McHarg’s theory and practice of regional ecological planning: retrospect and prospect

Abstract

Ian McHarg’s theory of regional ecological planning is a milestone in the history of planning and socio-ecological practice. The use of science—geology, physiography, soils, hydrology, and vegetation—to determine the appropriate locations for development marked a distinct departure from planning based on promoting economic growth. McHarg tested his theory in practice, most notably in three projects in the USA: The Metropolitan Open Space study of greater Philadelphia, The Plan for the Valleys in Baltimore County, Maryland, and The Woodlands, a new town outside of Houston, Texas. New challenges to regional ecological planning have arisen in the past 30 years: population growth, infrastructure needs, climate change, and social equity and environmental justice. McHarg’s emphasis on the integration of nature and the built environment is still valid, especially in urban/suburban areas, where the use of green infrastructure has gained popularity. McHarg advocated some separation of rural areas from urban/suburban areas to protect farmland and curb sprawl. But more separation is now necessary given America’s much larger and dispersed metropolitan populations. Also, greater emphasis is needed on social equity, environmental justice, and the sustainability of the built environment to provide more affordable housing and to produce more resilient, healthy, walkable, and mixed-use cities and suburbs that rely on mass transit to reduce greenhouse gas emissions.

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Socio-Ecological Practice Research
ISSN 2524-5279
Socio Ecol Pract Res
DOI 10.1007/s42532-019-00024-4
McHarg’s theory and practice of regional
ecological planning: retrospect and prospect
Thomas Daniels

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REVIEW ARTICLE
McHarg’s theory andpractice ofregional ecological planning:
retrospect andprospect
ThomasDaniels1
Received: 18 January 2019 / Accepted: 1 August 2019
© Springer Nature Singapore Pte Ltd. 2019
Abstract
Ian McHarg’s theory of regional ecological planning is a milestone in the history of planning and socio-ecological practice.
The use of science—geology, physiography, soils, hydrology, and vegetation—to determine the appropriate locations for
development marked a distinct departure from planning based on promoting economic growth. McHarg tested his theory in
practice, most notably in three projects in the USA: The Metropolitan Open Space study of greater Philadelphia, The Plan
for the Valleys in Baltimore County, Maryland, and The Woodlands, a new town outside of Houston, Texas. New challenges
to regional ecological planning have arisen in the past 30years: population growth, infrastructure needs, climate change, and
social equity and environmental justice. McHarg’s emphasis on the integration of nature and the built environment is still
valid, especially in urban/suburban areas, where the use of green infrastructure has gained popularity. McHarg advocated
some separation of rural areas from urban/suburban areas to protect farmland and curb sprawl. But more separation is now
necessary given America’s much larger and dispersed metropolitan populations. Also, greater emphasis is needed on social
equity, environmental justice, and the sustainability of the built environment to provide more affordable housing and to
produce more resilient, healthy, walkable, and mixed-use cities and suburbs that rely on mass transit to reduce greenhouse
gas emissions.
Keywords Carrying capacity· Ecological determinism· Plan for the valleys· Regional ecological planning· Socio-
ecological practice· The Woodlands
1 Regional ecological planning
asaresponse tounplanned sprawl
Of the many contributions made by Ian McHarg to our
understanding of ecology, physical design, and land use
planning, his ideas on regional ecological planning have
been the most challenging to implement. The decline of
America’s industrial cities in the 1950s and 1960s often led
to a flight of urban residents to the suburbs, and the suburbs
sprawled across the landscape, turning fields and forests into
shopping malls and housing subdivisions with little regard
for nature (Ammon 2016; Anderson 1965). State and local
governments enacted few laws and land use controls to
control suburban sprawl (Healy and Rosenberg 1979), and
the federal government had yet to adopt the Clean Air Act
(1970) and Clean Water Act Amendments (1972) to regulate
pollution emissions into the nation’s air and water or the
National Environmental Policy Act (NEPA) to review the
environmental impacts of federal projects (Anderson 1973;
Freeman 1990; Portney 1990). This environmental legisla-
tion was aimed at protecting public health rather than pro-
moting good ecological design. The US Environmental Pro-
tection Agency gave no directions on how to build cities or
develop metropolitan regions that would meet air and water
quality regulations and provide a healthy environment (Dan-
iels 2014, p. 667). McHarg wrote his masterpiece, Design
with Nature, to demonstrate how and where to develop sites,
communities, and regions with a sensitivity to the environ-
ment (McHarg 1969, pp. 55–65).
McHarg’s fundamental ideas are: (1) Nature is a process
consisting of physiography, hydrology, drainage, climate,
soil, vegetation, wildlife habitat, and land use (Steiner
2006, p. xiv), and (2) it is desirable to plan and develop
cities and metropolitan regions in concert with natural
* Thomas Daniels
thomasld@design.upenn.edu
1 Department ofCity andRegional Planning, School
ofDesign, University ofPennsylvania, 127 Meyerson Hall,
210 South 34th Street, Philadelphia, PA19104-6311, USA
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Socio-Ecological Practice Research
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features and so maintain ecological processes and services
that benefit both humans and nature (McHarg 1964, p.
24; McHarg 1970, p. 63; Ndubisi 2002, p. 45). This lat-
ter concept became known as “ecological determinism,”
which McHarg tested in practice throughout his career
(McHarg 1966, p. 34). McHarg unified his ideas into a
regional ecological approach to planning and design that
stressed beginning with a scientific inventory and analy-
sis of a region, understanding its suitability and carrying
capacity to accommodate development and then formulat-
ing a plan and implementation techniques for the location
of development and open space (ibid.).
