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Urban Agroforestry:

Connecting agroecology, permaculture, urban forestry and urban agriculture with agroforestry.

May 12, 2014

Steve Mann

Forest 8385

Ecological Principles of Agroforestry

University of Missouri, Columbia

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Table of Contents

Introduction……………………………………………………………….. 3

Urban Ecosystems and Ecosystems Services ……….. 4

Objective …………………………………………………………………… 6

Discussion …………………………………………………………………. 7

Agroecology …………………………………………………….. 7

Agroforestry …………………………………………………….. 8

Permaculture ………………………………………………….. 10

Urban Agriculture and Forestry …………………………. 11 Edible Urban Landscapes …………………………………. 12

Urban Food Forests………………………………………….. 12

Conclusions ………………………………………………………………. 14

References ……………………………………………………………… 16

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Introduction

There is strong evidence that humanity is having an unprecedented effect on the biosphere, and

these impacts are reducing human well-being in many places (Raudsepp-Hearne et al. 2010; MA

2005). Raudsepp-Hearne et al. (2010) see the potential of human action pushing ecosystems

beyond their limits causing irreversible ecological changes. Examples of these changes are global

warming induced melting of the polar ice caps, soil salinization, desertification, mass human

migrations and resource wars

The United Nations estimated in 2011 that more than half of the world population of over 7

billion people lived in urban areas (UN 2011). The percentage of urban residency in the United

States is even higher, 83 percent, 257 million people of an estimated total population of 310

million in 2011 (US Census Bureau 2014).

With this growing urban population there is a corresponding demand upon ecosystems resources

and services. Urbanization has become a major component of land-transformation, loss of

wetlands, and deforestation with resulting degradation of ecosystems services worldwide (Grimm

et al. 2000).

According to Rees and Wackernagel (1994), human ecological footprint is the area of productive

land needed to sustain a defined population indefinitely in their location. Using ecological

footprint analyses, it can be shown that a city requires a resource base

of non-urban land hundreds of times larger than its own area (Rees and Wackernagel 1996).

Because cities have such large ecological footprints and because much of humanity now lives in

urban areas, there is potential to apply agroecological, agroforestry and permaculture design

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practices to urban ecosystems for food production, biodiversity preservation, ecosystem

restoration and enhancement of ecosystem services (Raudsepp-Hearne et al. 2010).

Urban Ecosystems and Ecosystems Services

An urban ecosystem is a group of interacting species including humans and their local, non-biotic

environment functioning together as a unit. Rebele (1994) observed that the borders between

different ecosystems are often diffuse and overlapping. The urban environment can be defined as

one single ecosystem or composed of several individual ecosystem elements such as

neighborhoods, parks, watersheds and lakes.

Ecosystem services are the benefits derived from ecosystems. The Millennium Ecosystem

Assessment, MA (2005) divided ecosystem services into four broad categories:

• Provisioning resources, such as of food and water;

• Regulating, such as the control of water, climate and disease;

• Supporting, such as nutrient cycles and crop pollination;

• Cultural, such as spiritual, aesthetic and recreational benefits.

Since the 1990’s many authors have noted the effects of urbanization on the degradation of

biodiversity, hydrological systems, nutrient cycling, and energy flow in the urban ecosystem

(Bolund and Hunhammar 1999; Alberti 2005; Raudsepp-Hearne et al. 2010).

Some characteristics of urban ecosystem degradation are:

• Highly disturbed systems;

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• Rapid changes in soil and plant cover;

• Large swings in temperature and water availability;

• Largely impenetrable covering of the soil;

• Degraded soil life;

• Non native plantings, lawns and pioneer plants;

• Environmental stress on plants and animal.

There is a need to remediate these environmental issues and their effect on ecosystem health

and the well-being of urban dwellers (Alberti 2005).

Table 1. Urban ecosystems generating local and direct services relevant for Stockholm. Source: Bolund and Hunhammar (1999).

The amount and types of ecosystems services generated within the urban area (Table 1) can

contribute to the quality of urban life even though residents are still dependent on global

ecosystem services for their survival (Bolund and Hunhammar1999).

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Objective

In this paper I will review the literature of examples of the current theory and practice of

agroecology, agroforestry, and permaculture in urban ecosystems. I will look at possibilities for

integrating agroecology, agroforestry, and permaculture design principles in order to deal with

the unique challenges and opportunities of the urban ecosystem.

I suggest that urban ecosystems can become more sustainable using agroecological system

design, agroforestry, permaculture and edible landscaping practices and that understanding the

dramatic shift in human spatial and material relationships with the rest of nature is a key to

sustainability (Rees and Wackernagel 1996). These practices can lessen the ecological footprint

of urban areas by increasing the production of ecosystems services. Urban agriculture and

forestry can be integrated into an urban food forestry (UFF) design system utilizing

agroecological and permaculture principles and science (Clark and Nicholas 2013). By

distributing patches of perennial polyculture

Discussion

s at the neighborhood landscape level, ecosystem

services such as food provisioning, biodiversity, pollinators, water retention and filtering along

with nutrient cycling can be increased. Cultural ecosystems services such as food security,

recreational and employment opportunities and spiritual well-being can also benefit from a

resilient local food system. These integrated practices can become the foundations of Urban

Agroforestry.

