Investigation, evaluation, and priority ranking of natural areas

INVESTIGATION, EVALUATION, AND PRIORITY RANKING OF NATURAL AREAS* FREDERICK R. GEHLBACH,

Institute of Environraental Studies, Baylor University, Waco, Texas 76703, USA ABSTRA CT Texas experience suggests that amateur naturalists will be heavily involved in preliminary ecological surveys of natural areas, hence a simple key for identification of community-types is presented. Line intercept transects are suggested for amateur use in providing standardised quantitative data on the physiognomy of natural areas. A scheme for the evaluation of each area utilises the weighted values of climax condition, educational suitability, species significance, community representation, and human impact through multiplicative scoring to give a natural area score. With the weighted values-multiplicative scoring scheme, natural areas are clearly distinguished in priority for acquisition.

INTRODUCTION Half a century ago a committee of ecologists published the first inventory of natural areas in the Americas (Shelford, 1926). Since then surveys of natural areas have proliferated in response to the steady decline of native landscapes. World inventories are conducted by the International Biological Programme and International Uffion for the Conservation of Nature, while United States inventories are conducted both Federally (U.S. Department of Interior) and privately (The Nature Conservancy). Even certain states have made comprehensive surveys (e.g. Lindsey et al., 1969; Smith, 1974). Justification for the protection of natural areas is well documented (Moir, 1972; Jenkins & Bedford, 1973). These lands, where man's influence is minimal, are important for three basic reasons: (1) as outdoor classrooms, wherein the use of resources is educational and hence non-consumptive, (2) as controls, against which to measure human impact in cultural landscapes, and (3) as living museums * Paper presented at the symposium, The Natural Areas of Texas, sponsored by the Texas Academy of Science, 1 March 1974. 79 Biol. Conserv. (8) (1975)--© Applied Science Publishers Ltd, England, 1975 Printed in Great Britain

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of genetic diversity. No longer is there any doubt that natural landscapes are valuable for purposes other than economic exploitation. Texas continues to modify its natural landscapes, so the Texas Natural Areas Survey was organised privately in 1966 to provide natural history background for the state's transfiguration. The 851 sites described qualitatively demonstrate the richness of Texas' natural heritage (Texas Natural Areas Survey, 1972). However, the statewide inventory must continue with quantitative surveys and a site evaluation procedure that lends objectivity to the preservation process. This paper presents information generated specifically for Texas' future efforts, but the methodology has potential application beyond the state's political borders.

IDENTIFICATION AND INVESTIGATION

Amateurs outnumbered professional biologists three to one in contributing to the Texas Natural Areas Survey (1972). Moreover, the ratio of resident bird-watchers to professional ornithologists (8:1 in 1971; members of the Texas Ornithological Society compared with those of the American Ornithologists Union) is exemplary of the relative abundance of amateurs and paucity of professionals available for future natural areas surveys. A survey organisation cannot afford to devise such complex techniques of investigating and identifying natural areas that only professionals can use them. Vegetation is usually the easiest identifier of natural communities, since it is present in all seasons and more easily counted or measured than the fauna. Because vegetation changes with season and along environmental gradients, its physical description at points of change will identify the general ecological nature of a natural area (cf. Goldsmith, 1974). To facilitate identification of communitytypes in Texas, a simple dichotomous key based on major physical media and simple vegetative life-forms is offered (Table 1). This key is self-explanatory and hence useful to the amateur naturalist. It is inspired by Fosberg (1967) and adaptable for other regions. With a guide to community-type identification in hand, it is then necessary to devise standard survey methods, easily accomplished by amateurs without special equipment. Measuring tapes are generally available along with field guides to species identification, so line intercept transect counts or measurements of individuals per species or lineal coverage per species are recommended. Such assays should be conducted in each physical subdivision of a site (hilltop, hillside, floodplain, etc.) in the growing season. If time permits, and especially if the dominant vegetation is herbaceous, line intercept transects might be used at other seasons too. In forest, woodland, or desert, trees and shrubs can be counted along 50 foot (15.25 m) transects, whereas the lineal coverage of grasses and forbs is more easily

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TABLE 1 DICHOTOMOUS KEY FOR IDENTIFICATION OF COMMUNITY-TYPES DOMINATED BY VASCULAR PLANTS IN TEXAS