McHarg tested his ideas on regional ecological planning
through practice as a landscape architect and planner. Three
projects in the USA demonstrate the evolution of McHarg’s
thinking and work: (1) The Metropolitan Open Space study
for greater Philadelphia completed in 1963 (McHarg 1963a,
1969, p. 57; University of Pennsylvania 1963); (2) The Plan
for the Valleys in Baltimore County, Maryland, written
with David Wallace in 1964 (Wallace-McHarg Associates
1964); and (3) The Woodlands, a new town 28 miles north
of Houston, Texas in 1974 (Wallace etal. 1974; McHarg
and Sutton 1975). This paper evaluates: (1) the accuracy and
scale of McHarg’s analyses; (2) the implementation of the
drafted plans; (3) the effectiveness of implementation tech-
niques that McHarg proposed and those that have built upon
McHarg’s ideas; and (4) the outcomes of the projects. The
paper then presents new challenges that suggest some further
evolutions of McHarg’s regional ecological planning model.
The Metropolitan Open Space study for greater Philadel-
phia was an early application of regional ecological analysis,
but it did not result in an actual regional plan (McHarg 1969,
p. 65). Today, there is a need for metropolitan regional plans
that address not only ecological issues, but the infrastructure
of the built environment and social issues of environmen-
tal justice and affordable housing. The Plan for the Valleys
was a sub-regional analysis and plan for locating a large
amount of development amid a sub-region of 44,000 acres
of mostly open land, but the plan was not implemented (Avin
2013, pp. 21–22; Bunster-Ossa 2014, p. 7; Ndubisi 2002, p.
47). The plan raised issues about the degree to which urban
development can be integrated within a rural environment
(Hundt Jr. and Daniels 2018, p. 15). The plan did lead to
a strong growth management effort in Baltimore County,
Maryland, featuring the separation of rural and urban areas
to control sprawl. And controlling sprawl remains a major
challenge for metro areas today (Burge etal. 2013, p. 235).
The Woodlands was another sub-regional analysis and large
site planning exercise on 29,000 acres. Here, McHarg was
successful in fitting development within the constraints and
opportunities of the environment (McHarg etal. 1979, p.
262). However, further development of The Woodlands did
not reflect McHarg’s ecological principles and exceeded the
carrying capacity of the area (Yang etal. 2015, pp. 781, 784;
Yang 2019).
2 McHarg’s theory ofregional ecological
planning
Ecology is the science of the interaction between organisms
(including humans) and their environment (Odum 1997).
McHarg devised his theory of regional ecological planning,
which he called ecological determinism, as a science-based
settlement strategy to counter the prevailing model of plan-
ning as promoter of real estate development and economic
growth (Ndubisi 2002, p. 45; Daniels etal. 2007, p. xxviii).
McHarg’s regional ecological theory explains how to meas-
ure the overall health of a region; how to assess the region’s
ecological constraints and opportunities for development,
and how to identify scientifically the degree of suitability
of large and small sites for development (see Table1). To
McHarg, the basic problem of regional ecological planning
is to determine the place of humans in nature. This approach
predicts that if development respects the natural processes
and limitations of the landscape, then development can
occur in harmony with nature, to the benefit of both humans
and nature. However, if development degrades or destroys
natural processes, then the overall health of the region will
decline (McHarg1967, 1969, p. 65).
Ecological determinism begins with a survey of the
region’s environmental features based on the combined sci-
ences of geology, physiography, hydrology, soils, vegetation,
wildlife habitats, mineral resources, and climate. These sci-
ences provide a “layer cake” of data about a region, leading
to a mapping overlay exercise to determine opportunities
and constraints for development (McHarg 1981, p. 96; Her-
rington 2010, p. 4). McHarg identified eight natural land-
scape features from the least to the most suitable for devel-
opment in an ecological region (see Table2). “Planning,”
McHarg opined. “Should recognize the values of these
[natural] processes in decision-making for prospective land
uses” (McHarg 1964, p. 24). Yet, McHarg also recognized
the human element of rules and regulations that influence
Table 1 McHarg’s six steps in ecological determinism. Source:
McHarg (1966, p. 34)
Steps
1. Ecosystem inventory
2. Description of natural processes
3. Identification of limiting factors (water, slope, soils, etc)
4. Attribution of value (i.e., ecological services)
5. Determination of prohibitions and permissiveness to change
6. Identification of indicators of stability or instability
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land use change and the importance to planning efforts
of indicators of ecological stability in a region. McHarg
hypothesized, “If the process is successful, the constituen-
cies will select the fittest environments, adapting these and
themselves to achieve a creative fitting” (McHarg 1978,
p. 89; McHarg, 2007). Thus, sound scientific information
could enable planners to determine the suitability of sites
for development or open space. This information would also
guide planners in drafting regional plans for a harmonious
and healthy integration of development, nature, and natural
processes. That was the hypothesis that needed to be tested.
3 The open space study formetropolitan
Philadelphia
McHarg tested his theory of regional ecological planning
through on-the-ground projects. For each project evaluated
in this paper, I assess the regional ecological analysis, the
subsequent plan, implementation techniques that emerged
from McHarg’s ideas, and the outcomes and challenges that
suggest some revision to McHarg’s regional ecological plan-
ning model.