First, I will explore the design systems and components that I suggest can be synthesized into

the practice of urban agroforestry. They are agroecology, agroforestry, permaculture, urban

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agriculture and forestry. I then look at some possibilities for using these practices in urban areas.

Agroecology

Agroecology is the holistic study of the environmental and human elements of agroecosystems.

It focuses upon the form, dynamics and functions of elements and the interrelationships and

processes in which they are involved (Altieri 2000). Agroecology is the application of ecological

concepts and principles to the design and management of sustainable agroecosystems

(Gliessman, 1998). Agroecology is also an environmental social movement supporting

sustainability and rural and urban development, using an ethical, science based approach (Wezel

et al. 2011).

Over the past two decades there has been a growing movement for a just and sustainable food

system in the United States. Local community initiatives address issues of food security, social

justice, urban agriculture, local food policy, community nutrition and local foodsheds. These local

sustainable food initiatives are using agroecological principles of systems based, participatory,

action-oriented, and a transdisciplinary focus for agri-food system change (Fernandez et al.

2013).

Agroforestry

Agroforestry is an intensive land-base management practice consisting of the integration of trees

and woody perennials with agricultural crops and/or livestock. This practice is intentionally

managed to optimize the beneficial interaction of the components on a biological, physical and

ecological level while providing for the economic needs of the farmer and his community (Lassoie

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et al. 2009). By the intentional use of the ecological wisdom of native ecosystems the practitioner

seeks to maximize the yields of multiple products in a sustainable manner (Gordon et al. 2009).

Agroforestry is an integrated land use management strategy that has the objectives of being

sustainable, stable and equitable (Lassoie et al. 2009). The inclusion of trees and woody

perennials adds greatly to the diversity of agroecosystems and can provide soil conservation

services, point source pollution mitigation, habitat and a wide array of agronomic products

including organic crops in a sustainable manner (Gold et al. 2009).

The inclusion of agroforestry practices in urban areas can consist of riparian and forest buffers,

windbreaks, multistrata home gardens and their temperate zone analog the food forest.

Urban Agroforestry practices at the landscape scale requires planning and integration of

agroforestry design into the green infrastructure of the larger urban landscape that includes a

matrix of urban, rural and forest lands (USDA 2011).

Riparian forest buffers are an agroforestry practice that can be of immense value in an urban

setting. These buffer systems adjacent to streams contain trees and shrubs along with warm

season native grasses and forbs. They act to filter sediment and landscape agrochemical runoff.

They can also provide added ecosystem service such as food production from tree crops, noise

screening, air pollution filtering and enhancement of biodiversity. McPherson et al. (1997)

estimated that tree cover in Chicago removed over 5500 t of air pollutants per year.

Many cities contain large amounts of degraded streams and watersheds that can benefit from

riparian forest buffers. Continuous riparian buffers along a watershed act as corridors for the

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movement of wildlife and arthropods (Schultz at al. 2009) and can be important areas of urban

ecosystems productivity and diversity.

Hedgerows, shelterbelts and windbreaks consisting of single or multiple rows of trees or woody

perennials planted around fields and structures for protection from winds. These diverse

vegetative structures not only protect fields from wind erosion but increase agroecosystem

species diversity and provide microclimates that benefit both crops and natural enemies of pests

(Andow 1991). In urban settings hedgerows can be used to create microclimate zones and

increase diversity by acting as ecological compensation areas (ECAs). ECAs are mosaics of non

crop vegetation in landscapes useful for enhancing biodiversity and conservation of species

(Burgio et al. 2004). Hedgerows act as refuges and corridors for the movement of species along

the urban/rural gradient and urban remnant patches (Gardiner 2014).

Permaculture

Permaculture is an alternative agroecology movement and ecological design system that was

defined in 1978 by Australians Bill Mollison and David Holmgrem. The original concept included

the idea of an evolving agricultural ecosystem modeled on nature using perennial plants in

polycultures that include animals (Mollison and Holmgrem 1978). Permaculture continues

toevolve and has gained widespread acceptance as a local environmental movement. Mollison

and Holmgrem were heavily influenced by the 1929 work of Russell Smith, Tree Crops: A

Permanent Agriculture and the work of American ecologist H.T. Odum (Holmgren 1992).

Permaculture is an integrative, ethics based sustainable design system highly suitable to urban

ecosystems.

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Polycultrures are multispecies cropping systems and may be considered a practical application of

ecological principles based on biodiversity, plant interactions and other natural regulation

mechanisms (Malézieux et al. 2009).

