Research article

Effects of land ownership and landscape-level factors on rare-speciesrichness in natural areas of southern Ontario, Canada

J. Lovett-Doust1,*, M. Biernacki2, R. Page1, M. Chan1, R. Natgunarajah1 and G. Timis1

1Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada N9B 3P4; 2Departmentof Biology, University of Memphis, Memphis, TN, 38152-3540 USA; *Author for correspondence (e-mail:jld@uwindsor.ca)

Received 28 March 2002; accepted in revised form 6 May 2003

Key words: Biodiversity, Conservation, Habitat, Land ownership, Landscape-level effects, Land-use, Natural ar-eas, Rare species fragmentation

Abstract

Surprisingly few studies have considered the extent to which the nature of the ownership of land is associatedwith differences in biodiversity. We analysed ownership and other landscape-level effects on rare-species rich-ness for both globally- and regionally-rare biota �including birds, herpetofauna, butterflies, mammals, and plants�in 289 designated natural areas �NAs� in southern Ontario, Canada. Information about each NA � includingarea, number of plant communities, ownership status and details of species diversity were collected from pub-lished sources. Length of perimeter of NA, relative isolation, and an estimate of fragmentation were measuredusing image analysis and GIS techniques. NAs were in general relatively small, with mean area of 158 ha �me-dian 85 ha, range from 0.9 to 1278 ha� for private NAs; public NAs had mean area of 132 ha �median 16 ha,range from 0.1 to 1481 ha�. Mean number of plant communities was 4.6 �median 4, range 1- 13� at private NAsand 3.8 �median 3, range 1-16� at public NAs. Our results show that, of several landscape-level factors, area hadthe greatest effects on rare-species richness and other biotic indices. Effects of area were followed by effects ofplant community diversity, however this was itself significantly affected by area and the extent of perimeter ofthe NA. Both these factors were followed by effects of ownership of the NA and by effects of isolation of theNA �represented by minimum distance to nearest NA and by number of NAs in 10 km radius�. Other landscape-level factors did not appear to have overall significant effects. Variation in area accounted for 0.1% to 29% ofvariation in number of rare species, with lower values for globally-rare, than for regionally-rare taxa. For allbiotic groups, public ownership of NAs was associated with significantly greater rare-species richness comparedto private ownership, even after other factors such as area were controlled. For all globally-rare biota exceptbutterflies, area of NA had greater effects on rare-species richness than did ownership. Richness of regionally-rare birds was more affected by plant community diversity than by area of NA. Number of recorded plant com-munities accounted from 2.1% of variation in number of globally-rare plant species to as high as 31% of variationin regionally-rare butterflies. The diversity of plant communities was itself influenced by total site area �account-ing for 45% of variation�, extent of elongation of the NA, and both external- and interior- edge perimeters. Pub-lic NAs had greatest numbers of rare biota and so should be a significant focus for conservation programs.Smaller, privately-owned patches of natural area dominate �by number and area� in this densely populated regionand their significance should not be overlooked.

© 2003 Kluwer Academic Publishers. Printed in the Netherlands.621Landscape Ecology 18: 621–633, 2003.

Introduction

Land-use change and ecosystem exploitation havebeen the primary forces causing loss of biological di-versity �Daily 1997; Vitousek et al. 1997; Sala et al.2000�. Land ownership patterns are obviously linkedto landscape alteration for agricultural, industrial andresidential needs, yet few studies have considered theextent to which the nature of the ownership of theland is associated with differences in biodiversity �butsee Kindscher and Scott, 1997; Crow et al. 1999;Lovett-Doust and Kuntz 2001�. In southern Ontario,a majority of the land exists under private ownership.Much of this is used agriculturally, leaving tracts offragmented natural areas also present �Pearce, 1993�.In the United States too, private land ownershipdominates – nearly 67% of land in the contiguousU.S. is privately held, another 2% is owned by stateor local governments, and the federal governmentowns 263 million ha, or 31% �Dale et al. 2000;Groves et al. 2000�. Developed, non-federal landsthere have increased by 18% in the past decade, to 92million ha or 4.4% of the total area �Dale et al. 2000�.In Ontario, projected population growth by 34% �toc. 16.6 million� by 2028 will further increase pressureon remaining natural areas �Government of Ontario,2000�. Privately-owned lands, both globally and insouthern Ontario, have been under more intensiveeconomic pressure than public lands in satisfying hu-man needs for goods and services �Pearce 1993; Ri-ley et al. 1996; Daily 1997; Vitousek et al. 1997�.Thus effects of land ownership on biodiversity in re-maining natural areas need to be considered in con-servation programs.