3.1 Regional ecological analysis
In 1963, McHarg was the principal investigator for a study
of open lands in an eight-county region of greater Philadel-
phia (McHarg 1963b; University of Pennsylvania 1963). The
study began with the premise that there were two kinds of
open lands: those that performed work for humans without
any investment, such as wetlands, and those that were haz-
ardous and posed threats to property and human safety. To
identify suitability for development, McHarg chose eight
types of natural land, from the least to the most suitable (see
Table2) and defined a metro area as a region about 30 miles
across as in the case of greater Philadelphia’s eight counties
of Bucks, Chester, Delaware, Montgomery, and Philadelphia
in Pennsylvania, and Burlington, Camden, and Gloucester in
New Jersey (see Fig.1).
McHarg expected that the form of regional development
integrated with natural areas would emerge organically: “If
growth responds to natural processes, it will be clearly visi-
ble in the pattern and distribution of development” (McHarg,
1969, p. 161). That was the hypothesis. McHarg rejected the
idea of simply creating a greenbelt–what today would be
called a growth boundary—to fully separate natural areas
from developed areas (ibid., p. 56). McHarg’s approach was
to attempt to integrate development and natural areas. Yet,
in retrospect, McHarg admitted that in testing his hypothesis
“concentration on open space alone reduced the scope of
the Philadelphia metropolitan study,” because the study did
not focus as much on development needs for land (McHarg
1969, p. 127; Ndubisi 2002, p. 29).
Measuring open space without the benefit of GIS or
remote sensing proved difficult. For example, in the case of
Table 2 Eight natural landscape features, from least to most suitable
for development. Source: McHarg (1969, p. 57)
1. Surface water 5. Aquifers
2. Marshes 6. Steep slopes
3. Flood plains 7. Forests and woodlands
4. Aquifer recharge areas 8. Flat land
Fig. 1 The eight-County stand-
ard metropolitan statistical area
of greater Philadelphia, 1960
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agricultural land, McHarg and his team identified 11.7% of
the region as agricultural land in 1963, which was far less
than the 35 percent of the land base (808,000 acres) listed
as agricultural land in the 1964 Census of Agriculture (U.S.
Census Bureau 1964). The 1964 Census showed a total of
18.4% of the region as harvested cropland, the land easiest
to develop as well as the most productive farmland (ibid.).
The technology of landscape analysis has much improved
in recent decades, enabling a fine-grained understanding of
individual sites, landscape patches, and regional ecological
systems (Ndubisi 2002, p. 28; Steiner 2017, p. 83).
3.2 Regional ecological principles rather
thanaplan
McHarg and his team did not propose a specific plan for
greater Philadelphia, and hence no implementation tech-
niques were recommended or tested. Instead, their analysis
of the region offered a set of principles that McHarg and
others would draw on in future work. McHarg approached
metropolitan regional planning with a recognition of its limi-
tations, stating, “[T]he metropolitan area occupies an area
of land but constitutes the sum of many levels and forms of
government. It is united neither by government, planning,
nor an expression of these” (McHarg 1969, p. 153). Moreo-
ver, at the time, there was no ecological model of metro-
politan areas. To try to overcome these limitations, McHarg
called for a simple, yet powerful guiding principle: “certain
lands are unsuitable for urbanization and others are intrin-
sically suitable” (ibid., p. 154). But in a region without a
regional government, it was not realistic to expect hundreds
of local governments to conduct analyses of development
suitability. McHarg believed that “[a] structure for metro-
politan growth can be combined with a network of open
spaces that not only protects natural processes but also is
of inestimable value for amenity and recreation” (McHarg
1970, p. 64). But to achieve that outcome would require a
metropolitan regional government.
3.3 Outcomes forgreater Philadelphia
The 1963 Metropolitan Open Space study without an accom-
panying plan was of little benefit to greater Philadelphia.
Governance appears to be one of the major obstacles to an
ecological plan for the region. For instance, although the
Delaware Valley Regional Planning Commission has drafted
regional land use plans, these plans are advisory. As David
Rusk has pointed out, the greater the number of local gov-
ernments, the more sprawl is likely to occur because of
the hunt for property tax ratables (Rusk 1993, 2010). This
hunt creates a bias in favor of development as opposed to
ecological planning. Philadelphia is one of the most frag-
mented metro regions in the USA in terms of the number
of local governments. Within the eight-county region, there
are nearly 340 townships, cities, and boroughs (villages),
each with control over planning and zoning (DVRPC 2018).
One indication of the loss of open space in the region
since McHarg’s 1963 study is that by 2017, the amount of
farmland had fallen by nearly half to 410,616 acres (USDA
2019). In the greater Philadelphia region, the eight coun-
ties had a total population of 4,342,897 in 1960. By 2010,
the population was 5,259,684, an increase of 21%. Phila-
delphia County lost nearly 500,000 residents during these
50years. The settlement pattern for the region was more
dispersed in 2010 than in 1963 with Bucks, Burlington,
Chester, Gloucester Counties more than doubling in pop-
ulation between 1960 and 2010 and Montgomery County
adding more than 250,000 residents (U.S. Census Bureau
1970, 2018a, b).
3.4 Re‑assessing McHarg’s greater Philadelphia
study
The experience of greater Philadelphia over the past 55years
suggests the limitations of analyzing the land capability
of the region to support development without tying that
analysis to a regional plan and specific implementation
techniques. Public planning and zoning have largely been
ineffective in maintaining open space in the Philadelphia
metropolitan region, in keeping with McHarg’s criticism
that “present land use regulations do not recognize natural
processes; the public benefits of environmental services and
do not place responsibility on landowners and developers”
(McHarg 1970, p. 83).
