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Agroecological Principles for the Conversion of Farming Systems: Principles, Applications, and Making the Transition

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Agroecology: Principles for the Conversion and Redesign of Farming
Systems
Nicholls CI1, Altieri MA2* and Vazquez L3
1Department of International and Area Studies, University of California, Berkeley, USA, Latin American Scientific Society of Agroecology (SOCLA)-Colombia
2Department of Environmental Science, Policy and Management, University of California, Berkeley, USA, Latin American Scientific Society of Agroecology (SOCLA)-
Chile
3Latin American Scientific Society of Agroecology (SOCLA)-Cuba
*Corresponding author: Altieri MA, Department of Environmental Science, Policy and Management, University of California, Berkeley, USA, Latin American Scientific
Society of Agroecology (SOCLA)-Chile, Tel: 510-642-9802; E-mail: agroeco3@berkeley.edu
Received: February 22, 2016; Accepted: March 30, 2016; Published: April 05, 2016
Copyright: © 2016 Nicholls CI, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author and source are credited.
Abstract
Modern agroecosystems require systemic change, but new redesigned farming systems will not emerge from
simply implementing a set of practices (rotations, composting, cover cropping, etc.) but rather from the application of
already well defined agroecological principles. These principles can be applied using various practices and
strategies, each having different effects on productivity, stability and resiliency of the target farming system. By
breaking the monoculture nature of farming systems, agroecological diversification aims at mimicking ecological
processes leading to optimal nutrient cycling and organic matter turnover, soil biological activation, closed energy
flows, water and soil conservation and balanced pest-natural enemy populations. All these processes are key for
maintaining the agroecosystem’s health, productivity and its self-sustaining capacity. By enhancing functional
biodiversity, a major goal of the conversion process is achieved: strengthening the weak ecological functions in the
agroecosystem, allowing farmers to gradually eliminate inputs altogether by relying instead on ecological processes
and interactions.
Keywords Agroecology; Conversion; Diversied farming systems;
Sustainability; Resilience
Introduction
Modern agriculture has consisted in the replacement of natural
plant communities with articially supported crop communities.
Human manipulation and alteration of ecosystems for the purpose of
establishing agricultural production has turned modern
agroecosystems into highly simplied systems, to the point that they
are structurally and functionally very dierent from natural
ecosystems. e self-regulation capacities of natural plant communities
are lost when farmers modify them by promoting monocultures. e
more intensely such communities are simplied, the more frequent
and serious the ecological unbalances of simplied cropping systems
[1].
Reliance on homogeneous monoculture production systems is no
longer socially, economically and ecologically desirable as these
systems compromise biodiversity, utilize resources ineciently, are
highly energy dependent, impose a major ecological footprint, are
susceptible to pest outbreaks and are also vulnerable to climatic
variability [2]. A recent analysis concluded that major grain crops are
genetically uniform and thus extremely vulnerable to disease
epidemics and climatic events [3]. is uniformity is linked to
economic and legislative forces that favour monocultures and
simplication [3]. In fact, increased demand for corn grain as a biofuel
is altering diversity at the landscape level and consequently the
ecosystem services they provide. For example, Landis et al. [4]
concluded that recent biofuel-driven growth in corn monocultures in
four US Midwest states resulted in lower landscape diversity, which in
turn decreased habitat of natural enemies of soybean pests, thus
reducing bio control services by 24%. Reduced biological control cost
soybean farmers about $58 million per year due to reduced yield and
increased pesticide use [4]. Similarly, Chinese researchers found in a
two-year study of seventeen 1500 m-radius sites in China, that input of
nitrogen fertilizer and cropland expansion compromised the ability of
natural enemies to control cereal aphids leading to a disturbance of
interspecic relationships thus enhancing reliance on pesticides [5].
Other than deploying new crop varieties and applying more than
5.2 billion pounds of pesticides worldwide, ecologically speaking, little
has been done to reduce the pest susceptibility of industrial
agroecosystems or to enhance their adaptability to changing climatic
patterns [6]. Many agroecologists have suggested that agroecological
strategies that break the nature of monocultures and favour eld
diversity as well as landscape heterogeneity are the most viable path to
increase productivity, sustainability and resilience of agroecosystems
[7,8]. is recommendation is based on observations and experimental
evidence that assert the following trends: (a) when agroecosystems are
simplied, key functional species are eliminated shiing the balance of
the system from a desired to a less desired functional state, aecting
the agroecosystem’s capacity to respond to changes and provide
ecosystem services and (b) the higher the vegetational diversity of
agroecosystems, the greater the capacity of the agroecosystem to buer
against pest and disease problems as well as to shiing climatic
patterns [9].
Research has shown that diversied agroecosystems can reverse
yield reduction trends when a variety of crops and varieties are
deployed in various temporal and spatial schemes as each responds
dierently to external shocks. In a recent review, researchers found that
Journal of Ecosystem & Ecography Nicholls et al., J Ecosys Ecograph 2016, S5:1
http://dx.doi.org/10.4172/2157-7625.S5-010
Research Article Open Access
J Ecosys Ecograph Global Climate Change ISSN:2157-7625 JEE, an open access journal
when compared to conventional monocultures, diversied
agroecosystems supported greater biodiversity, better soil quality and
water-holding capacity, and exhibited greater energy output/input
ratios, and resilience to climate change. Diversied farming systems
also enhance the regulation of weeds, diseases, and insect pests while
increasing pollination services [10].
As farmers initiate the agroecological conversion of their farming
systems, several benecial changes in soil properties, microclimatic
conditions, plant diversity and associated benecial biota occur, slowly
creating the foundations for enhanced plant health, crop productivity
and resiliency [11]. Agroecosystems undergoing ecological conversion
operate as complex systems with emergent properties, and therefore
management decisions should take into consideration the special
behaviors and properties of complex systems [12]. It is clear however
that it is not diversity per se that enhances stability in agroecosystems
but rather ‘functional biodiversity’, a set of biota clusters that play key
roles in the determination of agroecosystem processes and in the
provision of ecological services (soil fertility, pest regulation, etc.)
thereby reducing the need for external farm inputs [7,13].
In this paper, we argue that modern agroecosystems require
systemic change, but new redesigned farming systems will not emerge
from simply implementing a set of practices (rotations, composting,
cover cropping, etc.), but rather from the application of already well
dened agroecological principles [7,13]. ese principles can be
applied by way of various practices and strategies, and each will have
dierent eects on productivity, stability and resiliency within the farm
system. Agroecological management leads to optimal nutrient cycling
and organic matter turnover, soil biological activation, closed energy
ows, water and soil conservation and balanced pest-natural enemy
populations. All these processes are key for maintaining
agroecosystems health, productivity and its self-sustaining capacity
[14]. e challenge to align agricultural systems with ecological
principles is immense, especially in the current context of agricultural
development where specialization, short-term productivity and
economic eciency are emphasized.
e conversion of farming systems
e reversion of agroecosystems that have already undergone major
ecological simplication implies a process of conversion from a high-
input monoculture management system to a diversied system with
very low external inputs [15]. Most farmers start the conversion
process slowly, taking time to gain experience with a more diverse
cropping system, experimenting on a small scale and thus reducing
risk and to learn to be exible enough to adapt to changing conditions.