To date there has been little discussion in the scientific literature of permaculture despite its

grassroots acceptance and growth but this is beginning to change (Ferguson and Lovell 2013).

Urban Agriculture and Forestry

The growing of food crops in city gardens is an age old practice with increasing relevance for

today’s food security concerns. There is a rapid growth of urban agriculture utilizing formerly

vacant land of varying scales of production from single lot community gardens to urban farms of

many acres (Grewal and Grewal 2012). Production of food in urban neighborhoods can help

address growing concerns of hunger and obesity, which are exacerbated by the lack of access to

healthy food options. Policy makers at both the state and local level are addressing these

concerns and opportunities by adopting policies allowing production of crops, as well as allowing

the keeping of fowl and bees for production of honey and eggs (Grewal and Grewal 2012). The

state of Missouri and the city of Kansas City recently adopted laws that recognize urban

agriculture zones and provide among other things, property tax abatement in blighted areas and

wholesale water rates for urban growers (Ruess 2013).

Urban forestry can be defined as the management of forest resources in urban ecosystems for

the many benefits trees provides society (Konijnendijk et al. 2006; (Clark and Nicholas 2013).

Community forestry is the planting and care of trees by a community on common lands (Long

and Nair 1999). Urban forestry has many environmental and cultural benefits such as air and

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water filtering, fuel, noise reduction and when edible species are used, food production (Clark

and Nicholas 2013).

Edible Urban Landscapes

Zeunert (2012) has developed an edible landscape design practice, Aesthetic Foodscape Design

(AFD), that combines the productive yields of edible plants with the aesthetics of landscape

architecture’s spatial design practices. Zeunert, an Australian landscape architect, proposes that

we incorporate AFD in suitable, high visibility public locations in urban environments.

This idea has been embraces by a Kansas City, Missouri environmental action and education

group Food Not Lawns Kansas City who promote the growing of sweet potatoes in public space

as edible landscaping. Since 2008 the group has engaged in its Kansas City Sweet Potato Project

to educate the city residents and officials of both the environmental and nutritional benefits of

growing sweet potatoes in public spaces (figure 1).

Figure1) Sweet potato edible landscape planting at Central Patrol Division headquarters Kansas City Police Department. Kansas City, Missouri 2012. Source: the author.

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Urban Food Forests

The multistrata home garden is a traditional agroforestry land-use system consisting of

multipurpose trees and shrubs, herbaceous perennials and agronomic crops in polycultures

located in close proximity to individual homes (Fernandes and Nair 1986). Multistrata home

gardens typically consist of multiple species of plants occupying various spatial levels. By

integrating multiple levels of vegetative strata, designers seek to maximize the energy capture

and productivity of the system.

Table 2). Vegetative Strata of home gardens and food forests/forest gardens

De Clerck and Negreros-Castillo (2000) identified five horizontal and one vertical strata in mature

homegardens (Table 2) mimicking natural succession processes therefore providing the benefits

of multi level energy capture and resource utilization for increasing productivity over time.

Widespread in the tropics, the design of these productive polycultrure patches are being adopted

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by permaculture and urban agriculture practitioners in many temperate climate cities around the

world as templates for forest gardens or food forests.

The term Urban Food Forest (UFF) was coined by Swedish researchers, Clark and Nicholas in a

2013 paper to describe a set of practices based on home gardens, community orchards and

perennial urban agriculture. They found many examples of temperate Urban Food Forests in

many urban areas worldwide. Clark and Nicholas (2013) defined urban food forestry as ‘‘the

intentional and strategic use of woody perennial food producing species in urban edible

landscapes to improve the sustainability and resilience of urban communities.” Integrating

design principles and science from agroecology, agroforestry, orchard science, and plant

breeding into urban forestry resents a promising approach to improving urban landscape

productivity (Clark and Nicholas 2013).

A wide array of ecosystems services can be provides and enhanced by multistrata polycultrures

such as nutrient cycling, soil biotic diversity, food provisioning and water filtering and retention.

Conclusions

Adoption of agroecological, permaculture, urban forestry and urban agriculture design principles

and science to extend agroforestry practices in the context of the urban ecosystems can be a

valuable tool for building sustainable urban food systems and increase biodiversity and

ecosystems services.

The USDA Agroforestry Strategic Framework (ASF) suggests a focus on the integration of

agroforestry with food production in urban areas.

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ASF recognizes that over 80 percent of Americans now live in cities and that adoption of

agroforestry principles should start with urban populations and landscapes (USDA

2011).

I suggest that the integration of fruit, nut and nitrogen fixing trees and shrubs with vegetable

and native perennials and supporting species placed in a temporal and spatial matrix of

polyculture patches can be a major contributor to increasing urban sustainability and resilience.

Because of their complexity, the interaction between component species in UFF and polyculture

systems has been poorly researched. I suggest this is a valuable avenue of research for both

tropical and temperate climate urban agroforestry.

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