The settlement pattern of the “exploding metropolis” for
greater Philadelphia and other metro areas has put envi-
ronmental strain on a much greater geographic area and
increased demands on rural lands for water and recreation
(Daniels 1998; Demographia 2014). Limiting the spread of
urban and suburban development into the countryside has
become a higher priority than in the 1963 study (Chapin
2012; Daniels 2001, 2014). McHarg’s primary approach was
to try to integrate nature and development through the suit-
ability analysis process (Ndubisi 2002, p. 44; Bunster-Ossa
2014, p. 4).
One critic has even contended that McHarg’s suitability
analysis facilitated the spread of suburbia across the Ameri-
can landscape (Bunster-Ossa 2014, p. xiv). But this criticism
is misplaced. McHarg noted that for suburbs “the instinct
to find more natural environments became the impulse that
destroyed nature” (McHarg 1969, p. 154). But many other
factors were also at work in greater Philadelphia. Population
growth, the decline of manufacturing, the inability of the
city to expand in size, racial and income divisions, cheap and
plentiful energy, highway construction, abundant housing
finance, and the fragmented local government structure led
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to the expansion of the suburbs (Gillham 2002, pp. 36–46;
Jackson 1985; Rusk 1993, 2010; Squires 2002, p. 2). Also,
suburban zoning that encourages commercial and residential
development has played an important role in the expansion
of metropolitan regions (Rusk 1993; Duany etal., 2000). In
short, growth and development did not respond to natural
processes as McHarg had predicted.
In sum, the Philadelphia Metropolitan Open Space study
enabled McHarg to test his ideas about regional ecological
analysis, but mainly from an academic approach. There was
no clear plan, settlement strategy, or set of implementation
techniques that resulted from the study. The drafting of a
plan would come a year later in the famous Plan for the
Valleys.
4 Regional ecological analysis andplanning:
thePlan forthevalleys
The Metropolitan Open Space study laid the foundation for
McHarg’s work with David Wallace on The Plan for the
Valleys, in Baltimore County, Maryland in 1964 (Wallace-
McHarg Associates 1964a, b). The interstate highways had
recently been completed, placing the three valleys of north-
western Baltimore County within easy commuting distance
of the City of Baltimore. A group of private landowners
hired McHarg and David Wallace, a planning professor from
the University of Pennsylvania, to conduct a plan for the
future growth and development of the three valleys with the
hope of avoiding haphazard sprawl (Hundt Jr. and Daniels
2018, p. 7).
4.1 Regional ecological analysis ofthethree valleys
The Plan for the Valleys drew on the general regional eco-
logical analysis experience from the Metropolitan Open
Space study for greater Philadelphia to understand where
development would have the best fit. McHarg then added a
more fine-grained analysis, based on a layer cake of scien-
tific data about development suitability (Avin 2013; Hundt
Jr. and Daniels 2018, p. 7; Wallace-McHarg Associates
1964a, b). It became clear that the valley floors should not
be developed because of the sensitive hydrology and because
they contained the best soils for agricultural production.
McHarg and Wallace identified the hilly plateaus as the most
appropriate sites for development. But how much develop-
ment could the region absorb?
4.2 The plan andimplementation techniques
McHarg and Wallace melded the regional ecological analy-
sis and physiographic determinism together with population
growth projections, and optimum development levels. The
plan attempted to avoid uncontrolled growth and save on
infrastructure costs in supporting new development (McHarg
and Wallace 1965). The plan attempted to integrate 26,000
dwellings into a rural landscape (Bunster-Ossa 2014, p. 7)
(see Fig.2). The population of the valleys was projected
to increase substantially from 17,000 to 110,000 or more
residents.
To protect the valley floors, the plan recommended three
techniques: a growth boundary to limit the extension of
sewer and waterlines, low-density zoning, and a conserva-
tion area where conservation easements would be acquired
to keep the land undeveloped (Hundt Jr. and Daniels 2018,
p. 11). McHarg envisioned the creation of a syndicate of
landowners to acquire what today would be called Trans-
ferable Development Rights (TDRs) to compensate valley
landowners for not developing their property and moving the
development potential to the plateaus (ibid.). However, the
syndicate proved too complicated to implement.
4.3 Outcomes andchallenges forthevalleys
The development of the proposed new settlements never
happened; the local residents simply did not want that much
development. Even though McHarg and Wallace proposed to
locate the development on the hilly plateaus, away from the
mostly agricultural valley floors, the local residents feared
that if sewer lines were extended to the developments on the
Fig. 2 The basic amenity of the valleys: the valley floors and the for-
ested walls. Source: Wallace-McHarg Associates The Plan for the
Valleys (1964b). Credit: Ian L. McHarg Papers, The Architectural
Archives, University of Pennsylvania
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plateaus that the valley floors would also become sewered
and developed.
As in the case of greater Philadelphia, McHarg was
attempting to integrate development and open lands. A les-
son from The Plan for the Valleys is that separating devel-
opment and nature is sometimes desirable and justifiable
(Hundt Jr. and Daniels 2018, p. 15). Also, a key issue that
continues to arise is: what is the compatibility of develop-
ment and the local or regional ecology?