The extent of biodiversity maintained on privateversus public lands seems likely to be influenced byfactors directly associated with the purpose of theland ownership �Lovett-Doust and Kuntz 2001�. Itcould also be affected by factors indirectly related toownership, such as the landscape characteristics ofprivate versus public lands. For example, if publiclands tend to be found in larger and less fragmentedhabitat blocks, they could be expected to containmore biodiversity even if the selection of lands, ortheir management by private or public entities, wasidentical �see Groves et al. 2000�. MacArthur andWilson �1967� used area as a single, major factor,predicting species richness on oceanic islands. Thewell-known species-area relationship is overwhelm-ingly important in terrestrial ecosystems, howeverpatches may also be affected by other, landscape-level

factors in addition to size, such as the number oflandforms present and the extent of interior foresthabitat �Lovett-Doust and Kuntz, 2001�. Patterns ofbiotic diversity at public versus private lands has ob-vious pertinence to conservation and public planning,because of both the direct and indirect effects noted.

Here we investigate patterns of rare and threatenedbiodiversity �including birds, herpetofauna, butter-flies, mammals, and plants� across land ownershipcategories, in landscape patches containing largelynatural vegetation . We also examined the extent towhich differences may be explained by indirect,landscape-level features including the length of thepatch perimeter, the patch perimeter-to-area ratio, andthe relative isolation of the site from other natural ar-eas. We analysed the numbers of both globally-, andregionally-rare biota, from an array of natural areasin southern Ontario, as indices of regional biodiver-sity, in order to evaluate the conservation importanceof land ownership and these other, landscape-levelfactors.

Methods

Study region

We studied the distribution of globally- and region-ally-rare organisms in 344 protected natural area�NAs; see following section for details� in southernOntario, Canada �see Figure 1�. This region has beenexposed to intense anthropogenic pressure, possiblygreater than any other region in Canada. Geographi-cally, the region comprises less than one percent ofCanada’s land area yet contains 25% of the popula-tion �Government of Ontario 2000�, with some esti-mates projecting 40% by 2026 �Government ofOntario 2000�. Southern Ontario sits at the northernedge of the Eastern Deciduous Forest Region ofNorth America �Theberge 1989; Delcourt and Del-court 2000�; natural vegetation includes deciduousforest, tallgrass prairie and savanna, and wetland sys-tems. There is considerable climatic ameliorationfrom the Great Lakes �Theberge 1989�, which hasfavoured European settlement and agriculture overthe past three centuries. Native people used the regionagriculturally, prior to European settlement. Develop-ment of the region was also facilitated by the readysupply of rock and aggregate in the Niagara Escarp-ment, a 750 km, largely forested, Paleozoic limestoneescarpment that is the most prominent topographical

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feature in the region, after the Great Lakes �Riley etal. 1996; Lovett-Doust and Kuntz 2001�. We havepreviously demonstrated the importance at natural ar-eas of the Niagara Escarpment World Biosphere Re-serve of land ownership, as well as certain landscape-level factors associated with the escarpmentenvironment �and not examined here� – including thenumber of geological landforms, and the extent of in-terior forest on various biotic indicators �Lovett-Doust and Kuntz 2001�. We also recently reportedsignificant effects due to land-use in the backgroundmatrix of land surrounding these escarpment sites�Biernacki M., Lovet-Doust J., Page R.; unpublisheddata�.

Historically-continuous deciduous forest in the re-gion has decreased significantly and become highlyfragmented �Pearce 1993; Larson et al. 1999�. Atpresent, forest cover ranges from 7 � 40% �mean �24.8%� of its pre-settlement extent �Larson et al.

1999�. Consequently remaining species have beenconcentrated within smaller, more isolated, naturalareas that exist scattered across the regional land-scape.

Data collection

An electronic database was created using publishedinformation for physical and biological features at344 remnant areas of natural habitat, all of which hadpreviously been designated as environmentally signif-icant areas �ESAs� by Ontario Conservation Authori-ties �Oldham 1983; Heagy 1993, 1995�. These naturalareas had been identified as important and valuablebecause: 1� they contained particular natural features�such as significant geological landforms, high levelsof biodiversity, rare species, or rare communitytypes�; 2� they provide important services for wildlife�e.g., serving as migratory staging grounds, or part of

Figure 1. Map of study area �encompassed by thick line� with 289 NAs in southern Ontario, Canada. The Niagara Escarpment BiosphereReserve is marked by shaded area. Lines indicate shorelines of lakes and rivers.

