Animals in Agroecosystems - Agroecology: The Ecology of Sustainable Food Systems - page 276

Yet, as we saw in Chapter 1, the problems associated
with the disassociation of livestock and crops — and the
concomitant growth of large-scale confinement systems
for livestock and monoculture for crops — have come
back to haunt us (Nierenberg, 2005). Now that sustain-
ability is a primary goal of agriculture, and the costs of
the inputs that promoted specialization in the first place
are rising faster than the value of the crops they produce,
the idea of integrating crops and livestock has gained
prominence once again.

greatly, but its essence is to rotate a field between crops
grown for human consumption (often grains) and a forage
crop grazed by livestock. A variation on this theme is to
grow the forage crop without grazing and then harvest it
as feed for confined livestock animals. The grazed forage
rotation was once very common all over the world, with
the type of livestock, forage species, crop species, and
timing of the rotation all adapted to local conditions.
As has been discussed elsewhere in this text, crop
rotations in general have many benefits for overall agroeco-
system sustainability. Weed growth (Chapter 11), agro-
ecosystem diversity (Chapter 16), and water availability
(Chapter 9) are just a few factors that are positively
affected. When an animal component is included, both the
options for rotational sequences and the potential benefits
of the rotation are increased.

ANIMALS IN INTEGRATED
FARMING SYSTEMS

An “integrated farm” is one in which livestock are incor-
porated into farm operations “specifically to capture posi-
tive synergies among enterprises — to perform tasks and
supply services to other enterprises — not just as a market-
able commodity” (Clark, 2004). In this definition, “enter-
prise” refers to any focus or purpose of the farm system,
from saleable products to weed management to soil health.
The positive synergies that arise from integrating ani-
mals into agroecosystems come about in large part
because of the ecological complementarity of livestock
animals and crop and forage plants. Plants feed animals,
and animal excrement provides, in concentrated form, the
nutrients that plants require. Thus, an integrated system
— as opposed to one that is merely diversified — harnesses
this complementarity to move energy and nutrients
between the crop component and the animal component.
When animals are integrated into agroecosystems in this
way, more of the ecosystem processes operating in natural
systems can be incorporated into the functioning of the
agroecosystem, increasing its stability and sustainability.

Agropastoral Systems

In some mountainous areas of the world, particularly in
Pakistan, India, China, Nepal, and Bhutan, the most com-
mon traditional agricultural system is agropastoral in
nature. Crop production in warmer valleys is combined
with the grazing of livestock animals on highland pastures
during the summer. Usually the livestock provide the
major source of income and food. Despite the spatial
segregation in the summer, integration occurs in the use
of animal manure for fertilizer and the growing of forage
crops for winter animal feed.

Livestock in Agroforestry Systems

An agroforestry system, as discussed in Chapter 17, is a
system that integrates trees with crops, animals, or both.
When the focus is on the tree-animal combination, it is
referred to as a silvopastoral system, and when all three
(crops, animals, and trees) are integrated, the term agrosil-
vopastoral system is used.
The practice of silvopastoral agroforestry is best known
in the tropics, where trees can mitigate the impacts of heavy
rainfall, nutrient leaching, and intense solar gain. Some of
the most common silvopastoral agroecosystems involve the
use of trees as an overstory above natural or improved
pasture (Buck et al., 1999). Typically, forest is cleared and
specific trees are left to form the shade over the pasture,
and often some additional tree species of ecological or
economic value are planted as well, in patterns that ensure
good tree development. The management of the animals in
livestock agroforestry systems is the key, because it must
meet the needs of the trees — and the crops, if they are
present — and the animals at the same time.
Both trees (Chapter 17) and livestock animals can
have many positive impacts on an agroecosystem; so when
the two are combined many components of sustainability
can be brought together. The journal Agroforestry Systems

E XAMPLES OF I NTEGRATED S YSTEMS

The basic concept of integrating the raising of animals and
the growing of crops in the same agroecosystem finds a
variety of expressions around the world. The livestock com-
ponent can include cattle, sheep, goats, pigs, rabbits, horses,
oxen, yaks, water buffalo, poultry, waterfowl, fish, shellfish,
bees, silkworms, or a variety of other species that can provide
food, work, manure, ecosystem services, or some combina-
tion of these. The crop component can include grains, pulses,
oil seeds, grazed forages, vegetables, potatoes, fruit or nut
trees, fruit vines, and other food crops. Given these options,
the possibilities for integration are nearly endless. Four of
the most important types of systems are described below.

Crop Rotations with a Grazed Forage Phase

The most widespread and widely adaptable method of
integrating livestock animals into cropping systems is the
grazed forage rotation. The specifics of the practice vary