2000 CRC Press LLC

CHAPTER 5

Principles and Practices

of Ecological Restoration

Introduction

Restoration as a general term means returning

some degraded portion of landscape to an improved

and more natural preexisting condition. It

means reestablishing a healthy ecosystem which

Aldo Leopold (1949) defined as “the capacity of

the land for self-renewal.” John Berger (1990),

author of Restoring the Earth, called restoration

“an effort to imitate nature in all its artistry and

complexity by taking a degraded system and making

it more diverse and productive.”It can involve

the reestablishment of an ecosystem, the control of

air pollution, the prevention of acid rain, or the

protection of habitat for animals where they nest,

rest, and spend the winter. Restoration can mean

making something grow on bare soil or on damaged,

inverted soils (e.g., mine spoil). Restoration

also means replanting a forest in a field. Sometimes

it is the practice of an art (things work for reasons

not known) and sometimes it is science (things

work and we know why). Because this book deals

broadly with the restoration of landscapes and

managed lands, we decided to use the term ecological

restoration to mean returning a specific area to

its predisturbance condition, including both functional

and structural characteristics. In reality, some

of the projects and goals outlined in this book are

habitat creations. The uncertainty about the extent

and composition of the original community may

make habitat creation both practical and necessary

for overall ecological restoration. In the limited

areas available for golf course construction, for

example, restoration of a hydrologically altered

wetland may not be possible, but creation of a fully

functioning marsh or swamp may be possible and

desirable.

What is the difference between ecological restoration

and natural landscaping? To some extent, restoration

encompasses all plantings designed to improve

a site. Natural landscaping can be considered a

form of restoration. For the purposes of this book,

ecological restoration is distinquished from natural

landscaping. If the goal is to restore a native plant

community and a complement of native species from

that community has been used in a planting scheme,

then it is ecological restoration. Natural landscaping is

the planting of a group of native species to meet some

specific aesthetic, management, or design goals. There

is generally a difference of intent and scale between

these two actions. Ecological restoration is large and

allows a community to evolve and natural succession

to occur. Natural landscaping is conducted on a

smaller scale and tends to remain at a particular

managed level or state.

The natural world without human intervention

is the cumulative, dynamic response to millions of

years of reacting to itself and the physical world

around it. Humans do not understand all of the

intricacies of ecosystems. We channelize a stream

to drain a wetland and, in the simplicity of our

desires and understanding, destroy what the wetland

is to the stream—a source of water in summer,

a filter of chemicals and sediment, a refuge for

young fish, and a sponge to soak up and hold heavy

rains. Destroying the results of millions of years of

nature’s work is infinitely easier than restoring it.

Ecological restoration is the art and science of

recreating viable natural or ecological communities.

It goes beyond just doing plantings for the

purpose of stabilizing areas that are eroding. It goes

beyond the idea of landscaping with native plants.

It is an attempt to recreate nature. Nature, of course,

is a lot of things. It is weather and climate, soils,

water, slope, aspect, and altitude. It is also a squirrel

that buries an acorn and a bird that eats a seed.

Nature is mushrooms, lichens, wildflowers, and

trees. To restore a truly natural system is beyond the

capacity and knowledge of humans. We can, however,

bring together the basic components and

characteristic plants and animals of an area (Table

5.1). Nature is assisted and directed by ecological

restoration. Natural processes will take over and

other components of the natural system will naturally

invade the restored system. Of course, some

systems are so devastated and the sources of plants

and animals available for reinvasion are so remote

that nearly everything must be provided by the

restorationist.

Don Falk (1990) of the Center for Plant Conservation

says in ecological restoration we seek not to

“preserve” a static entity but to protect and nurture

its capacity for change. “Restoration thus uses the

past not as a goal but as a reference point for the

future. If we seek to recreate the temperate forests,

tallgrass savannas, or desert communities of centuries

past, it is not to turn back the evolutionary clock

Habitat Characteristic Habitat Elements No. of

Species

1. Forest Cover 0–9 Years Old Forage, open areas, 49

high stem densities, dense cover

2. Old Growth–Forest Cover Large diameter, mast, snags, dens, 270

>100 Years Old logs, layered vegetation

3. Oak and Oak–Pine Forest Mast, cavity trees, and snags 80

>50 Years Old

4. Pole and Sawtimber with CrownForest cover with closed canopies 41

Closure over 80%

5. Sawtimber with 20–30% Sawtimber with moderate to open 61

Ground Cover understory

6. Oak forest >50 Years Old Sawtimber with moderate to dense 74

With a Dense Understory understory

7. Open and Semi-Open Forage, dense cover, some mast, 200

(nonforested) Habitats cavities

8. Permanent Water Sources Water for drinking, breeding, ——

feeding, roosting sites

9./10. Den Trees/Snags Cavities for nesting, roosting, song 155

and observation perches, feeding, shelter,

and eventually fallen woody material

Table 5.1. Representative habitat characteristics identified for the MarkTwainNational Forest (Putnam 1988).

but to set it ticking again.”