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a habitat linkage system�; or 3� they offer particularvalue for aesthetic, recreational, scientific, or educa-tional purposes. The designation of “environmentallysignificant” confers a certain level of recognitionupon a NA, but otherwise carries no particular pro-tective status �Oldham 1983; Heagy 1993, 1995�.

Biotic inventories �mostly published within thepast 10-12 years� of NAs had been carried out by ex-perienced biologists from either the Ontario Ministryof Natural Resources �OMNR� or regional Conserva-tion Authorities, and utilized extensive field studies,faunal trapping, and surveys �Table 1�. The primarypurpose of these inventories had been to characterizeregional features as fully as possible, hence intensityand accuracy of field surveys were similar acrossnatural areas, regardless of ownership status. Our da-tabase was developed using published results of in-ventories for 344 NAs, though complete informationabout both area and ownership were available foronly 289 NAs. Table 1 summarizes data sources forthese NAs.

Species rarity ranks

We determined regional distribution and abundancestatus for each species reported as present at a NA anddesignated as having conservation significance inOntario �i.e., identifed as being rare, in terms of ei-ther its global distribution and abundance �“G-rank”�or its regional distribution and abundance �“S-rank”��.G- and S-ranks have five point scales, with 1 repre-senting the very rarest �at either global or regionalscales�, and 5 representing the most common �Master1991�. Information was determined for mammal, am-phibian, reptile, bird and butterfly faunal groups fromthe Natural Heritage Information Centre, OntarioMinistry of Natural Resources, Peterborough, Ontario�NHIC 1999�. Global and regional rarity ranks for

plants were taken from Newmaster et al. �1998�. Fol-lowing convention, in our analyses species designatedas either G1, G2, or G3 were regarded as “globallyrare” and species designated as S1, S2, or S3 wereclassed as “regionally rare”. For taxa with uncertainconservation status �e.g., S3S4, or G1G2�, the taxonwas conservatively assigned the more rare designa-tion �S3 or G1, respectively, in the above example�.

Land ownership

Ownership of each NA was assessed from individualsite descriptions in the ESA reports, and NAs wereassigned to one of four ownership categories: private;public; mixed ownership; First Nations �tribal/bandowned�. There were so few tribally-owned NAs thatthis category was excluded in analyses. Private own-ership meant the NA was owned and managed by ei-ther one or more private landowners. In contrast apublicly-owned NA was owned and managed eitherby some level�s� of government �municipal, county,provincial or federal�, or by a public agency, such asan Ontario regional Conservation Authority. In manycases, part of the area of a NA belonged to a publicjurisdiction while the reminder was privately owned;these were treated as mixed ownership.

Landscape parameters of NAs

Digitized maps for each NA �available from OntarioMinistry of Natural Resources �OMNR�, or regionalConservation Authorities� were used to calculate spa-tial parameters, including area, perimeter and an es-timate of shape. Digitized maps �of the same scale1:25,000� were analysed using ArcView software v.3.2 �Environmental Systems Research Institute, Red-land, CA�. For each NA, we determined area and pe-rimeter relations as follows.

Table 1. Data sources for natural areas in southern Ontario, by locality.

Locality Number of NAs Data sources

total analysed1

Essex County 50 50 Environmentally Significant Area �ESA� data assembled using information from Oldham�1983 �updated 1991�� and Kamstra et al. �1995�

Hamilton-Wentworth 102 85 Heagy �1993, 1995�Metropolitan Toronto 135 117 Metropolitan Toronto and Region Conservation Authority �1982, plus updates of 1994,

1995, and 1996�Lower Trent Region 38 37 Brownell and Blaney �1995�

1NAs for which data about area and ownership were available

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An index of perimeter-to-area was calculated to re-present the degree of fragmentation for each NA. Weused the sum of the external perimeter �Pext.� plus thecumulative length of interior perimeter �Pint.� gener-ated by any roads, railroads or powerline corridorswithin an NA:

Perimeter-to-area ratio � �Pext � Pint.� ⁄ A

where A � area of NA. Isolation of NAs was evalu-ated as the shortest distance from the perimeter of oneNA to the perimeter of the next-nearest NA. Thenumber of other NAs within a 10 km contour, radiat-ing from the patch perimeter, was determined for eachNA.