Stages in the transition: e conversion to organic management
aects the whole farming system, not only single enterprises. Crop
rotations are the main management practices that overwhelmingly
organic farmers utilize during conversion as these inuence forage
production, fertility building and are an integral part of weed, pest, and
disease management strategies. A major emphasis during conversion is
improving overall soil quality by incorporating organic matter into the
soil via the application of animal manures or compost, as well as
skillful cover cropping and well planned rotations. In most organic
systems cover crops are the source of the vast bulk of organic carbon
inputs needed for the desired soil microbial community and adequate
nutrient pool [11]. Unfortunately pushed by market forces that
privilege specialization, many organic farmers tend to replace practices
such as rotations, cover cropping, etc. with a set of organic technology
packages and input substitutions, making their operations dependent
and intensive.
Many authors have conceptualized agroecosystem conversion as a
transitional process with three marked phases [16]:
1. Increased eciency of input use through integrated pest
management or integrated soil fertility management.
2. Input substitution using environmentally benign inputs
(botanical or microbial pesticides, bio fertilizers, etc.).
3. System redesign or diversication through optimal crop/animal
assemblages which encourage interactions that allows the
agroecosystem to sponsor its own soil fertility, natural pest
control, and crop productivity.
Many of the practices that are currently being promoted as
components of sustainable agriculture fall in categories 1 and 2. Both
of these stages decrease agrochemical input use and oer benets in
terms of lower environmental impacts as well as economic advantages
by reducing production costs. Incremental changes tend to be more
acceptable to farmers as drastic modications may be viewed as highly
risky. But does the adoption of practices that increase the eciency of
input use or that substitute biologically based inputs for pesticides and
fertilizers, while leaving the monocultural structure intact, have the
potential to lead to the productive redesign of agroecosystems? A true
agroecological conversion calls into question monoculture and the
dependency on external inputs [15].
In general, the ne-tuning of input use through approaches such as
Integrated Pest Management (IPM) or Integrated Soil Fertility
Management (ISFM) does little to transition farmers toward an
alternative system independent from external inputs. In most cases
IPM translates to “intelligent pesticide management” emphasizing the
selective use of pesticides according to a pre-established economic
threshold, which pests oen surpass in monoculture situations. Input
substitution used by the large majority of organic farmers follows the
same paradigm of conventional farming by trying to overcome the
limiting factor with biological or organic inputs. Many of these
“alternative inputs” have become commodied, therefore farmers are
still dependent on input suppliers [17]. In California, many organic
farmers cultivating grapes and strawberries apply between 12-18
dierent types of biological inputs per season. In addition to
enhancing production costs, many products used for one purpose
aect other aspects of the system. For example, Sulphur which is
widely used to control foliar diseases of grapes, can also wipe out
populations of Anagrus parasitic wasps, key regulators of leaopper
pests. us farmers become trapped in an “organic treadmill”.
Gliessman [18] argues that improvements in eciency of input use
and input substitution are not enough to address the challenges facing
modern agriculture. Instead, he argues that farming systems must be
redesigned based on a new set of ecological relationships. is entails
approaching conversion as an ecological transition of agriculture based
on notions of agro-ecology and sustainability. System redesign arises
from the application of agroecological principles that lead to the
transformation of the structure and function of agroecosystems by
promoting management guided to ensure the following processes [19]:
1. Increasing above and below ground biodiversity.
2. Increasing biomass production and soil organic matter content.
3. Ecient use of soil nutrients, water, solar energy, seeds, soil
organisms, pollinators and natural enemies.
4. Optimal planning of plant-animal sequences and combinations.
Citation: Nicholls CI, Altieri MA, Vazquez L (2016) Agroecology: Principles for the Conversion and Redesign of Farming Systems. J Ecosys
Ecograph S5: 010. doi:10.4172/2157-7625.S5-010
Page 2 of 8
J Ecosys Ecograph Global Climate Change ISSN:2157-7625 JEE, an open access journal
5. Enhancement of functional complementarities and interactions
between soil, crop and biotic components.
Ultimately system redesign consists in the establishment of an
ecological infrastructure that through plot to landscape-scale
diversication, encourage ecological interactions that generate soil
fertility, nutrient cycling and retention, water storage, pest/disease
regulation, pollination, and other essential ecosystem services [20].
e associated cost (labor, resources, money) to establish the ecological
infrastructure of the farm (living fences, rotation, insect habitats, etc.)
during the redesign phase tends to be high in the rst 3-5 years. Once
the rotation and other vegetational designs (cover crops, polycultures,
eld borders, etc.) start lending ecological services to the farm, key
ecological processes (nutrient cycling, pest regulation, etc.) are set in
motion, the need for external inputs is reduced and thus maintenance
costs start decreasing as the functional biodiversity of the farm
sponsors ecological functions (Figure 1).
Figure 1: Maintenance costs during the transition towards system
redesign.
Agroecology promotes principles rather than rules or recipes to
develop an agroecological production system out of a conventional
farm in a stepwise transition process. Farmers are increasingly
challenged to make use of their intellectual and communication skills
throughout this period of transition because they have to optimize
conventional input-use eciency, substitute synthetic with organic
inputs, and re-design the production system. Such a transition is
knowledge intensive and requires self-study, and ideally a reluctance to
take major risks, demanding 3–5 years for the creation of an
agroecosystem. Agroecology as a farming approach can be more labor-
intensive, but benets such as the development of capabilities, the
services to neighboring ecosystems, and the provision of healthy food
mostly justify the extra eort the farmer puts in redesigning her/his
farming system [21].
Changes in soil biology and crop productivity
Aer 3-4 years of conversion, changes on soil properties become
apparent. In general, organically managed soils exhibit higher
biological activity than soils managed conventionally. In a long term
and well controlled study conducted in Switzerland researchers found
root length of crops colonized by mycorrhizae in organic farming
systems was 40% higher than in conventional monocultures [22]. Crop
plants colonized by VAM usually exhibit signicantly higher biomass
and yields compared to nonmycorrhizal (NM) plants, under water
stress conditions, as VAM colonization increases water use eciency
[23]. Biomass and abundance of earthworms were higher by a factor of
1.3 to 3.2 in the organic plots as compared with conventional ones [2].