1. Standing or running water present most of the year . . . . 2 Dry or moist land most of the year . . . . 7 2. Trees dominant . . . . 3 Shrubs or herbs (forbs) dominant . . . . 4 3. Trees grow primarily in shoreline area . . . . OXBOW L A K E OR BAYOU Trees grow throughout.. :.. SWAMP 4. Shrubs dominant . . . . BOG Herbs (forbs) dominant . . . . 5 5. Water fresh . . . . F R E S H W A T E R MARSH Water brackish (salty) . . . . 6 6. Gulf coastal plain . . . . SALT M A R S H Inland . . . . ALKALI M A R S H 7. Trees dominant . . . . 8 Shrubs or grasses dominant . . . . 11 8. Trees average less than 25 ft (7"61 m) in height; open canopy . . . . 9 Trees average more than 25 ft (7.61 m); closed canopy . . . . 10 9. Evergreen trees dominant . . . . E V E R G R E E N W O O D L A N D Deciduous trees dominant . . . . D E C I D U O U S W O O D L A N D 10. Evergreen trees dominant . . . . C O N I F E R O U S FOREST Deciduous trees dominant . . . . D E C I D U O U S FOREST 11. Shrubs dominant . . . . 12 Grasses dominant . . . . 13 12. Succulent shrubs dominant . . . . S U C C U L E N T DESERT Non-succulent shrubs dominant . . . . SHRUB DESERT 13. Grasses average less than 1 ft (30.5 cm) in height . . . . SHORT GRASS PRAIRIE Grasses average more than 1 ft (30'5 cm) in height . . . . TALL GRASS PRAIRIE

m e a s u r e d t h a n c o u n t e d in a q u a t i c c o m m u n i t y - t y p e s a n d prairies. F l o a t i n g o r e m e r g e n t a q u a t i c v e g e t a t i o n p e r u n i t o f s t r e a m , p o n d , o r m a r s h s h o r e l i n e is readily d e t e r m i n e d i f n o t easily identified to species b e c a u s e o f inaccessibility. T h e n densities o r c o v e r a g e s a r e used to d e t e r m i n e c o m m u n i t y - t y p e s ( p l a n t f o r m a tions) a n d d o m i n a n c e - t y p e s . It is t h e large a n d c o m m o n l i f e - f o r m s t h a t define a n a t u r a l area. A c o m m u n i t y - t y p e is d e t e r m i n e d f r o m the l i f e - f o r m o f t h e tallest a n d m o s t a b u n d a n t p l a n t s tallied ( T a b l e 1). E x p e r i e n c e in T e x a s suggests t h a t 7 0 % is a w o r k a b l e rule ( G e h l b a c h , 1967). F o r e x a m p l e , if 7 0 % o r m o r e o f t h e p l a n t s in a t r a n s e c t are d e c i d u o u s , taller t h a n 25 ft (7.61 m), a n d t h e tree c a n o p y is closed, d e c i d u o u s f o r e s t is i n d i c a t e d . O r i f 3 5 ft (10.67 m) o f a 50 ft (15-25 m) t r a n s e c t is grass c o v e r taller t h a n 1 ft (30.5 cm), a tallgrass p r a i r i e is d e s i g n a t e d . Species o r g e n e r a r e p r e s e n t e d by 20 % o r m o r e o f t r a n s e c t i n d i v i d u a l s o r lineal c o v e r a g e are r e c o g n i s e d in d o m i n a n c e - t y p e e p i t h e t s in o r d e r o f their i m p o r t a n c e . T h i s f u r t h e r d e s c r i b e s a n a t u r a l a r e a ( T a b l e 2).

Pinus eehinata Mill. Liquidambar styraciflua L. Quereus marilandica Muenchh. Carya tomentosa Nutt. Ulmus crassifolia Nutt. Quercus stellata Wang. Quercus stellata Wang. Pinus eehinata Mill. Ulmus crassifolia Nutt. Carya tomentosa Nutt. Liquidambar styraciflua L. Quercusfalcata Michx. Quercus marilandica Muenchh. Pinus echinata Mill. Quercus stellata Wang. Ulmus (cf. alata) Michx. Liquidambar styraciflua L. Betula nitra L. Acer rubrum L. Pinus taeda L. Ulmus americana L. Quercus nigra L. Viburnum nudum L. Betula nigra L. Liquidambar styraciflua L. Quercus nitra L. Acer rubrum L.