Estimates of habitat diversity were made for eachNA following the Ecological Land Classification forSouthern Ontario �Lee et al. 1998�. This system rec-ognizes six nested levels, ranging from site region,through community series, to vegetation type. We de-termined the number of community series in each NA�e.g., swamp, marsh, deciduous forest, grassland�.

Statistical analyses

Effects of landscape-level traits of NAs on numbersof rare species per NA were analysed using analysisof variance, analysis of covariance, and linear regres-sion using Systat �Systat for Windows v.10, SPSS Inc.Chicago, IL�. Ownership was treated as a categoricalvariable; area, perimeter length, perimeter-to-area ra-tio, extent of elongation �longest axis fitted in thecontour of NA divided by longest perpendicular axis�,and isolation �distance to nearest NA� were treated ascontinuous variables. In multi-factorial regressions, astandard stepwise backward procedure was used toidentify the most significant independent variablesand to maximize power and determination of the co-efficient of regression �Zar 1999; Systat for Windowsv.10, SPSS Inc. Chicago, IL�. Pearson correlations ofspecies richness of rare biota and associated probabil-ities were also evaluated. A non-linear procedure wasused to estimate the optimal exponent of power-basedspecies-area relationship functions for each group ofbiota according to the following model:

S � C AZ

whereS � number of species in biotic group;

C � coefficient for area;A � area of NA;Z � exponent for area.

A least squares procedure utilizing the Gauss-Newton algorithm and available in Systat was usedto estimate the optimal parameters of species-area re-lationship. Prior to linear analyses, all variables wereevaluated for normality of distribution and, whennecessary, log �n�1� transformations were applied�Zar 1999�.

Results

The array of rare species represented in individualNAs was quite low in terms of absolute numberswithin biotic groups present in any one NA, howeverthere was considerable heterogeneity �Table 2�. Forexample, at several NAs, all three of Ontario’s glo-bally rare herptile species occurred; at another site, 49bird species, or 68% of all Ontario’s regionally-rarebird species were recorded. Indeed, two �of a total ofeleven� and 49 �of 72� globally-rare, and regionally-rare bird species, respectively, occurred in singleNAs; yet overall there were just two NAs which con-tained more than twenty, regionally-rare birds. Nearlyall NAs having any regionally-rare birds at all, con-tained just 1 � 4 of these species. Regionally-rareplants �with 732 species recorded in Ontario� had thegreatest general representation, yet on average only c.6% of all regionally-rare plant species occurred ateach NA.

Ownership

About half the NAs �157 sites� were ownedcompletely by private interests, a further quarter �77sites� by a mixture of private and public ownership,while about a fifth �55 sites� were owned by one ormore public jurisdictions. The frequency distributionof sizes, and the mean area of NAs in each owner-ship group differed �Figure 2�. Privately-owned NAsdominated; by area, privately-owned NAs contributednearly 49% of the total area of analysed NAs, whilemixed ownership gave 36%, and public ownershipjust 15%.

Analysis of covariance �with area treated as cova-riate� identified ownership as a significant influenceon rare-species richness. With the exception of glo-bally-rare birds and herptiles, and regionally-raremammals, ownership had significant effects on the

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numbers of all groups of rare species �Table 3�. Fur-thermore, wherever there was a significant difference,publicly-owned sites had significantly greater num-bers of rare biota than other forms of ownership�Table 3�. For globally-rare butterflies, ownership hadeven greater effects than did effects of area. In thecase of globally-rare butterflies, ownership accountedfor over 12% of variation, while area alone explainedonly 0.15% of variation �see Table 3�.

Area

Area per site ranged from � 1 ha to 2400 ha �Figure2�. Most sites were relatively small; more than threequarters of NAs had area � 100 ha and more thanhalf the NAs had area � 65 ha. Mean and median ar-eas were 163.3 ha �SE� 17.1� and 64.6 ha, respec-tively. Only three sites had area � 2000 ha. Forprivate sites, mean area was158 ha �median 85 ha,range 0.9 to 1278 ha�, and for public sites it was132ha �median 16 ha, range 0.1 to 1481 ha�. At mixedownership sites the mean was 249 ha �median 61 ha,range 0.5 � 2400 ha�. A nonparametric Kruskal-Wallis test indicated that private NAs were signifi-cantly larger than mixed and public sites �teststatistic�11.63, P�0.009, df�2�. Areas of public andmixed ownership did not differ significantly in size.