Baltimore County responded to The Plan for the Valleys
in 1967 by adopting its famous Urban–Rural Demarcation
Line, a growth boundary separating urban and suburban
development from the rural areas. This was the second
growth boundary adopted in the USA, after Lexington-Fay-
ette County, Kentucky in 1958 (ibid.).
Starting in 1976, Baltimore County implemented very
low-density Resource Conservation (RC) Zoning which
now protects more than 135,000 acres of farmland. Since
1975, landowners in the County have preserved more than
64,000 acres of farmland and natural lands through the sale
or donation of conservation easements (Baltimore County
2018, p. 1).
The combination of growth boundaries, natural resource
zoning, and the acquisition of conservation easements has
enabled Baltimore County to maintain an agricultural indus-
try generating $67 million a year in sales within a metro-
politan region (USDA 2019). This combination of growth
controls has also become a hallmark of some of the nation’s
leading counties in growth management, including Lan-
caster County, Pennsylvania; Lexington–Fayette County,
Kentucky; and Sonoma County, California (Hundt Jr. and
Daniels 2018, p. 11).
Of the three valleys, the Green Spring Valley has experi-
enced a considerable amount of scattered residential devel-
opment on large lots; yet, the Caves and Worthington Valleys
are still much the same thanks to low-density zoning and
the decisions of many farmland owners to sell or donate
conservation easements on their land (ibid.). Moreover, an
estimated 90 percent of the county’s population lives inside
the URDL, on about one-third of the county land area (ibid.).
4.4 Re‑assessing thePlan fortheValleys
The regional ecological analysis of The Plan for the Valleys
shows an accurate evaluation of the appropriate location of
development. The question arises here and in The Wood-
lands of how much development is ecologically sustainable
as well as politically acceptable.
The Plan for the Valleys was not a true metro-regional
plan. McHarg himself admitted that “the study of the Val-
leys existed in only a part of a metropolitan and physi-
ographic region” (McHarg 1969, p. 127). Yet, writing in
1996, McHarg proudly noted that the Valleys “more than
30years later still retain their pastoral beauty” (McHarg
1996, p. 177).
5 Regional ecological planning inanew
town: The Woodlands
McHarg sought to integrate nature into development in his
practice as a landscape architect, perhaps most notably at
The Woodlands, a project he considered “the best exam-
ple of ecologically based new town planning in the United
States during the 1970s” (McHarg 1996, p. 325). The site
covers 29,000 acres in the coastal plain mostly in Harris and
Montgomery Counties, 28 miles north-northwest of Hou-
ston, Texas. The property was owned by George Mitchell, a
successful oil and gas developer, and a pioneer of hydraulic
fracturing. Mitchell wanted to build a master-planned new
town of 180,000 residents that would fit in with the environ-
ment (Malone 1985). The new town would have commercial,
industrial, and recreational developments along with thou-
sands of homes and miles of roads. Mitchell hoped that the
City of Houston would eventually annex The Woodlands
into the city, but that never happened (ibid.).
5.1 Regional ecological analysis ofThe Woodlands
Whereas the Metropolitan Open Space study for greater
Philadelphia was a broad overview of the region’s natural
areas, The Woodlands required a fine-grained analysis of the
natural environment to determine where to clear land, where
to build, and what lands to maintain in their natural condi-
tion (Wallace etal. 1973, 1974; McHarg and Sutton 1975)
(See Fig.3). Because of a HUD loan that partially funded
the project, The Woodlands had to undergo the Environ-
mental Impact Statement process, one of the first under the
National Environmental Policy Act of 1970, and the studies
by WMRT served as the impact statement (Yang etal. 2015,
p. 776).
McHarg focused on the hydrology of the site (Forsyth
2003, p. 12; McHarg and Sutton 1975). He was quick to
note that The Woodlands had several constraints. Impervi-
ous soils covered about one-third of the area. The land was
generally flat, drainage was slow, and there was standing
water. The forests and wildlife habitat would be needed both
to help absorb stormwater runoff and enable the water to
move rather than pond up; and development would have to
avoid the 100-year floodplains which buffered the streams
and covered about one-third of the site (Forsyth 2003, p. 12).
5.2 The plan andimplementation techniques
The plan for The Woodlands featured development design
(McHarg and Sutton 1975). Unlike the Plan for the Valleys,
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there was no mention of land preservation or zoning. The
design strategy was to keep development away from the
highly permeable soils, retain as much forest as possible,
and integrate open space for surface drainage (Yang etal.
2015, pp. 777–778). The opportunities were to place high-
density development on the impervious soils, clear pine trees
instead of hardwoods, which were less tolerant of distur-
bance, and match proposed development types and densities
with appropriate locations (McHarg etal. 1979, p. 257). A
financial benefit of the design of The Woodlands was that
it avoided expensive engineering projects by emphasizing
compatibility with nature (Forsyth 2003, p. 12).
5.3 The Woodlands plan andoutcomes
The Woodlands was launched in 1974 in part with help from
a $50 million HUD New Communities loan (Forsyth 2003,
p. 11, 2005; Yang etal. 2015, p. 774). By 1979, there were
2,500 residents. Ownership of The Woodlands development
company changed hands three times as the population grew
to 93,847 in 2010. The following year, the Howard Hughes
Development Corporation purchased The Woodlands and
began additional development. In 2017, before the arrival
of Hurricane Harvey, there were an estimated 114,625 resi-
dents. As of 2018, The Woodlands boasted 215 miles of
hike and bike trails, 146 parks, 7790 acres of green space
(over one-quarter of the new town), 10 villages, and some
500 acres of office, institutional, and industrial space (The
Woodlands 2018).