UPLAND ROCKY RAVINE; North and southfacing slopes with sandstone outcrops; 10--30° gradients (ca. 10 acres (4.16 ha), 5 transects).

UPLAND EAST-FACING SLOPE; no surface rocks; sandy soil; less than I0 ° slope (ca. 20 acres (8.32 ha), 4 transects).

U P L A N D PINE STAND; 5-10 ° East-facing slope; very loose sandy soil (ca. 10 acres (4-16 ha), 4 transects).

LOWLAND FLOODPLAIN; sandy clay alluvium; little gradient (ca. 25 acres (10'40 ha), 4 transects)

LOWLAND BOG-STREAM ; mucky peat ; standing and flowing water; little gradient (ca. 10 acres (4.16 ha), 3 transects)

* Total individuals of species averaging <25 ft (7"61 m) high (V. nudum excepted).

Species and individuals*

Physical subdivision

18 13 12 8 5

14 6 4 3 2 1

29 3 3

16 9 7 5 2 2 2

10 9 5 4 4 3

Possum Haw (32%)-River Birch (23 %)Sweetgum (21 ~ ) Dominance-type

D E C I D U O U S FOREST (100 %)

Sweetgum (47 %)-River Birch (20 ~ ) Dominance-type

D E C I D U O U S FOREST (90 ~ )

Shortleaf Pine (83 %) Dominance-type

C O N I F E R O U S FOREST (83 ~ )

Oak (46 %)--Pine (21 ~ ) Dominance-type

D E C I D U O U S FOREST (79 ~o)

Pine (29 ~o)--Sweetgum (26 %)Oak (23 ~ ) Dominance type

D E C I D U O U S FOREST (71%)

Community and dominance-types

TABLE 2 PHYSICALAND VEGETATIVEFEATURESOF SHEFF'SWOODS,SMITHCOUNTY,TEXAS

m t~ >

m

Oo tO

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Survey results can be illustrated by summarising the initial inventory of Sheff's Woods, a 75 acre (31.2 ha) site in Texas investigated by amateurs to validate methodology (Table 2). Five physical subdivisions were located in the site's environmental gradient from upland, warm-dry hillsides to lowland, cool-wet floodplain and stream. The larger the size and/or diversity of the subdivision, the more transects placed there. The general appearance of vegetation suggested that the largest woody plants would furnish the most information about the site, so tree intercept transects were employed. The Sheff's Woods inventory required about 35 man-hours, 20 of which were spent in general reconnaissance with the land owner and the remainder in making the transect counts, identifications, and calculations. In addition, however, the stream was seined for fishes, small mammals were live-trapped, and the landscape was searched for small and uncommon plants and vertebrates. These efforts located the black oak (Quercus velutina Lam.) and creek chub minnow (Semotilus atromaculatus Mitchill) at their western limits of range in the state. Without such special survey methods to augment the transect approach, our 'invisible heritage' of rare, relict, and peripheral species may be overlooked. In the future, the Texas Natural Areas Survey will attempt to code the results of site inventories in a manner suitable for digital computerisation (cf. Aultfather & Crozier, 1971; Dallas Department of Planning and Urban Development, 1973). In the information retrieval phase, the survey will generate natural area maps on which a scale of abundance to rarity and location of features are given. This will be accomplished for community-types first, then for dominance-types and selected species (indicator and endangered species initially). Other aspects such as incidence of, and relative resistance to, human impact can be superimposed on the maps once successional dynamics are known.