Activity and density of predators such as carabids, staphylinids, and
spiders in the organic plots was almost twice that of the conventional
plots [22].
Percent nitrogen, phosphorus and potassium, pH, organic matter
and some micronutrients increase with time, reaching values many
times signicantly higher than at the start of the conversion [24]. Many
studies have revealed better performance of organic agriculture than
conventional systems on various sustainability metrics, including
species richness and abundance, soil fertility, nitrogen uptake by crops,
water inltration and holding capacity, and energy use and eciency
[10].
In terms to productivity, the Switzerland study showed that mean
organic crop yield was only 20% lower over a period of 21 years
indicating an ecient production. In the organic systems, the energy
to produce a unit of crop dry matter was 20 to 56% lower than in
conventional and also 36 to 53% lower per hectare [22]. Yields usually
decline during the rst 3-5 years of conversion, but as a recent
metanalysis suggests, organic yields are only 19.2% lower than
conventional yields, a smaller yield gap than previously estimated [25].
ese researchers found that diversication schemes such as crop
rotations and multiple cropping, reduced the yield gap when the
methods were used by organic farmers.
Once agroecosystems reach the last stage of the conversion process
(system redesign), and polycultural cropping systems are prevalent,
total production output increases at the farm level. e mechanisms
that explain higher productivity in polycultues are embedded in the
process of facilitation. Facilitation occurs when one crop modies the
environment in a way that benets a second crop, for example, by
lowering the population of a critical insect pest, or by releasing
nutrients that can be taken up by the second crop [26]. us
mechanisms are related to the lower pest and pathogen incidence
generally found in intercrops and to the higher resource use eciency
of crops with dierent root systems and leaf morphology. Resource
capture and resource conversion eciency and other concepts have
also been suggested as mechanisms underlying polyculture yield
advantages. A school of thought concerning the resource use of
intercropping systems states that a combination of two contrasting
species, usually legumes/cereals, would lead to greater overall
biological productivity than each species grown separately because the
mixture can use resources more eectively than under separate
monocultures [27]. Huang et al. [28] explored how corn-faba bean,
corn-soybean, corn-chickpea, and corn-turnip intercropping aected
yields and nutrient acquisition in Chinese agricultural elds. e
authors found that the intercropping systems more eciently removed
nitrogen from the soil – indicating increased resource use eciency in
the polycultures. Zhang and Li [29] propose a “competition-recovery
production principle based on several years of studies on
intercropping of short-season/long-season species. ey suggest that
interspecic interaction increases growth, nutrient uptake and yield of
dominant species, but decreases growth and nutrient uptake of the
subordinate species during the co-existence stage of two crop species.
Aer the dominant species is harvested, the subordinate species has a
recovery or complementary process so that the nal yields remain
unchanged or even increase compared with corresponding sole
species.
Citation: Nicholls CI, Altieri MA, Vazquez L (2016) Agroecology: Principles for the Conversion and Redesign of Farming Systems. J Ecosys
Ecograph S5: 010. doi:10.4172/2157-7625.S5-010
Page 3 of 8
J Ecosys Ecograph Global Climate Change ISSN:2157-7625 JEE, an open access journal
Agroecological principles for the conversion
As an applied science, Agroecology uses well established ecological
principles for the design and management of diversied
agroecosystems where external inputs are replaced by natural processes
such as natural soil fertility, allelopathy and biological control (Table
1). Agroecology does not promote technical recipes but rather the
above principles, which when applied in a particular region take
dierent technological forms depending on the prevailing socio-
economic and biophysical circumstances of farmers [7,13]. Each
practice is linked to one or more principle thus contributing to its
manifestation in the function of the agroecosystems (Table 2). e
applied practices set in motion ecological interactions that drive key
processes for agroecosystem function (nutrient cycling, pest
regulation, productivity, etc.) (Figure 2).
Figure 2: Agroecological principles for the conversion of farming
systems.
Enhance the recycling of biomass, with a view to optimizing organic matter
decomposition and nutrient cycling over time
Strengthen the “immune system” of agricultural systems through enhancement
of functional biodiversity – natural enemies, antagonists, etc., by creating
appropriate habitats
Provide the most favorable soil conditions for plant growth, particularly by
managing organic matter and by enhancing soil biological activity
Minimize losses of energy, water, nutrients and genetic resources by enhancing
conservation and regeneration of soil and water resources and agrobiodiversity
Diversify species and genetic resources in the agroecosystem over time and
space at the field and landscape level
Enhance beneficial biological interactions and synergies among the components
of agrobiodiversity, thereby promoting key ecological processes and services
Table 1: Agroecological principles for the design of biodiverse, energy
ecient, resource-conserving and resilient farming systems [7,13].
Agroecology does not promote a few magic bullet solutions
divorced from local contexts and disseminated following top down
approaches. Rather, it relies on a set of complex interactions that
emerge when adequate combinations of various practices are
operationalized on each farm [30]. e array of cultural practices used
by each farmer result in functional dierences that cannot be
accounted for by any single practice. is is what Andow and Hidaka
[31] called “a production syndrome” dened as a set of management
practices that are mutually adaptive and when acting together lead to
high performance. However, subsets of this collection of practices may
be substantially less adaptive; that is, the interaction among practices
leads to improved system performance not explained by the additive
eects of individual practices. One of the frustrations of research in the
organic/conventional yield gap has been the inability of low-input
practices to outperform conventional practices in side-by-side
experimental comparisons, despite the success of many organic and
low-input production systems in practice. A consistent yield gap of
19-25% is reported when comparing organic and conventional
agricultural systems, but interestingly the yield gap is reduced
substantially when organic farmers adopt multi-cropping and complex
crop rotations, evincing the “production syndrome” [25].
Management practice Principle to which they contribute*
1 2 3 4 5 6
Compost application x x
Cover crops and/or green
manures
x x x x x x
Mulching x x x
Crop rotation x x x x
Use microbial/botanical
pesticides
x
Use of insectary flowers x x x
Living fences x x x x
Intercropping x x x x x x
Agroforestry x x x x x x
Animal Integration x x x x x
*Each number refers to an agroecological principle listed in Table 1
Table 2: Relative contribution of several management practices to one
or more agroecological principles [32].
Depending on how it is concretely applied and complemented or
not by other practices, one particular practice can sometimes act as an
“ecological turntable” by activating various processes (nutrient cycling,
biological control, antagonism, allelopathy, etc.), all essential for the
health and productivity of a farming system. Cover crops for example
can exhibit several multiple eects simultaneously including
suppression of weeds, soil borne diseases and pests, protect the soil
from rain and runo, improve soil aggregate stability, add active
organic matter, x nitrogen and scavenge for nutrients [7]. Clearly,
each production system represents a distinct group of management
practices and by implication, ecological relations. is re-emphasizes
the fact that agroecological designs are site-specic and what may be
applicable elsewhere are not the techniques but rather the ecological
principles that underlie sustainability. It is of no use to transfer
technologies from one site to another, if the set of ecological
interactions associated with such techniques cannot be replicated.