Residents of The Woodlands are heavily dependent on
cars for transportation in part because of the low-density
design and large percentage of single-family detached
housing (Forsyth 2003, p. 13). Transportation networks are
largely overlooked in McHarg’s regional ecological planning
approach (University of Pennsylvania 1963; McHarg and
Wallace 1965; McHarg and Sutton 1975). Today, suburban
and ex-urban development residents rely primarily on cars,
and motor vehicles are a leading source of America’s green-
houses gases and air pollution in many metro areas (Daniels
2014, p. 535). The increasing population and the less green
development after 1997 in The Woodlands have coincided
with the explosive, sprawling growth of greater Houston
(Forsyth 2003, p. 13; Yang and Li 2011; Yang etal. 2015,
pp. 781, 784). For instance, between 1996 and 2001, the
developed area of The Woodlands increased by 3500 acres
and the forest shrank by more than 4000 acres; the newer
development did not follow McHarg’s design with nature
principles (Yang etal., 2015, p. 784; Yang 2019).
When Hurricane Harvey struck the greater Houston
region in late August of 2017, it brought a record amount
of rainfall. Up to 50 inches of rain fell on parts of greater
Houston, causing widespread flooding, taking more than
50 lives, inundating 204,000 homes, and wreaking an
estimated $125 billion in damage. The New York Times
reported that in The Woodlands “recently constructed neigh-
borhoods flooded at far higher rates than others” (Schwartz
etal. 2017, p. 8). Among the older homes, about 215 out of
33,000 homes were flooded, a rate of less than one percent,
whereas 331 out of 1450 new homes, or 23 percent, were
flooded (ibid.).
5.4 Re‑assessing The Woodlands
The regional ecological design proposed by Wallace,
McHarg, Roberts, and Todd withstood the brutal test of
Harvey. Their design also underscored the fragility and
Fig. 3 The elevated design for
road and house sites on pervious
soils in the Woodlands. Source:
Wallace etal. (1973, p. 7)
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Socio-Ecological Practice Research
1 3
limitations of The Woodlands to accommodate an ever-
increasing number of residents. Although the original
design led to a financially successful project, the addi-
tion of more dwellings to The Woodlands after 1996 was
bound to occur on less environmentally suitable land
(Yang etal. 2015, p. 784). This tension between the real
estate profit motive and the ecological fitness of develop-
ment will continue so long as new developments are being
built. When the two goals are compatible, then develop-
ment can be beneficial. When they are not compatible,
either a profitable development cannot be built, or the
development will be especially vulnerable to natural haz-
ards. Those outcomes are what McHarg had predicted
from this regional ecological theory. Yet, few new towns
on the scale and with the ecological sensitivity of The
Woodlands appear possible (ibid.).
6 Current planning challenges andrevisions
toMcHarg’s regional planning model
Current planning challenges present obstacles to imple-
menting McHarg’s regional ecological planning prin-
ciples. They are also broader in scope than McHarg’s
focus on ecology and require some revisions to McHarg’s
model. The first challenge includes population growth,
the growth of metro regions, and the location of develop-
ment within those regions. In response, greater integra-
tion of nature in cities and suburbs will be needed to: (1)
remediate the built environment; (2) enable an increase
in the density of development; (3) make new development
more resilient to natural disasters; and, (4) reduce the
emphasis on greenfield development.
A second challenge is that the separation of rural and
urban areas is needed to minimize sprawl; attempts to
integrate urban development with rural lands have gen-
erally led to sprawl and the loss of rural lands. A third
challenge is the lack of regional governments which
has undercut the effectiveness of regional plans and the
implementation of regional ecological planning. A fourth
challenge is climate change from greenhouse gas emis-
sions generated by humans now poses serious threats to a
region’s natural environment and built environment, and
to nature on earth (Steiner 2017, p. 81). Adapting to the
effects of climate change with the help of green infra-
structure will be needed as well as more careful invest-
ment in the built environment. Finally, social issues, such
as equity, environmental justice, and affordable housing
have become as important as environmental and economic
issues in the triple bottom line of sustainability (Bunster-
Ossa 2014, pp. 33, 35).
6.1 Population growth andthedominance
ofmetropolitan regions
Population levels and population growth affect the carrying
capacity of a region to support development without major
negative environmental impacts. There are now 328 million
Americans, an increase of more than 100 million compared
to when McHarg conducted his regional planning work in
the 1960s and 1970s. The stresses on natural resources are
much greater today because of the larger population and
the effects of climate change (Daniels 2014, p. 661; Steiner
2017, p. 81). The looming challenge is how to accommo-
date a projected 70 million additional Americans by 2051
(Colby and Ortman 2015, p. 1). While McHarg recognized
the urgency of regional ecological planning, the sheer scale
and urgency of regional planning work have only become
more critical.
Much of McHarg’s regional work involved where to put
development on greenfield sites, such as in The Plan for the
Valleys and The Woodlands (Ndubisi 2002, pp. 47, 75–76).
Writing later in life, McHarg noted that how and where
to integrate nature and the built environment remained a
challenge: “We observed that the greatest problem lies not
with data, but with integration” (McHarg 1996, p. 363).
