruizlealii Borsini in Argentina). Rock-cliffs are challenging habitats with high erosion rates, limited soil depth and nutrients availability (Mathaux 2017;March-Salas et al. 2018). Mountain microclimatic conditions at high elevations are also severe due to high insolation and extreme low temperatures (Gale 1972). ...
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The species Valeriana praecipitis (Caprifoliaceae), new to science and endemic to the Ñuble Region, Central Chile, is formally described. Morphological data support its placement in a new species, clearly different from V. philippiana. A detailed description, insights about its habitat and ecology, distribution map and illustration are provided. A table of comparison is also given with the morphological characters discriminating V. praecipitis from V. philippiana. The species is assessed as Endangered (EN) under the IUCN categories.
... Climbing activities affect cliff site species [1][2][3][4][5]. With bouldering, rock climbing and other climbing activities becoming more popular, and with sport climbing being now accepted as an Olympic discipline, the importance of understanding the ecological impact of climbing activities increases. ...
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Climbing activities affect cliff site species. With cliff sites harbouring unique species communities, the rise in popularity of outdoor climbing activities is a major threat. In this study, we assessed a previously unclimbed boulder before, during and after 500 climbing ascents. We observed an overall reduction in lichen cover by 4.2–9.5%, located around the footholds and combined foot- and handhold but not the handhold. We found the reduction in lichen cover to be strongest at the very start of the climbing treatment and to lessen over time. Therefore, management should focus on directing climbing activities to selected sites, while protecting sites with high conservation value where climbing is prohibited entirely.
... In such conditions, conventional field sampling at the community level (e.g., permanent plots or transects), assuming the presence of the data collector close to rocky face, is challenging for safety reasons; moreover, the engagement of personnel with good expertise in climbing and rappelling techniques is required [4,[16][17][18][19][20][21][22][23]. The use of climbing routes causes also a clear bias in the sampling design, due to the particular features (unbroken and dry faces with few or no crevices) needed to have feasible routes that could be not representative of the average conditions and vegetation cover of all the cliff [18,20,23]. ...
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Cliffs are reservoirs of biodiversity; therefore, many plant species and communities of inland and coastal cliffs are protected by Council Directive 92/43/EEC (European Economic Community), and their monitoring is mandatory in European Union countries. Surveying plants on coastal cliff by traditional methods is challenging and alternatives are needed. We tested the use of a small Unmanned Aerial Vehicle (UAV) as an alternative survey tool, gathering aerial images of cliffs at Palinuro Cape (Southern Italy). Four photo-interpreters analysed independently the derived orthomosaic and plotted data needed for the monitoring activity. Data showed to be not affected by photo-interpreters and reliable for the prescribed monitoring in the European Union (EU). Using the GIS analysis tools, we were able to: (a) recognise and map the plant species, (b) derive and measure the area of distribution on the cliff of habitat and species, and (c) count Eokochia saxicola individuals and gather quantitative data on their projected area. Quality of the images represented the main constraint, but incoming technological improvements of sensors and UAVs may overcome this problem. Overall results support the use of UAVs as an affordable and fast survey technique that can rapidly increase the number of studies on cliff habitats and improve ecological knowledge on their plant species and communities.
... The high diversity of the coastal garrigue can be attributed to the harsh environmental conditions with barren soil, wind, high solar radiation and seawater spray. These factors determine a spatial variability resulting in a mosaic of microhabitats enabling the co-occurrence of various stresstolerant specialist and certain generalist plant species (March-Salas et al. 2018), thus, increasing species richness (Van der Maarel 2003). Correspondingly, the highest number of endemic plants was found here, which are often stress-tolerant taxa that have adapted to harsh coastal and saline habitats (M edail and Qu ezel 1999). ...
Islands crucially contribute to the Mediterranean Basin’s high floristic diversity, which, however, is at risk facing climate and land-use changes. Besides the identification of highly diverse areas, the knowledge about factors favouring diversity is of great importance. We analysed plant species diversity and composition related to environmental factors over varied vegetation units on a former Italian prison island in the northwest of Sardinia. Due to a long history of land use with grazing and later abandonment the nowadays protected island features a semi-natural landscape and can serve as an example for strongly anthropogenic altered insular ecosystems. Floristic composition, soil properties, microclimate and ungulate abundance were assessed. Relationships of vegetation composition and diversity with abiotic variables were examined by Canonical Correspondence Analysis, which indicated the importance of air temperature, soil moisture, slope gradient and C/N ratio for floristic differentiation. Most important abiotic factors for plant species richness were relative air humidity and soil moisture, while floristic diversity was mainly determined by air temperature and pH. Furthermore, observation data pointed to an adverse influence of ungulate abundance for plant species diversity. Regarding nature conservation, grazing intensity thus must be critically taken into account, especially for sensitive vegetation units like the coastal garrigue.