Agroecological interactions in redesigned farming systems
System redesign is the last stage in the agroecological conversion
process and consists in practical steps to break the monocultural
Citation: Nicholls CI, Altieri MA, Vazquez L (2016) Agroecology: Principles for the Conversion and Redesign of Farming Systems. J Ecosys
Ecograph S5: 010. doi:10.4172/2157-7625.S5-010
Page 4 of 8
J Ecosys Ecograph Global Climate Change ISSN:2157-7625 JEE, an open access journal
structure by restoring agricultural biodiversity at the eld and
landscape level. Biodiversity enhancement is the cornerstone strategy
of system redesign, as increasing diversity within functional groups
promotes key processes (pest regulation, nutrient cycling, etc.)
fundamental for agroecosystem function [33]. Higher plant diversity
within the cropping system determines higher diversity of above and
below ground associated biota which in turn leads to more eective
pest control and pollination and to tighter nutrient cycling [19].
Pest Regulation
Over the last 40 years, many studies have evaluated the eects of
crop diversity on the abundance of insect pests. An early review by
Risch et al. [34] summarized 150 published studies exploring the
eects of diversifying an agroecosystem on insect pest densities. 198
total herbivore species were examined in these studies. Fiy-three
percent of these species exhibited lower densities in the more
diversied systems. Eight years later, Andow [35] analyzed results from
209 studies involving 287 pest species, and found that compared with
monocultures, the population of pest insects was lower in 52% of the
studies, and higher in 15% of the studies. Of the 149 pest species
exhibiting lower densities in intercropping systems, 60% were
monophagous and 28% polyphagous species [31].
e abundance of predators and parasitoids of pests was higher in
intercrops in 53% of the studies and lower in 9%. Tonhasca and Byrne
[36] analyzing 21 studies comparing pest suppression in polyculture
versus monoculture, found that polycultures signicantly reduced pest
densities by 64%. In a later meta-analysis involving 148 comparisons
Letourneau et al. [37] found that farms with species-rich vegetational
schemes exhibited a 44% increase in abundance of natural enemies, a
54% increase in pest mortality, and consequently a 23% reduction in
crop damage when compared to monoculture farms. Unequivocally,
earlier reviews and recent meta-analyses suggest that crop
diversication strategies lead to natural enemy enhancement,
reduction of insect pest densities, and reduced crop damage, from a
combination of ecological mechanisms.
Plant pathologists have also observed that mixed crop systems can
decrease pathogen incidence by slowing down the rate of disease
development and by modifying environmental conditions so that they
are less favorable to the spread of certain pathogens [38]. For soil
borne or splash borne diseases, Hiddink et al. [39] found that
intercropping patterns and variety mixtures signicantly reduced
disease in comparison to monocultures. Host dilution was frequently
proposed as the mechanism for reducing the incidence of pathogens.
Other mechanisms, such as allelopathy and microbial antagonists, can
also act to reduce disease severity in diversied farming systems [40].
Lower disease incidence contributes to less crop damage and higher
yields in mixed crops as compared to corresponding monocultures.
Weed ecologists posit that many intercrops are oen superior to
monocultures in weed suppression, as crop combinations exploit
resources more eciently than sole crops, thus suppressing the growth
of weeds more eectively through greater preemptive use of resources
[41]. Alternatively, intercrops may still over yield sole crops without
necessarily suppressing weeds. e latter situation arises if the yields of
intercropping result from (1) better use of resources for which crops
and weeds did not compete, or (2) other mechanisms such as increased
eciency of resource conversion, shis in the partitioning of crop
biomass, modications of microhabitats, and decreased insect or
disease pressures, none of which would necessarily result in the
removal of nutrients, water or light from weeds [42].
Yield stability in the midst of climatic variability
Intercropping is popular among small farmers in the developing
world because they perceive this practice as more stable than
monocropping, enabling them to produce various crops
simultaneously while minimizing risks [43]. Data from several
experiments on mixed cropping sorghum/pigeon pea showed that for a
given ‘disaster’ (drought, frost, etc.), pigeon pea monoculture would
fail one year in ve, sorghum monoculture would fail one year in eight,
but intercropping would fail only one year in thirty-six [44]. Many
researchers have reported that polycultures exhibit more stable yields
and less productivity declines during a drought than monocultures.
For example, Natarajan and Willey [45] subjected polycultures of
sorghum and peanut, millet and peanut, and sorghum and millet to
water stress. ey found that all the polycultures over yielded
consistently at moisture availability levels ranging from 297 to 584 mm
of water applied over the growing season. e rate of over yielding
increased with water stress so that productivity dierences between
monocultures and polycultures became more accentuated as water
stress increased [45]. One possible mechanism explaining the above
observations is that polycultures tend to have higher levels of soil
organic matter content [46] which in turn enhances the soil’s moisture
holding capacity, leading to higher available water for plants, which
positively inuences resistance of crop plants to drought conditions
[47,48]. Hudson [49] showed that as soil organic matter content
increased from 0.5 to 3%, soil water available to plants doubled. Several
trials have shown that diversied farming systems exhibit greater water
holding capacity than conventional farming systems. In northeastern
US, ve drought years occurred between 1984 and 1998 and in four of
them organic maize out yielded conventional maize by signicant
margins. Organic maize yielded between 38% and 137% relative to
conventional maize. e primary mechanism of the higher yield of the
organic maize systems was the higher water-holding capacity of the
soils in those treatments. Soils in the organic plots captured more
water and retained more of it in the crop root zone than in the
conventional systems [11].
In a 37-year trial, Reganold [50] found signicantly higher soil
organic matter levels and surface soil moisture content in soils
managed organically than in soils managed conventionally. Many
intercropping systems also improve the water use eciency compared
to monoculture. In China, water use eciency in a potato-bean
intercropping system was 13.5% greater than in monoculture (10.15
kg/m3) [30]. Morris and Garritty [51] found that water-utilization
eciency by intercrops greatly exceeds that of crops grown in
monocultures. ey do so by promoting the full use of soil water by
plant roots, increase the water storage in root zone, reduce the inter-
row evaporation, but also by controlling excessive transpiration, and by
creating a special microclimate advantageous to plant growth and
development.