John Cairns (1988b) questions whether restoration

of ecological communities to their original

condition may be practical or possible. He offers

the following observations:

n Information about the original system may

be inadequate. For example, there is no

adequate description of the preindustrial Ohio

River that includes a detailed species inventory,

along with detailed descriptions of the

spatial relationships, trophic dynamics, and

functional attributes of the system.

n An adequate source of species for

recolonization may not be available because

of the uniqueness of the damaged community

or because the remaining communities

of this type would be damaged by removing

organisms for recolonization elsewhere.

n It may be impossible to put a halt to some of the

factors causing the damage. The notorious

example is acid rain, which may originate

many miles away in a political jurisdiction

over which the restorationist has no influence.

n The original ecosystem may have developed

as a result of a sequence of meteorological

events that are unlikely to be repeated and

may be difficult or impossible to reproduce.

n The sheer complexity of duplicating the

sequencing of species introductions is overwhelming.

To recreate the original community,

it is not only necessary that species

colonize at the appropriate time, but also that

some decolonize (disappear) at the appropriate

time.

The restoration efforts envisioned by this book

can be considered only partial restorations of natural

communities, designed to set the “evolutionary

clock ticking again.” A repertoire of target ecological

communities is compiled as Appendix A. They

represent over 200 different dominant communities

found in 30 natural regions of the continental

United States (see Chapter 6). These communities

can be targets for more restoration research as well

as starting points for initiating restoration efforts.

The species lists will, we hope, encourage nurseries

to propagate these plant materials for restoring

these basic ecological communities.

The type of restoration program undertaken

depends upon the goals for a site or landscape.

Goals can include aesthetics, reestablishment of

natural conditions, maintenance of a diversity of

plant and animal species, protection of the local

gene pool of particular species, reduction of grounds

maintenance costs and environmental impacts, and

creation of representative local ecosystems.

Often more than one goal is possible for any

given restoration project. While all the reasons

listed above are significant, goals may be quite

limited. For instance, restoration to increase the

carrying capacity for a given plant or animal is a

specific desired outcome. However, in the process

of restoring a specific habitat for a species, habitat

for other species will also result. A number of spinoff

benefits may result from any restoration project,

but the reported success or failure of the effort is

almost entirely based on a single criterion. A more

comprehensive, idealized goal would be to emulate

a healthy, ecologically robust, natural, self-regulating

system that is integrated with the ecological

landscape in which it is situated (Cairns 1991).

The focus of this handbook will be restoring

presettlement, predisturbance, and/or natural conditions.

Presettlement conditions are defined as

conditions encountered by the first European settlers

to describe the North American landscape.

Although early historical accounts of the first Europeans

are sketchy, we have a general idea of the

broad vegetation types present during the 1700s

and 1800s. Native Americans had inhabited North

America for centuries and through the pattern and

timing of harvests, as well as through the burning,

pruning, weeding, and planting of some sites, certain

mixtures and frequencies of plants and animals

were favored (for examples, see Boyd 1986;

Whitney 1994; Anderson 1993, 1996). Native

American land uses sustained native landscapes

rather than severely altering or degrading them.

The mutual existence of large herds of bison and

Native Americans contrasted with the rapid decline

in bison herds as European settlers moved

westward supports this idea. In fact, our understanding

of indigenous methods and practices may

lead to improved restoration methods and approaches

to restoration.

Predisturbance is the approximate condition of

the site prior to a major land degradation event.

Sometimes neither presettlement nor predisturbance

conditions are possible as a restoration goal. Information

regarding species composition and structure

may be lacking or the climate or another

important physical parameter may not exert the

same influence as it did in presettlement or

predisturbance times. The behavior of an ecological

system depends to some degree upon its unique

past, specific spatial setting, and current influences

(Pickett and Parker 1994). All ecosystems are the

product of climatological and biogeochemical sequences

that probably are unique (Cairns 1991).

This is why restoration projects must be very sitespecific

and flexible in terms of preferred goals.

Restoration to predisturbance condition may

not even be as appropriate as restoration to a

present natural condition. The difference between

predisturbance and natural conditions is that predisturbance

is a past condition, whether it is a few

years or a few decades. Predisturbance condition is

our best estimation of how an area appeared before

a human disturbance occurred. Natural condition

may be indistinguishable from predisturbance condition,

especially when one considers our lack of

detailed accounts of many ecological communities.

The difference in these conditions is that the

natural condition is based on a present day existing

model system (such as an adjacent intact natural

area) while predisturbance (as well as presettlement)

conditions are based on conceived previous or

historic accounts. Species in ecosystems are influenced

by both short- and long-term events, and the

inability to recreate a special sequence may mean

that attempts to restore to presettlement or

predisturbance conditions are unlikely to succeed

because of this fact alone (Cairns 1989). That is

exactly why restoration of natural conditions representative

of an existing local ecosystem (comparable

undisturbed system) is often more realistic.

As Dan Willard (quoted in Primack et al. [1995])

stated, “restore to a system that will work, not

necessarily the system that you wish would work.”