Conference Paper
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Rock climbing continues to increase in popularity, but it is difficult to generalize about the positive and negative impacts climbing has on vegetation communities, including lichens. Vertical rock faces are preferred habitat for many lichen and plant species, but it is unclear what kind if threat climbing poses to these communities. As part of a longer, empirical study of the effects of climbing on lichen communities, we used text analysis of the existing literature on this topic to better understand trends in research approaches and findings to date. Based on the patterns that emerged from our text analysis, we make recommendations as to what types of research efforts might be most valuable in furthering our understanding of the effects of rock climbing on cliff communities.
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Rock climbing is among the outdoor activities that have undergone the highest growth since the second half of the 20th century. As a result, cliff habitats, historically one of the least disturbed by human colonization worldwide, are facing more intense human pressure than ever before. However, there is little data on the impact of this activity in plant-communities, and such information is indispensable for adequate manager decision-making. The goal of this study was to determine the impact of rock climbing on plant communities in terms of cover, richness, and composition in relation to climbing intensity on typical Mediterranean limestone cliffs. Three rock-climbing sites were selected in the Baetic range (SE Spain), corresponding to qualitative categories of climbing frequentation: i)“low” (low frequentation with intermittent climbing), ii)“medium” (high frequentation without overcrowding), and iii) “high” (high frequentation with overcrowding). Within each site, we selected climbing routes and adjacent areas free of climbing, then we carried out a photoplot-based sampling by rappelling. We analysed the images to calculate: richness, species cover, and total cover. This study shows that rock climbing negatively affected the cliff plant community at all three study sites. A significant decrease in plant cover, species richness and a shift in the community composition were recorded for climbed areas, the cover being the variable most sensitive to rock climbing. Impact observed proved to be related to the frequentation level. Low-frequentation sites, with usually more specialized climbers, underwent relatively mild damages, whereas at high frequentation sites the impact was severe and the conservation of the species, especially rare ones, became jeopardized. Our study is the first one available to investigate climbing impact on plant communities in Mediterranean areas, but more research on the impact of rock climbing is needed to assess the regulation of this activity. Regarding management guidelines, we propose a management guideline protocol to evaluate climbing routes and design: i) “Sites free of climbing”, ii) “Strictly regulated climbing routes”, iii) “Mildly regulated climbing routes”, or iv) “Free climbing routes”. © 2017 Lorite et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Least-squares means are predictions from a linear model, or averages thereof. They are useful in the analysis of experimental data for summarizing the effects of factors, and for testing linear contrasts among predictions. The lsmeans package (Lenth 2016) provides a simple way of obtaining least-squares means and contrasts thereof. It supports many models fitted by R (R Core Team 2015) core packages (as well as a few key contributed ones) that fit linear or mixed models, and provides a simple way of extending it to cover more model classes.
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Aims We investigated how outcrops of different geological origins enhance the plant megadiversity of the Atlantic rainforest hotspot. Methods We collected vegetation, topographic, and soil fertility data from 50 2 m2 plots in each of nine rock outcrops (three ironstones -or cangas, three quartzites and three granitoids) in the Iron Quadrangle, SE Brazil. We examined the response of community diversity and structure patterns to edaphic and topographic gradients by means of diversity profiles, clustering and ordination analyses. Species were organized into nine functional groups. Results We inventoried 17,690 individuals belonging to 352 species. Functional groups with largest cover were sclerophytic shrubs (in cangas), graminoid and poikilohydric herbs (in both granitoids and quartzites). Granitoid plant communities were the least diverse, on account of fewer substrate types leading to more xeric conditions. The multivariate analyses sorted the outcrops by geological origin, although within-lithotype similarity was low. There was stronger similarity between cangas and quartzites, separated from granitoids. Soil was nutrient-poor, and variables most influencing this pattern were number of substrates, topographic heterogeneity, soil depth, and aluminum saturation. Conclusions Saxicolous plant communities responded more strongly to microtopographic than soil fertility parameters. Each lithotype contributes differently to the high alpha- and especially beta-diversity within the Atlantic Rainforest matrix.