In hillside situations prone to tropical storms, intercrops can
signicantly provide soil erosion protection as their complex canopies
aord a better soil cover. Under heavy rains more complex canopies
and plant residues that cover the soil reduce the impact of raindrops
whose impact can detach soil particles and promote erosion [52].
Surface runo is slowed by the soil cover, allowing improved moisture
inltration. Not only does living and dead cover provide soil
protection, but also the extensive root system of polycultures stabilize
Citation: Nicholls CI, Altieri MA, Vazquez L (2016) Agroecology: Principles for the Conversion and Redesign of Farming Systems. J Ecosys
Ecograph S5: 010. doi:10.4172/2157-7625.S5-010
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J Ecosys Ecograph Global Climate Change ISSN:2157-7625 JEE, an open access journal
the soil by creating a complex mat in the prole thus holding the soil
[50]. In Elora, Ontario [53] soil loss was signicantly lower in a silage
corn intercropped with red clover system than in the corn
monoculture. Runo reduction with the corn/clover system ranged
from 45 to 87% and between 46-78% reduction of soil loss was
achieved with the corn/clover system.
Linkages between soil fertility and insect pest incidence
Although crop diversication strategies in the form of multi-species
rotations, cover crops, agroforestry, and intercrops are key in the
conversion process, when complemented by frequent applications of
organic materials (crop residues, animal manures, and composts)
surprising eects on plant health, soil quality and productivity can be
noticed. ese hidden connections have been totally missed by
entomologists and other agricultural researchers who have explained
pest outbreaks in agroecosystems solely as a consequence of the
absence of natural enemies or development of pesticide resistance by
insect pests or secondary pest outbreaks due to disruptions promoted
by insecticides [54]. Western scientists have been largely unaware of
the theory of trophobiosis oered by French scientist Francis
Chaboussou [55] who as early as 1967 contended that pest problems
were linked to nutritional unbalances of crop plants and destruction of
soil biological activity. He explained that heavy applications of nitrogen
(N) fertilizers, which are highly soluble, increase the cellular amounts
of N, ammonia and amino acids, at a rate faster than plants can
synthesize them into proteins. Reduction of protein synthesis leads to
temporary accumulation of free N, sugars and soluble amino acids in
the foliage, all substances needed for reproduction by certain insect
pests and plant pathogens. Chaboussou’s postulated that insect pests
and diseases grow and multiply faster when plants contain more
soluble free nutrients caused by the inhibition of protein synthesis. He
also believed that a soil with a balanced microbial life was key for the
uptake of micronutrients by the plants. is is important because a
deciency of micronutrients can also cause protein synthesis reduction
which in turn leads to build-up in nutrients needed by pests and
pathogens [55].
In the last 20 years a number of research studies have emerged
corroborating Chaboussou’s assertions, showing that the ability of a
crop plant to tolerate insect pest and disease incidence is tied to
optimal soil quality properties. Soils with high organic matter content
and rich biological activity exhibit good soil fertility as well as complex
food webs with many benecial microorganisms that prevent infection
[56]. In a series of controlled greenhouse experiments, when given a
choice of maize grown on organic versus chemically fertilized soils
collected from nearby farms, European corn borer (
Ostrinia nubilalis
)
females signicantly laid more eggs in the plants grown on chemically
fertilized soils [57].
Although there was signicant variation in egg laying among plants
grown on conventionally managed soil, in plants grown in organic
managed soil egg laying was uniformly low. Pooling results across all
sampled farms showed that variation in egg laying was 18 times higher
among plants grown in conventionally managed soil than among
plants grown on organic soils [57]. In similar studies conducted in
China by Hsu et al. [58] indicated that
Pieris rapae crucivora
butteries preferred to lay eggs on foliage of chemically fertilized
cabbage plants and the larvae grew faster on plants fertilized with
synthetic fertilizer. e results of this study suggested that a proper
organic treatment can increase plant's biomass production and exhibit
a lower pest occurrence. is dampening of plant susceptibility to
insects and disease led Phelan et al. [57] to propose the concept of
biological buering, which asserts that a more complex soil
community supported by the inux of active organic matter tends to
moderate uctuation in the soil environment and promote greater
ecological stability. During the conversion process additional
mechanisms that transfer this stability above ground through greater
plant resistance may include (a) modulation of plant mineral nutrient
availability by the soil food web, and/or (b) an enhanced plant systemic
defense induced by benecial microbes interacting with plant roots
[59].
Conclusions
A key agroecological principle applied since the initiation of the
conversion process, is the diversication of the agroecosystem by
adding regenerative components such as combining plants in
intercropping arrangements, crops and trees in agroforestry systems,
animals and trees in silvopastoral systems, using legumes as cover
crops or in rotations, etc. A community of organisms in an
agroecosystem becomes more complex when a larger number of
dierent kinds of plants are included, leading to more interactions
among associated arthropods and microorganisms which are part of
above and below ground food webs. As diversity increases, so do
opportunities for coexistence and benecial interactions between
species benetting agroecosystem sustainability [60]. Diverse systems
encourage complex food webs, which entail more potential
connections among plants, insects and microbes, creating alternative
paths for energy and material ow. For this reason, a more complex
community exhibits less uctuation in the numbers of undesirable
organisms and a more stable production [61]. By enhancing functional
biodiversity, a major goal of the conversion process is achieved:
strengthening the weak ecological functions in the agro-ecosystem,
allowing farmers to gradually eliminate inputs altogether by relying
instead on ecosystem functions [60].
e integrity of an agroecosystem undergoing conversion relies on
synergies between plant diversity and the soil microbial community, to
optimize organic matter decomposition and turnover. Soils with high
organic matter and rich biological activity exhibit complex food webs
populated by benecial microorganisms that prevent pathogen
infection and insect pest incidence [58]. It may be argued that
diversied agroecosystems whose nutrient cycling is mediated by the
soil food web possess greater ecological stability, as well as resilience to
external perturbation [50]. Management should therefore be oriented
to enhance the ability of a crop plants to resist insect pests and diseases
by manipulating the biological properties of soils complemented by a
vegetational infrastructure that harbors natural enemies of pests as
well as pollinators [1]. Enhancing below-ground and above-ground
positive ecological interactions through integration of soil and pest
management practices constitutes a robust and sustainable path for
optimizing agroecosystem function and productivity.