Some other types of restoration include rehabilitation

of selected attributes (e.g., forested) as well as

creation of an alternative ecosystem (Magnuson et

al. 1980).

Pickett and Parker (1994) stated that one of the

“pitfalls” of restoration ecology is “the assumption

that there is one reference state or system that can

inform restoration.” To assume that there is only

one ecologically legitimate or ideal system for a site

is a trap. However, Aronson et al. (1995) argue that

for the purposes of project design and evaluation, it

is desirable to establish at the outset some standard

of comparison and evaluation, even if it is arbitrary

and imperfect. Aronson et al. (1993a, 1993b) call

this the “ecosystem of reference.” This standard is

followed (in the broad sense) in the present handbook

by the use of Ecological Restoration Types

and Dominant Ecological Communities. A standard

of comparison and evaluation allows the

restorationist to track progress and to determine

success or evaluate the need to select another ecosystem

type for restoration on a particular site. The

creation of habitats in places they may never have

occupied is an approach with great potential for

sites that are so degraded that restoration to even a

semblance of the original habitat type is impractical.

This approach is valuable for landfilled sites,

surface mined areas, contaminated sites, or regionally

rare communities.

Matsui (1996) described an interesting project

from 20th-century Japan in which the goal was to

create a majestic, tranquil forest and landscape that

would be able to regenerate and survive almost

forever, not for economic reasons, but because this

was to be a holy place. Although the plan for the

project (Meji Shrine) was modeled to some extent

on natural forests of the area, no attempt was made

to create a natural ecosystem in the modern sense.

Instead, they assembled species from various areas

that they felt would grow well on the site. The

primary goal was for the forest to last forever with

little or no maintenance. While modeling a restoration

project after a natural community is typically

how restoration projects are planned, value (ecological

and cultural) also exists in creating habitats

for other purposes.

The best manner in which restoration projects

should be designed and evaluated is often not

clearly defined (Cairns 1989, Simberloff 1990,

Sprugel 1991). Many ecological and societal reasons

influence the choice of certain reference states,

including aesthetics, commodity production, ecosystem

services, and species protection, among

others (Pickett and Parker 1994). Aronson et al.

(1995) asked the question, “If no reference or

‘control’ is selected, how can the project be evaluated?”

For the purposes of this handbook, ecological

restoration means recreating both functional

and structural characteristics of a damaged ecosystem.

While this book concentrates mostly on vegetation,

discussions of other important considerations

also are presented.

A full-scale model need not exist; all else

failing, at least a few square feet or tens of square

feet may usually be found as a vestige of former

vegetation, and this can serve as a micro-model,

reference, and inspiration all at the same time

(Aronson et al. 1995). No criteria or guidelines that

provide ecological predictive capability are found

in the professional literature (Cairns 1989). Some

efforts will be so far from expectation that the

project should be terminated and a fresh start made

using a new design. Even an ecologically unsuccessful

project may appear successful to laymen

because a devegetated area has been revegetated or

because they may not understand the management

effort required to sustain the ecosystem (ibid.). All

restoration projects should have an explicit statement

of the product to be ultimately produced and

the condition at intermediate stages toward the

eventual goal. Each restoration project should have

several alternative standby plans so that if Plan A

fails, Plan B can be implemented. Communicating

that the outcome is uncertain is extremely important.

Incorporating an alternative course of action

into the restoration plan is equally important. In any

restoration project, the goals and the consequences

of meeting those goals must be part of the planning

process (Cairns 1991).

We now prefer to think in terms of many

equally possible ecosystem trajectories and of guiding

or piloting the ecosystem under study in one

direction or another (Aronson et al. 1995). Luken

(1990) used the phrase “directing ecological succession”

in order to manage for a particular successional

stage.

Ecological Restoration

Planning

Many steps are required to conduct a successful

restoration project. The most important component

for success is understanding that restoration takes

time. Actually, restoration, like other aspects of

looking after the earth, is an eternal vigil. As part of

that vigil, planting trees is an act of hope and

optimism. If one plants small trees and waits for a

canopy to plant understory shrubs, many years will

pass. Even a restored prairie of grasses and forbs

will take years before it resembles a natural community.

The level of maintenance required to look

after a forest while it is developing is, however,

relatively low compared to the meticulous, incessant

care of a golf green or a lawn. The long-term

maintenance of a restored natural ecosystem is

negligible.

The Natural Resources Management Staff of

the McHenryCounty (Illinois) Conservation District

(1996) have broken the process of natural

community restoration into three distinct phases:

structural, functional, and compositional. During

the structural phase a community's original structure

is recreated, as invasive brush, fencelines,

roadways, buildings, and other human modifications

to the site are removed. The functional phase

involves the reintroduction of ecological factors

such as fire, grazing, and hydrological processes

that shaped the site's ecological communities prior

to Euro-American settlement. Finally, in the compositional

phase, plant and animal species are

reintroduced and exotic species removed in order to

restore the community as closely as possible to its

historic composition. Planning a restoration project

in phases such as these improves the success rate.

Jackson et al. (1995) stated that while every