Analysis of covariance showed that without regardto type of organism, 28.3% of variation in the num-ber of rare species was explained by variation in area.Overall, variation in area accounted for 0.2% to 29%of variation in rare species numbers, with lower val-

ues for globally-rare taxa than for regionally-rareones �Table 3�. In general, with increasing area therewas a significant �R2�0.04; df�1, 219; F�9.13;p�0.003� decrease in distance to nearest NA; therewas also a significant relationship �R2�0.021; df�1,221; F�4.80; p�0.03� between size of NA and num-ber of other NAs within a 10 km distance �Figure 3�.Smaller sites were more isolated and were less likelyto have other NAs within a 10 km distance. Isolationor number of other NAs varied enormously for smallNAs �from extremely isolated to not isolated at all�,whereas degree of isolation for large NAs was con-sistently low �Figure 4�

Landscape traits of NAs

Numbers of species of both globally- and regionally-rare biota decreased significantly �R2�0.43; df�1,44; F�29.75; p � 0.001 and R2�0.34; df�1, 203;F�104.1; p � 0.001 respectively for globally- andregionally-rare biota� per unit area as the size of NAincreased �Figure 4�. The smallest NAs were mostlikely to have the greatest number of rare biota perunit area. Shorter distance to other NAs was signifi-cantly �R2�0.07; df�1, 203; F�6.61; p�0.011� re-lated to larger numbers of rare biota at a NA. Incontrast to effects of area, perimeter-to-area ratio didnot have significant direct effects on the number ofrare species at a NA. However, regression analysesindicated a highly significant �R2�0.18; df�1, 202;F�19.84; p � 0.001� negative relationship betweenperimeter-to-area ratio and NA plant community di-

Table 2. Distribution patterns for globally- and regionally-rare biota in natural areas �NAs� in southern Ontario. �N � number of NAs havingdata for a particular biotic group�.

Biotic Group N Total number ofspecies re-corded in On-tario

Maximum num-ber of speciespresent in anindividual NA�% of total�

Mean number��SE� of spe-cies at each NA

Number of NAs having particular num-bers of rare species:

0 1-4 5-10 11-20 � 20

Birds Globally rare 240 11 2 �18%� 0.02 �0.01� 238 2 0 0Regionally rare 278 72 49 �68%� 0.76 �0.24� 210 63 3 0 2

Butterflies Globally rare 94 5 2 �40%� 0.15 �0.08� 90 4 0Regionally rare 94 44 14 �32%� 0.78 �0.19� 60 32 1 1 0

Mammals Globally rare 232 1 0 0 0 0Regionally rare 232 15 5 �33%� 0.06 �0.03� 223 8 1 0

Herptiles Globally rare 168 3 3 �100%� 0.18 �0.04� 150 18Regionally rare 236 18 12 �66%� 0.34 �0.08� 204 27 4 1

Vascularplants

Globally rare 242 32 6 �19%� 0.14 �0.04� 222 19 1 0 0Regionally rare 289 732 113 �15%� 4.70 �0.62� 157 85 29 26 19

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versity. Furthermore plant community diversity hadhighly significant effects on rare-species richness inall biotic groups, except for globally-rare butterflies�Table 4�.

The number of other NAs in a 10 km radius from aNA was significantly correlated with number of rarespecies observed �R2�0.07; df�1, 191; F�6.79;p � 0.008�. Effects of the presence of other NAswithin a 10 km radius were significant for richness ofglobally-rare biota �R2�0.04; df�1, 44; F�4.97; p �0.031� and for regionally-rare biota �R2�0.12; df�1,201; F�9.62; p � 0.002�.

Biotic variables

Mean number of plant communities was 4.6 �median4, range 1- 13� at private NAs, 4.1 �median 3, range1-12� at mixed ownership NAs, and 3.8 �median 3,range 1-16� at public NAs. The nonparametricKruskal-Wallis test did not indicate significant differ-ences in plant community diversity among the threeownership groups �test statistic�4.24, P�0.24,df�2�. Univariate regression analyses indicated thatcommunity diversity was highly significantly corre-lated with the number of rare biota at each NA. Re-gression coefficients differed for each group of rarebiota and were greatest for regionally-rare plants.Community diversity accounted for between 2.1% ofvariation in species number �for globally-rare plants�to 31% of variation in species number for regionally-rare butterflies. Furthermore, for all but regionally-rare birds, the proportion of variance in values forrare animal species richness accounted for by com-munity diversity exceeded the variance accounted forby area �e.g., 2.8% vs 13.9% for globally-rare birds;Table 4�. In contrast, variance in the number of rareplant species was better accounted for by the area ofNAs than by community diversity. Area was highlysignificant �N�289, p � 0.001� and itself accountedfor c. 45 % of variation in plant community diversity.Perimeter-to-area ratio also had highly significant ef-fects �N�289, p � 0.001� and accounted for a further3% of variation in community diversity. Thus, botharea and the perimeter-to-area ratio had possible in-direct influences on rare biota suggested by their cor-relation with community diversity.