Basing the conversion process on particular practices tends to
address components in isolation, focusing on the optimization of one
component (soil fertility, plant nutrition, crop growth, etc.) failing to
exploit the properties that emerge through the interaction of the
various farm components. Input substitution thus becomes primarily
reactive, shiing eorts to solving problems as they arise, ameliorating
symptoms rather than addressing root causes. Agroecologists regard
pest problems or nutrient deciencies as a symptom of a failure of an
ecological process (biological control or nutrient cycling) and thus
endeavor to nd out the root causes of such unbalance. Instead of
Citation: Nicholls CI, Altieri MA, Vazquez L (2016) Agroecology: Principles for the Conversion and Redesign of Farming Systems. J Ecosys
Ecograph S5: 010. doi:10.4172/2157-7625.S5-010
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J Ecosys Ecograph Global Climate Change ISSN:2157-7625 JEE, an open access journal
focusing on one particular component of the agroecosystem,
Agroecology emphasizes the interrelatedness of all agroecosystem
components and the complex dynamics of ecological processes. us
Agroecology is an alternative approach that transcends the use of
alternative inputs to develop integrated agroecosystems that do not
depend on external, o-farm inputs. e emphasis is on the design of
complex agroecosystems in which synergisms between biological
components replace inputs by promoting processes that through
proper management allow farmers to naturally sponsor the soil
fertility, productivity, and crop protection of their farming systems
[7,13].
References
1. Altieri MA, Nicholls CI (2004) Biodiversity and pest management in
agroecosystems (2nd edn.). e Harworth Press, Binghamton, New York,
USA, pp: 248.
2. iessen Martens JR, Entz MH, Wonneck MD (2015) Review :
Redesigning Canadian prairie cropping systems for protability,
sustainability, and resilience. Can J Plant Sci 95: 1049-1072.
3. Heinemann JA, Massaro M, Coray DS, Agapito-Tenfen SZ, Wen JD
(2013) Sustainability and innovation in staple crop production in the US
Midwest. Int J Agric Sustain 12: 71-88.
4. Landis DA, Gardiner MM, van der Werf W, Swinton SM (2008)
Increasing corn for biofuel production reduces biocontrol services in
agricultural landscapes. PNAS 105: 20552–20557.
5. Zhao ZH, Hui C, He DH, Li BL (2015) Eects of agricultural
intensication on ability of natural enemies to control aphids. Sci Rep 5:
8024.
6. Rosenzweig C, Hillel D (2008) Climate varibility and the global harvest:
Impacts of El Nino and other oscillations on agroecosystems. Oxford
University Press, New York.
7. Altieri MA (1995) Agroecology: e science of sustainable agriculture.
Agroforestry Systems 35: 111-115.
8. De Schutter O (2010) Report submitted by the Special Rapporteur on the
right to food. UN General Assembly. Human Rights Council. Sixteenth
Session, Agenda item 3 A/HRC/ 16/49.
9. Folke C (2006) Resilience: e emergence of a perspective for social
ecological systems analyses. Glob Environ Chang 16: 253-267.
10. Kremen C, Miles A (2012) Ecosystem services in biologically diversied
versus conventional farming systems: Benets, externalities, and trade-
os. Ecology and Society 17: 40.
11. Lotter DW (2003) Organic agriculture. J Sustainable Agric 21: 37-51.
12. Vandermeer J, Van Noordwijk M, Anderson J, Ong C, Perfecto I (1998)
Global change and multi-species ecosystems: Concepts and issues. Agric
Ecosyst Environ 67: 1-22.
13. Gliessman SR (1998) Agroecology: Ecological process in sustainable
agriculture. Ann Arbor Press, Michigan, pp: 356.
14. Altieri MA (2002) Agroecological principles and strategies for sustainable
agri-culture. In: Upho NT (ed.), Agroecological innovations: Increasing
food production with participatory development. Earthscan publication
Ltd., London, pp: 40-46.
15. Lamine C, Bellon S (2009) Conversion to organic farming: A
multidimensional research object at the crossroads of agricultural and
social sciences. A review Agron Sustain Dev 29: 97-112.
16. McRae RJ, Hill SB, Mehuys FR, Henning J (1990) Farm scale agronomic
and economic conversion from conventional to sustainable agriculture.
Advances in Agronomy 43: 155-198.
17. Rosset PM, Altieri MA (1996) Agroecology versus input substitution: A
fundamental contradiction of sustainable agriculture. Society & Natural
Resources: An International Journal 10: 283-295.
18. Gliessman SR (2010) Agroecology: e ecology of sustainable food
systems. (2nd edn.). CRC Press, Boca Raton, London, Newyork.
19. Altieri MA, Nicholls CI (2012) Agroecology: Scaling up for food
sovereignty and resiliency. Sustainable Agriculture Reviews 11: 1-29.
20. Altieri MA (2002) Agroecology: e science of natural resource
management for poor farmers in marginal environments. Agric Ecosyst
Environ 93: 1-24.
21. Timmermann C, Felix G (2015) Agroecology as a vehicle for contributive
justice. Agric Hum Values 32: 523-538.
22. Mader P, Fliessbach A, Dubois D, Gunst L, Fried P, et al. (2002) Soil
fertility and biodiversity in organic farming. Science 296: 1694-1697.
23. Li L, Shu-Min Li, Sun JH, Zhou LL, Bao XG, et al. (2007) Diversity
enhances agricultural productivity via rhizosphere phosphorus
facilitation on phosphorous-decient soils. Proceedings of the National
Academy of Sciences 104: 11192-11196.
24. Pimentel D, Hepperly P, Hanson J, Douds D, Seidel R (2005)
Environmental, energetic and economic comparisons of organic and
conventional farming systems. Bioscience 55: 573-582.
25. Ponisio LC, M’Gonigle LK, Mace KC, Palomino J, de Valpine P, et al.
(2015) Diversication practices reduce organic to conventional yield gap.
Proc R Soc B 282: 20141396.
26. Lithourgidis AS, Dordas CA, Damalas CA, Vlachostergios DN (2011)
Annual intercrops: An alternative pathway for sustainable agriculture.
Australian Journal of Crop Science 5: 396-410.
27. Vandermeer J (1992) e ecology of intercropping. Cambridge University
Press, New York.
28. Huang C, Liu QN, Stomph T, Li B, Liu R, et al. (2015) Economic
performance and sustainability of a novel intercropping system on the
north China plain. PLoS ONE 10: e0135518.
29. Zhang F, Li L (2003) Using competitive and facilitative interactions in
intercropping systems enhances crop productivity and nutrient-use
eciency. Plant and Soil 248: 305-312.
30. Malezieux E (2012) Designing cropping systems from nature. Agron
Sustain Dev 32: 15-29.
31. Andow DA, Hidaka K (1989) Experimental natural history of sustainable
agriculture: syndromes of production. Agric Ecosyst Environ 27: 447-462.
32. Vazquez LL, Matienzo Brito Y, Simonetti JA, Veitia Rubio M, Paredes ER,
et al. (2012) Contribution to agroecological systems design urban and
suburban ecological processes to favor production. Agricultura Oragnica
(Cuba) 18: 14-19.