EVALUATION AND PRIORITY RANKING

Evaluating and ranking natural areas in a standardised fashion for acquisition is as essential as standardised survey procedures and computer synthesis of survey data. Conservation organisations and land management agencies typically want a list of the most significant areas. What are the considerations? Qualitative and quantitative methods are available for other kinds of landscape evaluation (Tubbs & Blackwood, 1971; Leopold et al., 1971), but until recently (Tans, 1974) no scheme was available for natural areas. The present evaluation scheme (Table 3) differs from those of Tans (1974) in considering the pervasive influence of man together with the features of natural communities. Tans separates human impact, natural features, and availability of areas in three different evaluations. Similarities between Tans' natural features evaluation and Table 3 are present but masked by different arrangements of the

FREDERICK R. GEHLBACH

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TABLE 3 FEATURES AND FEATURE CATEGORIES TO BE CONSIDERED IN EVALUATING NATURAL AREAS, LISTED FROM LEAST (NUMERIC VALUE = 1) TO MOST ( 5 ) IMPORTANT

Features and categories (Numerical value)

Considerations

I. HERITAGE VALUE (1) A. Late seral stage (1) B. Climax condition (2) II. EDUCATIONAL UTILITY (2) A. One special feature (1) B. Two special features (2) C. Three or more special features (3) IlL SPECIES SIGNIFICANCE (3) A. Peripheral species, hybrid zones (1) B. Rare, relict, or endemic species (2) C. Endangered species (3) IV. COMMUNITY REPRESENTATION (4) A. Two or more community-types (1) B. Community or dominance-types novel to preservation system (2) C. Localised or relict and novel types (3) V. HUMAN IMPACT (5) A. Possible but not imminent (1) B. Imminent, i.e. planned (2) C. In progress but features salvageable through succession with management (3)

Presettlement landscape; either approximating the climax or in virgin condition. Size sufficient for protection (includes buffer zones) or manipulation; history of study, present study, accessibility, demonstration value, etc. Status in world, North America, and Texas, in this order, for evaluating rarity and endangerment; Texas alone for evaluating other categories. Diversity with attention to localised or relict situations; geographic variants of a type, and coverage of existing preservation system. Degree of damage; nature of succession based on relative stress of physical environment; and suitability of restorative processes, either natural or cultural, if protection is afforded.

features to be scored. Thus, Tans divides site commonness and diversity, whereas in this paper the two are interrelated and hence joined under c o m m u n i t y representation. Tans' quality and degree o f threat features are also separated (in two different evaluation systems) but both related to h u m a n impact and so joined in Table 3. Perhaps the major innovations o f the present evaluation system are (1) its brevity, and hence utility (cf. Tans, 1974); (2) that in part it derives from a standard inventory; and (3) that it contributes to a priority ranking scheme that can use additive or multiplicative scoring o f weighted or non-weighted features. Tans' priority ranking is based on additive scoring o f weighted features, although he suggests that multiplicative scoring more accurately reflects natural area value. With such scoring the bias o f weighting is more p r o n o u n c e d and hence rank differences between areas are accentuated. Numerical values are given to five features o f natural areas in order o f their importance to natural area preservation (Table 3). Thus, it is least important whether the site is in or near climax condition and most critical to ascertain the nature and extent o f h u m a n impact. Similarly, under each feature, categories o f that feature are ranked from least to most important and given values accordingly. A natural area score is obtained by multiplying each feature value by its appropriate category value~ and adding the products. If a particular feature does not apply

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TABLE 4 COMPARISONS OF THE DISCRIMINATORY FUNCTION OF PRIORITY RANKING SCHEMES APPLIED TO NATURAL AREAS IN TEXAS

Natural areas*

Deciduous forest'l" (Smith County) Tallgrass prairie (McLennan County) Swamp-Bog complex (Tyler County) Cavernicole community (Hays County) Evergreen woodland (Starr County)

Weighted features multiplicative scoring

Weighted features additive scoring (Table 3) (Tans, 1974)

Non-weighted features multiplicative or additive scoring

23

23

17

8

35

23

19

11

40

26

21

12

40

27

19

12

43

27

21

13

* Community-types from Table 1 if epigean; features and values used in scoring from Table 3 (except Tans, 1974). t Sheff's Woods.