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QuestionsTo what extent do fine-scale substrate variations affect the structure and diversity of rock outcrop vascular plant communities? How can we define the appropriate scale to measure fine-scale substrate heterogeneity in rocky systems?LocationNine rock outcrops in the Iron Quadrangle, a priority area for biodiversity conservation in southeast Brazil.Methods Geomorphology and rock mechanics methods were adapted to determine the appropriate scale to measure rock surface heterogeneity on granitoid, quartzitic and ironstone (canga) outcrops. Then, a roughness index was calculated from 60 microtopographic profiles in each lithotype to investigate the response of the plant community to this scale. The relation between surface heterogeneity and plant community richness, abundance, total plant cover and dominant species cover was quantified through linear regressions. A cluster analysis compared the percentage cover of functional groups in each outcrop, and diversity profiles were built based on Rényi's alpha. PERMANOVA was used to test for significant difference in the relative cover among the functional groups.ResultsThe roughness index, scaled at 1 cm, had the best power to diagnose the presence of vascular plants. High surface heterogeneity was caused by high frequency of fissures, cracks and rock fragments. Linear regression models indicated that the community parameters are strongly related to variations in surface roughness. The community patterns revealed by the cluster analysis and the diversity profiles matched those of the roughness analysis. Dominant functional groups differed strongly between ‘smooth’ and ‘coarse’ microtopography. Desiccation-tolerant species prevailed in smooth outcrops, while sclerophytes and graminoids were better represented in coarse outcrops.Conclusions The composition of plant functional groups was affected by rock microrelief, and roughness was a significant predictor of plant community parameters. Functional group proportions reflected different adaptive plant strategies to two main stressful bedrock features: water shortage and mechanical resistance to root growth.
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QuestionWhat are the effects of rock climbing on diversity, abundance and composition on cliff-face vegetation along environmental and use gradients typical of modern climbing?LocationNew River Gorge National River, WV, US.Methods We compared species richness, abundance and composition of vascular plants, bryophytes and lichens on 79 pre-established rock climbs and 32 unclimbed ‘control’ sites across potential climb-use intensity and cliff structure using linear models, residual analysis and NMDS ordination.ResultsDifferences in species richness and abundance associated with potential climb-use intensity and cliff structure were variable across taxonomic groups. Linear models indicated that cliff angle was the strongest explanatory variable of species richness and abundance for all three taxonomic groups. Once the effects of biophysical variables were modelled, analysis of the residuals indicated that potential climbing-use intensity had a small but negative effect on species richness and abundance of vascular plants (range 3–6%), no effect on bryophytes (0%) and a substantial effect on lichens (range 10–12%). Similarly, NMDS ordination indicated that cliff angle, canopy height and aspect were the primary drivers of species composition. We observed no change in community composition due to climbing.Conclusions Other studies have observed significant impacts of climbing on vegetation at the base of cliffs. Here, we observe that potential climbing-use intensity has some impact on species richness and abundance of vascular plants and more significant impacts on lichens, however cliff angle is a fundamental control on cliff vegetation. Because of the challenge in sampling steep and overhanging cliffs, we recommend that climbers be directly involved in the assessment, monitoring and management of cliff resources in order to ensure that the full range of biophysical conditions of cliff ecosystems are considered.
Rock climbing has increased in popularity over the past 20 years. Meanwhile, there have been increasing calls for restrictions on rock climbing due to concerns about the impact of climbing on cliff biodiversity. However, the biological impacts of rock climbing are still not well understood. Here, I review the existing literature to assess the impact of rock climbing on cliff biodiversity. The majority of published results may be confounded by systematic abiotic differences between climbed and unclimbed cliffs, and this lack of proper controls may lead to the overestimation of the negative effects of rock climbing on biodiversity. Evidence for the impact of rock climbing on biodiversity is inconclusive for most taxa. Studies on lichens and vascular plants have described evidence for negative, positive and no effects of rock climbing. Snail biodiversity was found to be negatively affected, while reliable evidence of the impacts of rock climbing on birds is still lacking. Bryophytes were generally unaffected by rock climbing. Further research is urgently needed, because the mixed results of the existing studies do not allow final conclusions how rock climbing affects the cliff biota. Future studies should select comparable controls for biodiversity comparison, widen the focus to further cliff-associated taxa, and investigate how climbing effects vary with climbing intensity. Such studies would facilitate the improved management of rock climbing areas that are rich in biodiversity and contain rare and threatened species.