33. Moonen AC, Barberi P (2008) Functional biodiversity: An agroecosystem
approach. Agric Ecosyst Environ 127: 7-21.
34. Risch SJ, Andow D, Altieri MA (1983) Agroecosystem diversity and pest
control: Data, tentative conclusions, and new research directions. Environ
Entomol 12: 625-629.
35. Andow D (1991) Vegetational diversity and arthropod population
response. Annual Review of Entomology 36: 561-586.
36. Tonhasca A, Byrne DN (1994) e eects of crop diversication on
herbivorous insects: a meta-analysis approach. Environ Entomol 19:
239-244.
37. Letourneau DK, Armbrecht I, Salguero Rivera B, Montoya Lerma J,
Jimenez Carmona E, et al. (2011) Does plant diversity benet
agroecosystems? A synthetic review. Ecol Appl 21: 9-21.
38. Boudreau MA (2013) Diseases in intercropping systems. Annu Rev
Phytopathol 51: 499-519.
39. Hiddink GA, Termorshuizen AJ, Bruggen AHC (2010) Mixed cropping
and suppression of soilborne diseases. In: Lichtfouse E (ed.). Genetic
Enginee ring, Biofertilisation, Soil Quality and Organic Farming.
Sustainable Agriculture Reviews, Springer Science+Business Media,
Dordrecht, e Netherlands, 4: 119-146.
40. Stone A, Scheuerell S, Darby H, Magdo F, Ray R (2004) Suppression of
soilborne diseases in eld agricultural systems: organic matter
management, cover cropping, and other cultural practices. In: Magdo F,
Weil RR (eds.)Soil organic matter in sustainable agriculture. CRC Press,
Boca Raton, Florida, USA, pp: 131-177.
Citation: Nicholls CI, Altieri MA, Vazquez L (2016) Agroecology: Principles for the Conversion and Redesign of Farming Systems. J Ecosys
Ecograph S5: 010. doi:10.4172/2157-7625.S5-010
Page 7 of 8
J Ecosys Ecograph Global Climate Change ISSN:2157-7625 JEE, an open access journal
41. Poggio SL (2005) Structure of weed communities occurring in
monoculture and intercropping of eld pea and barley. Agric Ecosyst
Environ 109: 48-58.
42. Liebman M, Dyck E (1993) Crop rotation and intercropping strategies for
weed management. Ecol Appl 3: 92-122.
43. Horwith B (1985) A role for intercropping in modern agriculture.
Biological Science 35: 286-291.
44. Willey RW (1979) Intercropping – its importance and its research needs
Part 1. Competition and yield advantages. Field Crop Abstracts 32: 1-10.
45. Natarajan M, Willey RW (1996) e eects of water stress on yields
advantages of intercropping systems. Field Crop Res 13: 117-131.
46. Marriott EE, Wander MM (2006) Total and labile soil organic matter in
organic and conventional farming systems. Soil Sci Soc Am J 70: 950-959.
47. Weil RR and Magdo F (2004) Signicance of soil organic matter to soil
quality and health. In Magdo F, Weil RR (eds.) Soil organic matter in
sustainable agriculture. CRC Press, Boca Raton, Florida, USA, pp: 1-42.
48. Liu B, Tu C, Hu S, Gumpertz M, Ristaino JB (2007) Eect of organic,
sustainable, and conventional management strategies in grower elds on
soil physical, chemical, and biological factors and the incidence of
Southern blight. Appl Soil Ecol 37: 202-214.
49. Hudson B (1994) Soil organic matter and available water capacity. J Soil
Water Conserv 49: 189-194.
50. Reganold JP (1995) Soil quality and protability of biodynamic and
conventional farming systems: a review. Am J Alternative Agr 10: 36-46.
51. Morris RA, Garrity DP (1993) Resource capture and utilization in
intercropping: water. Field Crops Res 34: 303-317.
52. Altieri MA, Nicholls CI, Henao A, Lana MA (2015) Agroecology and the
design of climate change-resilient farming systems. Agron Sustainable
Dev 35: 869-890.
53. Wall GJ, Pringle EA, Sheard RW (1991) Intercropping red clover with
silage corn for soil erosion control. Can J Soil Sci 71: 137-145.
54. Altieri MA, Ponti L, Nicholls CI (2012) Soil fertility, biodiversity and pest
management. In: Gurr GM, Wratten SD, Snyder WE, Read DMY (eds.)
Biodiversity and insect pests: Key issues for sustainable management.
John Wiley & Sons, Ltd, Chichester, UK.
55. Chaboussou F (2004) Healthy crops: A new agricultural revolution. Jon
Carpenter Publishing, Oxford, England, pp: 244.
56. Altieri MA, Nicholls CI (2003) Soil fertility management and insect pests:
Harmonizing soil and plant health in agroecosystems. Soil Till Res 72:
203-211.
57. Phelan PL, Mason JF, Stinner BR (1995) Soil-fertility management and
host preference by European corn borer, Ostrinia nubilalis (Hübner),
on Zea mays L.: A comparison of organic and conventional chemical
farming. Agric Ecosyst Environ 56: 1-8.
58. Hsu YT, Shen TC, Hwang SY (2009) Soil fertility management and pest
responses: A comparison of organic and synthetic fertilization. J Econ
Entomol 102: 160-169.
59. Phelan PL (2009) Ecology-based agriculture and the next green
revolution: Is modern agriculture exempt from the laws of ecology? In:
Bohlen PJ, House G (eds.) Sustainable agroecosystem management:
Integrating ecology, economics, and society. CRC Press, Boca Raton, FL,
pp: 97-135.
60. van Emden HF, Williams GF (1974) Insect stability and diiversity in
agroecosystems. Annu Rev Entomol 19: 455 -475.
61. Power AG, Flecker AS (1996) e role of biodiversity in tropical managed
ecosystems. In: Orians GH, Dirzo R, Cushman JH (eds.) Biodiversity and
Ecosystem Processes in Tropical Forests. Springer-Verlag, New York, pp:
73-194.
This article was originally published in a special issue, entitled: "Global Climate
Change", Edited by Fatih Evrendilek
Citation: Nicholls CI, Altieri MA, Vazquez L (2016) Agroecology: Principles for the Conversion and Redesign of Farming Systems. J Ecosys
Ecograph S5: 010. doi:10.4172/2157-7625.S5-010
Page 8 of 8
J Ecosys Ecograph Global Climate Change ISSN:2157-7625 JEE, an open access journal
... Agroecology, understood as "the ecology of food systems" (Francis et al., 2003) and "a systemic, transdisciplinary, participatory, and action-oriented approach" (Méndez et al., 2015) is-by systems thinking (Olson and Francis, 1995;Gliessman, 2015) and ecologically founded principles for selection of practices (Altieri and Nicholls, 1999;Gliessman, 2015)-a strategy for more sustainable management of the agroecosystems including improved quality and quantity of the food production, decreased use of synthetic pesticides and fertilizers, and mitigation of soil erosion (McIntyre et al., 2009;Nicholls et al., 2017). Since recently, French Polynesia is involved in an international program (the 11th European Fund for Development-FED in French) that aims to promote an agroecological transition and the development of organic farming (Service Public, 2018a). ...