A key factor in that integration is adequate infrastructure,
and McHarg tends to overlook the cost and development-
inducing effects of transportation and central sewer and
water systems (McHarg 1968; McHarg and Sutton 1975).
Infrastructure has become very expensive in accessing new
areas for development. When cities and suburbs push into
the countryside, mass transit systems are slow to expand.
The preferred mode of transportation is cars and trucks,
which means road construction and road widenings. In his
study of where to locate highways, McHarg did not make
the connection to greenhouse gas emissions, which are of
critical concern today (IPCC 2018; McHarg 1968). In the
Plan for the Valleys, the local residents did not embrace the
proposal for large developments on the plateaus because they
feared the extension of sewer and water lines would lead to
the development of the valley floors (Hundt Jr. and Daniels,
2018, p. 10).
To accommodate tens of millions more Americans and
to reduce greenhouse gas emissions, development must be
concentrated on reviving cities, infill development, and the
adaptive re-use of urban and suburban sites and buildings
(Calthorpe 2010). McHarg’s concept of integrating nature
and the built environment has value in helping to revital-
ize cities and densify suburbs, rather than aiding the fur-
ther expansion of metro areas. Planners and designers have
promoted green infrastructure from the site-specific to the
regional scale to reduce stormwater runoff—a major source
of water pollution, mitigate the urban heat island effect,
provide recreation opportunities, connect wildlife hubs and
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Socio-Ecological Practice Research
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migration corridors, and to guard against natural hazards,
such as flooding and storm surges (Benedict and McMahon
2006; Daniels 2014, pp. 29–31). In sum, the installation and
maintenance of green infrastructure in existing cities and
suburbs will need to become the primary application of a
design with nature approach.
6.2 Separating urban andrural areas
The difficulty in integrating urban and rural land uses is
well-documented. The loss of farmland to urban develop-
ment has been a national concern for almost 40years (NALS
1981). Millions of people who live in the wildlands–urban
interface in the west are at a high risk of exposure to forest
fires (Theobald and Romme 2007, p. 352). And the primary
cause of wildlife decline is the loss of habitat to human
development (Daniels 2014, p. 308).
If cities and suburbs are to accommodate more people,
then protecting the countryside from sprawling develop-
ment will take on greater importance. Peter Calthorpe and
William Fulton put forth the idea that the city is now the
region (Calthorpe and Fulton 2001). The challenge is to
design the regional city for human scale by combining a
pleasant, efficient, and relatively dense built environment
with green space. But inherent in the regional city concept is
the existence of a growth boundary, separating the city from
the countryside, rather than attempting to integrate the city
and the countryside.
McHarg, however, rejected the greenbelt or growth
boundary approach to rural land protection and metropolitan
planning (McHarg 1969, p. 56). Even so, growth boundaries
that separate urban from rural land have become popular on
the West Coast (California, Oregon, and Washington) and
examples exist in the South (Florida and Tennessee) and the
Mid-Atlantic states (Pennsylvania and Virginia). A growth
boundary can promote a compact, relatively dense devel-
opment pattern, and an increase in the use of mass transit,
walking, and biking, which help to reduce greenhouse gas
emissions (Nelson etal. 2004). Implementing greenbelts/
growth boundaries to separate urban and rural areas is a
good application of designing with nature.
6.3 The lack ofregional governments andregional
ecological planning inpractice
Metropolitan regions now contain four-fifths of America’s
population and most Americans live in suburbs (Frey 2012).
However, the USA has few, if any, examples of regional
ecological plans that have been implemented at the metro-
politan level. A primary reason is that there are very few
regional governments with the power to plan and zone land.
Even Metro of greater Portland, Oregon, the nation’s only
elected regional government, must balance its planning with
those of three counties and 24 municipalities (Metro 2018).
Metropolitan regions consist of dozens, if not hundreds of
local governments, each with control over planning and zon-
ing. Coordinating local planning into a metropolitan regional
plan has proven elusive.
Much of the metropolitan planning today is remedial
and reactive in regions that are largely built-out, rather than
proactive planning and designing for mostly undeveloped
sub-regions as in the Plan for the Valleys and The Wood-
lands. More than 300 Metropolitan Planning Organizations
(MPOs) are limited to transportation planning and have no
zoning powers. Similarly, regional planning commissions
in metro areas (nearly all of which also serve as the region’s
MPO) can draft regional plans, but these plans are advisory
and the regional planning commissions do not have zoning
powers to implement their plans (Seymour 2011, p. 227).
McHarg pointed out that traditional land use planning did
not integrate the limitations and services of nature and as a
result traditional planning resulted in sprawl and ugly devel-
opment that destroyed nature (McHarg 1970, p. 83). But
McHarg did not fully appreciate that to draft and implement
a metro-regional ecological plan requires a regional gov-
ernment. Metropolitan regional governments did not exist
and still do not exist in greater Philadelphia, Baltimore, or
Houston. Metro-regional comprehensive plans with a strong
ecological element are needed. To implement these plans
will require such measures such as urban growth boundaries
to enforce compact development, restrictive zoning, and land
preservation in the countryside to limit sprawl; inside the
growth boundaries, there must be adequate infrastructure,
density, and a mix of land uses and greenspace to accom-
modate the large majority of new development (Calthorpe
2010).