Thousands of tourists visit certain Antarctic sites each year, generating a wide variety of environmental impacts. Scientific knowledge of human activities and their impacts can help in the effective design of management measures and impact mitigation. We present a case study from Barrientos Island in which a management measure was originally put in place with the goal of minimizing environmental impacts but resulted in new undesired impacts. Two alternative footpaths used by tourist groups were compared. Both affected extensive moss carpets that cover the middle part of the island and that are very vulnerable to trampling. The first path has been used by tourists and scientists since over a decade and is a marked route that is clearly visible. The second one was created more recently. Several physical and biological indicators were measured in order to assess the environmental conditions for both paths. Some physical variables related to human impact were lower for the first path (e.g. soil penetration resistance and secondary treads), while other biochemical and microbiological variables were higher for the second path (e.g. β-glucosidase and phosphatase activities, soil respiration). Moss communities located along the new path were also more diverse and sensitive to trampling. Soil biota (Collembola) was also more abundant and richer. These data indicate that the decision to adopt the second path did not lead to the reduction of environmental impacts as this path runs over a more vulnerable area with more outstanding biological features (e.g. microbiota activity, flora and soil fauna diversity). In addition, the adoption of a new route effectively doubles the human footprint on the island. We propose using only the original path that is less vulnerable to the impacts of trampling. Finally from this process, we identify several key issues that may be taken into account when carrying out impact assessment and environmental management decision-making in the Antarctic area.
Global change threatens ecosystems worldwide, and tropical systems with their high diversity and rapid development are of special concern. We can mitigate the impacts of change if we understand how tropical ecosystems respond to disturbance. For tropical forests and streams in Puerto Rico this book describes the impacts of, and recovery from, hurricanes, landslides, floods, droughts, and human disturbances in the Luquillo Mountains of Puerto Rico. These ecosystems recover quickly after natural disturbances, having been shaped over thousands of years by such events. Human disturbance, however, has longer-lasting impacts. Chapters reflect many years of experience in Puerto Rico and other tropical areas and cover the history of research in these mountains, a framework for understanding disturbance and response, the environmental setting, the disturbance regime, response to disturbance, biotic mechanisms of response, management implications, and future directions. The text provides a strong perspective on tropical ecosystem dynamics over multiple scales of time and space.
1. A preliminary account has been given of the major types of rock habitats found in the Mediterranean region, for convenience distinguishing pavement, sloping, vertical and overhanging rock, the ledge and the step-crevice. The main factors of saxatile habitats have been annotated. 2. The plant communities that occupy these habitats in Palestine have been outlined. Each habitat is found to be characterized by distinct communities, often of a relict nature. Whereas vertical and overhanging rock support species that are almost exclusively chasmophytic, the step-crevice is occupied by many species derived from neighbouring maquis communities. 3. The following aspects of Mediterranean cliff communities have been discussed: (a) Life forms and their distribution in different communities. The predominance of the Chamaephyte (especially suffruticose) has been stressed, and reasons given for believing the woody habit so characteristic of chasmophytes to be most frequently a derived character. Longevity will be favoured by natural selection. (b) The distribution of chasmophytes in different groups of flowering plants. Saxatilism is considered an advanced and specialized character favoured by natural selection. (c) Seed dispersal. With the exception of many step-crevice plants disseminated by birds, wind-dispersal--often depending only on the lightness of the seed--was found to be predominant. (d) Discontinuous distribution caused by climatic and topographical changes. (e) Cliff communities as biologically closed communities, generally representing physiographic and/or edaphic climaxes. (f) The development of a saxatile habit in species not normally saxatile. This was found to occur at the edge of a species' range and/or under adverse conditions. Species of vertical and overhanging rock are believed to have the longest saxatile history; they show little morphological variation in any one locality. (g) Relicts; their recognition and significance. (h) Cliffs as refugia. They offer a refuge from unfavourable climatic change, competition with hillside communities, and grazing. In connexion with (d) and (h), Quaternary climatic changes in Palestine have been discussed. Rock communities suggest that the Mediterranean climate is drier than it has been during recent times. 4. An attempt has been made to outline the general evolution of Mediterranean chasmophytes. Geographical isolation, often resulting from the climatic and topographical changes of the Quaternary, has in most cases been a prerequisite of speciation. Ecological isolation has probably played a subsidiary role. The rarity of endemic chasmophytes, including both young and old types, is explained by the concept of genetic homogeneity; their ecological amplitude is exceedingly narrow. Unfavourable conditions during a chasmophyte's development have resulted in a reduction in the biotype supply. Following biotype-depletion, genetic drift has played a considerable part in speciation, particularly in the later stages of differentiation when the population is much reduced in size. Chasmophytes are in general a blind alley in the scheme of evolution: though they may differentiate in situ, they can rarely give rise to successful new forms. Due to high specialization, chasmophytes can often maintain themselves for a considerable period. But for many extinction seems inevitable.