(e.g. no peripheral, endangered, etc. species are present), that feature value is zero. Sheff's Woods, to continue an example, is second-growth forest but approximates climax condition (1 x 1 = 1), has three or more features of educational utility (prior study, on-going research, accessibility; 2 x 3 = 6); peripheral species (black oak, creek chub; 3 x I = 3), a dominance-type novel to the Texas reserve system (possum haw-river birch-sweetgum, 4 x 2 = 8), and possible human impact (oil exploration on adjacent property, 5 x i = 5). Its natural area score is 23 (1 + 6 + 3 + 8 + 5). This gives Sheff's Woods lowest priority for acquisition among five areas similarly surveyed and evaluated for exemplary purposes (Table 4). If the weighted system is used additively, each feature value is added to its appropriate category value; and the five sums are totalled to give a natural area score. With this method Sheff's Woods scores 23 again, but all five areas are ranked so closely that distinctions are blurred (Table 4). Sheff's Woods and the tallgrass prairie, previously separated by 12 points, are now tied for lowest priority. Indeed, but four points separate the lowest from highest priority areas, whereas 20 points distinguish them with multiplicative scoring. Since there are also two ties and a four point separation with Tans' (1974) priority ranking system, its discriminatory function is equally poor (Table 4). To eliminate weighting, differential feature values in Table 3 are eliminated. Then, to achieve multiplicative scoring, each feature value equals one and is multiplied by its appropriate category value to give five products that can be

86

FREDERICK R. GEHLBACH

summed for a natural area score (Table 4). Additive scoring, through the summation of category values, gives the same score or, through the summation of feature values (= 1) plus category values, gives but five points more per area and the same poor discrimination in the priority ranking (not shown in Table 4). Withal, the weighted features-multiplicative scoring system best distinguishes natural areas for priority ranking purposes, especially if there is a long list to be compared. Utility, then, overrides the bias of weighting. Nevertheless, including particular features and weighting them differently introduces subjectivity in an otherwise objective scheme, so the raison d'etre of each feature and its weighting must be discussed.

DISCUSSION

Heritage value is a potentially important feature of natural areas, because it can be represented by climax communities (presettlement landscapes), the most stable nature provides. Climax communities are, therefore, the ultimate controls available to monitor the ultimate in destabilisation (human impact; Gehlbach, 1971). Owing to man's pervasive impact, provision is made to consider certain successional communities that approach climax conditions (late seres, Table 3). Because climaxes are scarce and difficult to define when regenerating through secondary succession, and because human disturbance is unavoidable in managing them, heritage value is given least weight among the five features to be considered (Table 3). Naturalists have begun to appreciate educational utility as ecosystem analysis gains favour and requires team study on large tracts, and as the problems of protection with buffer zones increase with increasing human impact. If an area is so small as to be damaged by repetitive use, manipulation, or surrounding culture, its educational utility is reduced. Whether a site is convenient to study or demonstrate makes a difference in utility as does its record of past and present research. The more such aspects, the greater an area's usefulness (Table 3); yet educational utility is only as good as the on-site resources and does not deserve to be weighted more than the biota itself. Species may seem to be of higher priority than communities because of the current interest in endangered species. However, this is often more apparent than real as shown by the evergreen woodland/golden-cheeked warbler (Quercus virginiana Mill-Juniperus ashei Buchh./Dendroica chrysoparia Sclater & Selvin) predicament in central Texas (Zimmerman, 1973). Since the junipers are cut for fence posts, oil, and pasture clearing, the warblers, dependent upon juniper bark for nest construction, are declining. This crisis reaffirms that species cannot live without community support and indicates that community representation should outweigh species significance (Table 3).

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Endangered species are given the highest weighting under species significance, because their small gene pools are actually or potentially most fragile. Peripheral species are weighted together with other, similar opportunities for evolutionary analysis like hybrid zones, since these require long-term protection to fulfil their resource potential. Rare, relict, and endemic species are similar scientific resources but scarce by comparison and hence deserving of more immediate attention (greater weight, Table 3). The community representation feature of natural areas is categorised so as to diversify the Texas system of natural reserves in keeping with its diverse landscape heritage. Localised or relict community-types like alkali lakes and peat bogs are the scarcest and so given the greatest weight (Table 3). Next, geographic variants of widespread community-types are protected by considering dominance-types novel to the reserve system. Community and dominance-types least likely to be generated through management, if identifiable as such, are most crucial to a reserve system. Human impact is given the highest numerical weight in the present scheme, because of man's superior ability among organisms to transfigure the biosphere. If human impact is possible, as through suburban sprawl, but not imminent, time is available to save a natural area. A more endangered site receives more attention with a higher weighting, assuming both areas are equally ranked otherwise. Thus, actual impact gets more weight than planned impact, although this evaluation requires that community-types should be salvageable. Salvageability means that impacted natural features have not completely lost their natural significance (cf. introduction, features I-IV in Table 3). Salvageability also means that losses, as through predator control or selective lumbering, can be restored naturally or culturally with management. However, salvageability varies in west to east and north to south gradients across Texas. More time is required for succession to generate climax communities in naturally stressful physical environments like the hot-dry Trans-Pecos and cool-dry Panhandle sectors than in the warm-wet forest region of southeastern Texas. Type-specific successional dynamics and management techniques must be identified. The tallgrass prairie of central Texas is an example. When Houston black topsoil is lost, this community-type cannot be restored within a century and hence cannot be considered for preservation. Conversely, if the prairie is lightly grazed, mowed for hay other than during the spring and autumn fruiting seasons, or occasionally burned in winter, climax conditions can be approximated with a decade of protection. Then the site is salvageable. Availability of a natural area through purchase or donation is not considered in the present evaluation and priority ranking scheme, because it is not a natural area value (cf. introduction, Table 3). Moreover, if multiplied into the evaluation procedure, availability modifies natural area score and thus disguises natural values. Availability is purely an economic factor that should be considered only