6.4 The challenge ofclimate change
To place McHarg in his historical context, it is important
to note that climate change has become the leading envi-
ronmental issue only within the past 20years, well after
McHarg formulated his theory of regional ecological plan-
ning (Calthorpe 2010). In 2018, the Intergovernmental Panel
on Climate Change (IPCC) reported that the world has only
12years in which to reduce greenhouse gas emissions to
keep global temperatures from rising less than 1.5°C since
the start of the Industrial Revolution (IPCC 2018). Climate
change and greenhouse gas emissions from the burning of
fossil fuels were not prominent issues for regional ecological
planning in the 1960s and 1970s.
Compact urban and suburban development that can be
serviced by mass transit, walking, and bicycling options can
help to reduce greenhouse gas emissions (Calthorpe 2010).
Separating urban and suburban areas from rural areas will
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limit sprawl, vehicle miles traveled, and greenhouse gas
emissions.
The concept of design with nature has taken on added
urgency because of the threats posed by climate change: sea
level rise, more frequent and intense storms, rising average
temperatures, more frequent and larger wildfires, arid places
experiencing prolonged drought, and humid places experi-
encing more intense rain events. The need to adapt to climate
change is clear (ibid.). Engineered interventions, such as
building levees and sea walls, are hugely expensive, do not
work with nature, and are not long-term solutions. Identify-
ing areas vulnerable to climate change-induced disasters and
directing development away from those areas is essential.
For example, McHarg identified the coastal plain as an area
suitable only for limited development (McHarg 1969, pp.
7–17); this is a region where development is already becom-
ing increasingly vulnerable. Maintaining natural features
such as floodplains, dunes, and marshes will help to absorb
rising sea levels, flood waters, and storm surges, thus protect
human health and safety.
6.5 Social issues
Social issues hold great importance as part of the triple
bottom line of sustainability; these include environmental
justice, social equity, and affordable housing. Yet, McHarg
was known for a lack of interest in social issues (Herrington
2010, p. 8). As America continues to add population, deci-
sions about siting locally unwanted land uses, the protection
of vulnerable developments, and the provision of affordable
housing will be paramount, especially for lower income
communities within a metro region. Since Design with
Nature was published, America has grown by more than 120
million people, and land has become scarcer as measured
by the increase in inflation-adjusted real estate prices (US
Census Bureau and US Department of Housing and Urban
Development 2019). Access to safe and affordable housing
continues to be a fundamental need. Moreover, environmen-
tal justice, the right to a safe and healthy environment for
an increasingly diverse population, is an issue that did not
gain prominence until after McHarg left the academic world
(Bullard etal. 2001). Regional ecological planning must be
married to environmental justice if such planning is to reflect
maximum public benefit.
7 The evolution ofMcHarg’s regional
ecological model
Ian McHarg’s theory of regional ecological planning
evolved from a Metropolitan Open Space study for greater
Philadelphia to a plan for a sub-region of Baltimore
County to a plan and built design in The Woodlands new
town in Texas. The theory has stood the test of time in on-
the-ground practice but requires some adjustment to meet
new and broader planning challenges. Regional ecological
analysis has become the basis for several county compre-
hensive plans and large-scale master-planned communities
but has not resulted in metropolitan regional ecological
plans. McHarg’s layer cake ecological analysis underlies a
widespread green infrastructure movement in urban plan-
ning and design and has spurred the application of innova-
tive planning and design techniques to protect open lands
and better integrate the natural environment and the built
environment.
The lack of metropolitan regional governments has hin-
dered the application of regional ecological planning. Met-
ropolitan regional plans are mainly limited to MPO trans-
portation plans and the advisory plans of regional planning
agencies, and the agencies do not have control over zoning to
implement those plans. Metropolitan regions, such as greater
Philadelphia, are an amalgam of dozens if not hundreds
of municipal governments, many of which are motivated
toward the expansion of the property tax base through devel-
opment, rather than the protection of natural areas and open
space. Sub-regional planning, such as at The Woodlands and
The Valleys in Baltimore County, appears easier to do.
The integration of the built environment and green infra-
structure must concentrate on making existing cities and
suburbs denser and more sustainable to adapt to climate
change. The separation of cities and suburbs from rural areas
is needed to reinforce compact development and to limit
the emission of greenhouse gases. Yet, population growth
poses a threat to environmental carrying capacity. Since
Design with Nature appeared in 1969, America has added
more than 120 million people to reach 328 million. Envi-
ronmental impacts increase along with population growth.
This is one of the lessons of The Woodlands. The new town
became more vulnerable as less environmentally fit lands
were developed after 1997 (Yang etal. 2015, p. 781; Yang
2019). And then Hurricane Harvey struck. The older, better
situated homes suffered much less flooding.
Today, the model of the triple bottom line of social, eco-
nomic, and environmental sustainability gives equal weight
to these concerns. The McHarg regional ecological model
must also be consistent with the social goals of environmen-
tal justice and equity and economic goals of the efficient use
of resources and cost-effective infrastructure.
Finally, one of the most valuable ingredients that McHarg
added to the planning process was a sense of urgency. He
wrote, “Can we hope that man[kind] will be able to change
the physical environment to create a new ecology in which
he is a primary agent, but which will be a self-perpetuating
and not a retrogressive process?” (McHarg 1963a, b, p. 7).
That urgency for sustainable regional ecological planning
has only increased and will continue to do so.
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Thomas Daniels is a professor in
the Department of City and
Regional Planning at the Univer-
sity of Pennsylvania where he
teaches Land Use Planning,
Environmental Planning, and
Growth Management. His
research interests include farm-
land preservation, green infra-
structure, and climate change.
Author's personal copy