Figure 2. Frequency distribution of area of NAs in different own-ership classes.

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Discussion

Public NAs in Ontario harbour significantly greaternumbers of species, particularly of globally and re-gionally rare biota, than do private NAs. This obser-vation in particularly striking because, in southernOntario, private NAs dominate by number, by cumu-lative area and by average area of NA. This situationmay be a consequence of historical events related toprotection of particular NAs, and implementation ofconservation programs at the NAs. Yet despite a ma-

jor importance of public NAs in protecting rare biotain southern Ontario, both public and private NAs har-bour unique rare species found nowhere else, thuscomplementing each other in conservation of rarebiota �Heagy 1993, 1995�. In contrast, preliminarystudies of rare-species diversity in the United Statessuggest that private lands harbour rather greater num-bers of rare and imperiled species than public lands�USGAO 1995; Stein et al. 1995; Groves et al. 2000�.

Our results show that, of several landscape-levelfactors, area had the overall greatest effects on rare-

Table 3. Summary of results of ANCOVA showing effects of NA ownership on numbers of globally and regionally rare biota. Area �asexponential function� of NA was a covariate in all models. Each ownership category was ranked numerically in decreasing order, based onrare species frequencies �different lowercase letters indicate significant ownership differences�. Significance is indicated as: * � p � 0.05; **� p � 0.01; *** � p � 0.001.

Biota N R2 F- ratio for ownership Ownership rank Exponent for area F- ratio for area

Public Mixed Private

Globally rare birds 237 0.039 1.157 1a 2a 3a 0.009** 8.196**Regionally rare birds 274 0.110 8.604*** 1a 2b 3b 0.110*** 23.187***Globally rare butterflies 117 0.125 7.977*** 1a 2b 3b 0.004 0.074Regionally rare butterflies 117 0.257 3.287* 1a 3b 2ab 0.220*** 30.951***Regionally rare mammals 237 0.025 1.758 1a 3a 2a 0.006 3.411Globally rare herptiles 237 0.023 1.577 1a 2a 3a 0.018* 5.272*Regionally rare herptiles 237 0.279 2.980* 1a 2ab 3b 0.057*** 16.440***Globally rare plants 289 0.050 3.313* 1a 2ab 3b 0.022* 8.422**Regionally rare plants 289 0.100 5.580*** 1a 2b 3b 0.203*** 21.867***Globally rare biota 289 0.065 4.071** 1a 2b 3b 0.037** 13.363***Regionally rare biota 289 0.121 5.174** 1a 2b 3b 0.270*** 32.645***Total rare biota 266 0.283 2.952* 1a 2ab 3b 0.618*** 92.645***

Figure 3. Relationship between area of NA and �A� distance to nearest NA; and �B� number of NAs within a 10km distance from perimeterof NA. Lines represent linear regression and 95% confidence interval.

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species richness and other biotic indices. Effects ofarea were followed by effects of plant community di-versity, however this was itself significantly affectedby area and the extent of perimeter �a function ofshape� of the NA. Both these factors were followedby effects of ownership of the NA, and by effects ofisolation of the NA from other NAs �represented byminimum distance to nearest NA, and by number ofNAs in 10 km radius�. Other landscape-level factorsdid not appear to have overall significant effects.

Ownership of land

The concept of private ownership of land is one ofthe most important structural attributes of NorthAmerican society, and it imparts great leeway to theowner in land-use decisions. These directly impactbiota utilizing the land as habitat, migratory stagingpoints, etc. �Platt 1996; Vitousek et al. 1997; Daily1997; Dale et al. 2000; Government of Ontario,2000�.

Land-owners experience economic pressure toconvert land-use to development, or for agriculturalproducts �Costanza et al. 1997; Adger and Luttrell

Figure 4. Number of �A� globally-rare biota-, and �B� regionally-rare biota per unit area �ha� of NA.