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after areas are ranked by natural area scores (cf. Tans, 1974). Finally, it is suggested that if offered for d o n a t i o n , an area be accepted only w h e n its natural area score exceeds the average scores o f the same or similar co m m u n i t y - t y p e( s) in the n at u r al area reserve system.

ACKNOWLEDGEMENTS 1 a m indebted to E d w a r d C. Fritz for leadership in the Texas N a t u r a l A r e a s Survey, to N a n c y Y. G e h l b a c h for ideas o n - a r e a evaluation, and to William E. Tans for constructive c o m m e n t s on a draft o f this paper.

REFERENCES

AULTEATHER,W. & CROZIER,E. S. (1971), A resource inventory and planning system for wildlife areas. J. Wild M g m t , 35, 168-74. DALLAS DEPARTMENTOF PLANNING AND URBAN DEVELOPMENT(1973). The Dallas Ecological Study. FOSBERG, F. R. (1967). A classification of vegetation for general purposes. In Guide to the check sheet for 1BP areas, ed. by G. F. Peterken, 73-120. GEHLBACH,F. R. (1967). Vegetation of the Guadalupe Escarpment, New Mexico-Texas. Ecology, 48, 404-19. GEHLBACH, F. R. (1971). An ecological reflection on cave conservation. In Natural history o f Texas caves, ed. by E. L. Lundelius and B. H. Slaughter, 155-6. Dallas, Gulf Natural History Press. GOLDSM1TB, F. B. (1974). An assessment of the Fosberg and Ellenberg methods of classifying vegetation for conservation purposes. Biol. Conserv., 6, 3-6. JENKINS, R. E. & BEDFORD,W. B. (1973). The use of natural areas to establish environmental baselines. Biol. Conserv., 5, 168-74. LEOPOLD, L. B., CLARKE, F. E., HANSHAW, B. B. t~. BALSLEY,J. R. (1971). A procedure for evaluating environmental impact. Circ. US geol. Surv., 645, 13 pp. LINDSEY, A. A., SCHMELZ,D. V. 8/. NICHOLS, S. A. (1969). Natural areas in Indiana and their preservation. Lafayette, Indiana Natural Areas Survey, 594 pp. MOIR, W. H. (1972). Natural areas. Science, N. Y., 177, 396-400. SHELFORD,V. E. (ed.). (1926). Naturalist's guide to the Americas. Baltimore, Williams and Wilkins Co. SMITH, E. L. (1974). Established natural areas in Arizona. Phoenix, Arizona Planning Div. Office. TANS, W. (1974). Priority ranking of biotic natural areas. Mich. Bot., 13, 31-9. TEXAS NATURALAREASSURVEY(1972). The natural areas o f Texas (preliminary listing). Dallas, Student Council on Pollution and Environment, Environment Protection Agency. Tunas, C. R. & BLACKWOOD,J. W. 0971). Ecological evaluation of land for planning purposes. Biol. Conserv., 3, 169-72. ZIMMERMAN,D. R. (1973). Golden-cheeked warbler: a bird that needs more friends. Natn. Pks Mag., 47, 20-2.