Table 4. Proportion of variation in rare species richness accounted for by NA area and plant community diver-sity. Significance is indicated as: * � p � 0.05; ** � p � 0.01; *** � p � 0.001

Biotic group Coefficients of determination �R2� for:

Area Community diversity

Birds Globally rare 0.028** 0.139***Regionally rare 0.118*** 0.106***

Butterflies Globally rare 0.002 0.022Regionally rare 0.288*** 0.312***

Mammals Globally rare – –Regionally rare 0.005 0.065***

Herptiles Globally rare 0.017* 0.075***Regionally rare 0.070*** 0.166***

Vascular plants Globally rare 0.019* 0.021**Regionally rare 0.096*** 0.056***

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2000�. Lack of clear understanding of the values ofbiodiversity and related ecosystem services and, in-deed, inadequate bases for quantifying these values,means these are often given too little weight in deci-sions about land conversion �Costanza et al. 1997�.

Three studies have mapped the overall distributionof species and land ownership in the U.S. Stein et al.�1995� examined the importance of U.S. federal landsfor maintaining federally-listed, endangered species:only half of such species occurred at all on federallands. A study by the U.S. Government AccountingOffice �USGAO 1995� reached a similar conclusion�through different methodology�: one-half to two-thirds of federally-listed species occurred �non-exclu-sively� on federal lands. Finally, Groves et al. �2000�examined the distribution in the U.S. of species withfederal status, and assessed the distribution of thosespecies classified as globally imperiled �i.e., havingG1 or G2 status�. Federal land supported nearly 60%of the federally-listed endangered species and aboutthe same fraction of imperiled species. State landcontained at least one population for 43% of imper-iled species and 58% of federally-listed species.Among major federal agencies, Dept. of Defenselands appeared to contain the greatest numbers offederally-listed species, while Forest Service landshad most imperiled species. In contrast, private landin the U.S. holds at least one population of � 50% ofall imperiled species and c. 66% of federally-listedspecies �Groves et al. 2000�. Southern Ontario hasone of the greatest fractions of land in private own-ership in Canada �Ramsey 1988; Government of On-tario 1997�. Private NAs dominate numerically andby area �about three times the number and the area ofpublic NAs� �see Figure1�. Yet numbers of rare biotaand plant communities per unit area and per NA weregreatest on public lands �Table 3�. Our results corre-spond to the general conclusions of Thomas et al.�1997� who determined that old woodlands � � 400years� in Britain had greater species richness when onpublicly- and trust-owned lands than when they werelocated on private- and estate-owned lands.

Spies et al. �1994� found that over the course of 16years, initially-continuous conifer forests on publiclands had three times more area overall, with moreclosed canopy and three times more interior forest,than otherwise comparable, privately-owned lands. Insouthern Ontario, studies have shown that the largestintact patches of forest were publicly owned, underthe jurisdiction of Ontario Ministry of NaturalResources �Pearce 1993�. Furthermore, privately-

owned lands surrounding nearby public lands weremore fragmented and had highly isolated woodlots�Pearce 1993�. Similarly, in an analysis of 98 envi-ronmentally significant natural areas along the Nia-gara Escarpment in southern Ontario, Lovett-Doustand Kuntz �2001� found that NAs with the largestarea and greatest extent of forest-interior habitat wereunder mixed �private and public� ownership. Privateand public NAs there did not differ in mean size, yetafter controlling for the area of the site, and for theextent of interior habitat and the degree of landformheterogeneity, biotic diversity remained significantlygreater on public land than on private �Lovett-Doustand Kuntz 2001�.

We recognize obvious limitations to our databaseand study. For example, ownership was determined ata single occasion, at the time of the NA’s inventory,and there was no record of ownership over time. Itseems likely that some of the best lands in southernOntario suitable for parks �i.e., large and highlybiodiverse� may have been purchased in the past forpublic ownership. Parks are often selected because oftheir excellent representation of regional features, andrare-species richness. Other NAs may have beenpublicly acquired more recently, or may have beentransferred as donations from private or mixed own-ership. Furthermore, simple presence of rare speciesat a location says nothing about the population via-bility or quality of the NA for rare species. Perhapsmost importantly, we have no information about themanagement practices applied at NAs over time. Fi-nally we note that, historically, land privatization didnot occur randomly, with respect to habitat types.Stressful environments have tended to be the last thatwere privatized, while fertile lands were first. Gobinet al. �2001� studied patterns of spread of land own-ership in Nigeria, and observed that lands aroundsettlements and markets were most desired, followedby land around roads and waterways, and this generalpattern spread as the human population grew and newsettlements and markets appeared. Lands far frommarkets, roads, waterways, with unsuitable landformswere least desired and remained under communalownership �Gobin et al. 2001�. Preferences ofparticular lands for private ownership have beennoted elsewhere in North America, with morepublicly-owned lands occurring at higher elevationand on soils less suitable for agricultural production�Spies et al. 1994; Craig et al. 2000; Wright et al.2001�. These lands were less desired for private own-ership because of lower suitability for agriculture and

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forestry, and difficulties with access �Spies et al.1994; Craig et al. 2000; Wright et al. 2001�. Yet itshould be noted that low-fertility soils needn’t neces-sarily mean low biodiversity. Among the most biodi-verse sites in the western United States are serpentineoutcrops in California with a tremendous number ofrare species, specifically because of their low fertility�Ricketts et al. 1999�. Similar observations have beenreported for New Zealand �Craig et al. 2000� where,despite the fact that 30% of all land is in reserves,most conservation land occurs in areas that are notuseful for production. The same conclusions seemlikely for the intensely settled and highly agricultur-alized land of southern Ontario.

Government and other public sector investment isclearly important for the conservation of biodiversity,and for several reasons may even be preferable toprivate sector investment �see James et al. 2000�. Atpresent, the private sector is less prepared to providepublic goods which are related to the global environ-ment �such as the values and services of biologicalsystems and resources� �Wilson 1992; James et al.2000�. Estimates of economic value for the goods andservices that undisturbed natural areas provide aresorely needed to bolster any economic argument forprotection of natural areas and to counterbalance themore readily apparent short-term benefits of develop-ment �Cairns and Bidwell 1996; Costanza et al. 1997;Daily 1997�.

Landscape-level traits of NAs

Results of this study indicate that area was the mostimportant factor, accounting for about a third of totalvariance in numbers of rare species. However, effectsof area differed among ownership classes for numbersof both globally- and regionally-rare species, withsignificantly larger numbers on comparably-sizedpublic land than on private �Table 3�. From the per-spective of rare-species conservation, greater biodi-versity of rare species per unit area occurred in smallsites compared to larger ones �Figure 4�. Of course,simple presence alone does not indicate that popula-tions are viable, especially for animal species. Ourresults show for some biota, plants in particular, thateven relatively small areas supported a disproportion-ately large number of rare species �though we notethat, at least for birds, problems affecting survivorshipand fecundity occur disproportionately often insmaller woodlots �Burke and Nol 2000��. Further-more, depending on location, numerous small NAs

may serve as temporary staging areas and transfercorridors for biota that migrate among habitat patches�Falkner and Stohlgren 1997; Keitt et al. 1997; Haleet al. 2001�. While smaller NAs may be sufficient forprotection of rare plants, most animals � amphibians,reptiles, mammals and birds, may require substan-tially larger tracks of land for their home ranges. Ourresults indicate that NAs in southern Ontario weregenerally too small to provide habitat for globally andregionally rare mammals.

Few effects of fragmentation �estimated as perim-eter-to area ratio� were observed; the number of plantcommunities was the sole variable responsive tofragmentation. However, fragmentation effects onplant community diversity may have carry-overeffects on rare biota, since rare-species richness wassignificantly dependent on these communities. Burkeand Nol �2000� found woodlot area was the most im-portant factor affecting reproductive success offorest-breeding birds in Ontario, with local plantcommunity diversity having no apparent effects. Bycomparison, Freemark and Merriam �1986� observedsignificant effects of plant community diversity,greater than the effects of habitat area, on diversity ofbird species in fragmented forests of southernOntario. Plant community itself was found to be sig-nificantly affected by perimeter-to-area ratio. In sum,results of our study suggest that area was the domi-nant factor affecting species richness in NAs,followed by effects of plant community diversity,ownership, perimeter-to-area ratio, and isolation.

Acknowledgements

We are grateful to the Natural Sciences and Engineer-ing Research Council of Canada for financial supportto JLD. We appreciate valuable comments from L.Fahrig, A. Hegazy, L. Lovett-Doust, H. MacIsaac, G.Merriam, M. Oldham, W. H. Romme, P. Sale, W.Reid, and three anonymous reviewers. We acknowl-edge the reports and surveys of natural areas providedby regional Conservation Authorities at Essex, MetroToronto, Lower Trent Region, and Hamilton-Went-worth Region.

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