... Then, we translated these six principles into 11 management practices (MP) that stood out as important to enhance the soil fertility and reduce soil erosion (MP1-MP6, Table 1), and to reduce or suppress pesticide use (MP7-MP11, Table 1) (Altieri and Nicholls, 1999;Wezel et al., 2014;Nicholls et al., 2017). ...
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In the context of climate change, French Polynesia is committed to increasing qualitatively and quantitatively local food production. In this regard, agroecology is perceived as a sustainable pathway to improve farming practices. This article proposes first a theoretical framework to analyze the proximity of farmers' management to agroecological principles. Second, it describes the current use of agroecological pest and soil management practices by French Polynesian farmers. And third, it explains which agronomic and socio-economic factors drive the implementation of agroecological practices. For this, qualitative interviews were conducted with 32 farmers on three islands, and statistical analyses were carried for correlation between the use of practices and socio-economic variables. Results show that French Polynesian farmers implement different soil and pest management practices that are in line with agroecological principles. Farmers scored better in terms of pest management with high plant diversity, implementation of crop rotations, and mechanical weed management. There is a significant influence of the “cropping system” and the “production system” (organic, integrated, and conventional) on the use of practices as well as proximity to agroecological principles. Identified pathways for an agroecological transition are implementing farmer to farmer knowledge exchange, farmer networks, and farm demonstrations as well as training of extension services staff.
... Its goal is to create biodiverse, resilient and fertile environments, use and recycle the nutrients and the energy of agroecosystems, while maintaining their self-sustaining capacity. Agroecological farming strives to achieve diversification at farm and/or landscape level, augment biological interactions and agroecosystem synergies as well as reduce dependence on agrochemicals and energy inputs (Altieri 2002;Nicholls, Altieri, & Vazquez, 2017). Agroforestry is defined as «a collective name for land-use systems and technologies where woody perennials (trees, shrubs, palms, bamboos, etc.) are deliberately used on the same land-management units as agricultural crops and/or animals, in some form of spatial arrangement or temporal sequence» (FAO, 2015). ...
... crop rotation, composting, cover cropping, etc.). They are, and will be, designed as Nicholls et al. (2017) define as the ultimate agroecological system: i.e. «an ecological infrastructure that through plot-to landscape-scale diversification, encourage[s] ecological interactions that generate […] essential ecosystem services' '. Finally, family farms must be designed as functional food systems that improve their economic and social sustainability. ...
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Over the last 30 years, extensive areas of Cerrado, the Brazilian savannah, have been converted to export-oriented agribusinesses. The social, environmental and economic impact of such large-scale land-use conversion is massive. To understand whether the current farming development in the Cerrado is sustainable, this study analyzes the sustainability performance of single farms applying the triple bottom line approach. Its aim is to assess the sustainability of soy, family and agroforestry farms. Fifteen farms were analyzed through the indicator-based sustainability assessment tool «RISE». The sustainability scores of RISE themes revealed that soy farms are economically sustainable, while their socio-environmental sustainability degree is rather critical. They scored lower than the other two farm types in all RISE themes except in the «economic viability» and «water use». Family farms and agroforestry are environmentally sustainable according to RISE.The sustainability degree of their social themes is either critical or scarcely positive mainly due to the high number of working hours and the low wage and income level. Looking at the economic sustainability, family farms reached a critical degree and agroforestry farms a barely positive degree. While the difference of sustainability performance between soy farms and the two others is large, it is minimal between agroforestry and family farms. RISE was a valid tool to assess with a moderate amount of data the sustainability performance of highly diverse farm types in the Cerrado.
... Its goal is to create biodiverse, resilient and fertile environments, use and recycle the nutrients and the energy of agroecosystems, while maintaining their self-sustaining capacity. Agroecological farming strives to achieve diversification at farm and/or landscape level, augment biological interactions and agroecosystem synergies as well as reduce dependence on agrochemicals and energy inputs (Altieri 2002;Nicholls, Altieri, & Vazquez, 2017). Agroforestry is defined as «a collective name for land-use systems and technologies where woody perennials (trees, shrubs, palms, bamboos, etc.) are deliberately used on the same land-management units as agricultural crops and/or animals, in some form of spatial arrangement or temporal sequence» (FAO, 2015). ...
... crop rotation, composting, cover cropping, etc.). They are, and will be, designed as Nicholls et al. (2017) define as the ultimate agroecological system: i.e. «an ecological infrastructure that through plot-to landscape-scale diversification, encourage[s] ecological interactions that generate […] essential ecosystem services' '. Finally, family farms must be designed as functional food systems that improve their economic and social sustainability. ...
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Over the last 30 years, extensive areas of Cerrado, the Brazilian savannah, have been converted to export-oriented agribusinesses. The social, environmental and economic impact of such large-scale land-use conversion is massive. To understand whether the current farming development in the Cerrado is sustainable, this study analyzes the sustainability performance of single farms applying the triple bottom line approach. Its aim is to assess the sustainability of soy, family and agroforestry farms. Fifteen farms were analyzed through the indicator-based sustainability assessment tool «RISE». The sustainability scores of RISE themes revealed that soy farms are economically sustainable, while their socio-environmental sustainability degree is rather critical. They scored lower than the other two farm types in all RISE themes except in the «economic viability» and «water use». Family farms and agroforestry are environmentally sustainable according to RISE. The sustainability degree of their social themes is either critical or scarcely positive mainly due to the high number of working hours and the low wage and income level. Looking at the economic sustainability, family farms reached a critical degree and agroforestry farms a barely positive degree. While the difference of sustainability performance between soy farms and the two others is large, it is minimal between agroforestry and family farms. RISE was a valid tool to assess with a moderate amount of data the sustainability performance of highly diverse farm types in the Cerrado.
... Agroecology is a key building block for food sovereignty (Nyéléni, 2007). The core design principles of agroecology include diversity, recycling, synergy, interactions, and efficiency (Nicholls et al., 2017). These synthesized principles are based on farmer practices, also known as farmer innovations, and are useful to characterize and re-design sustainable and resilient food and farming systems as whole, dynamic, and complex systems. ...
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Since March 2020, the COVID-19 pandemic propelled the “stay-at-home” policy worldwide under public health uncertainty, resulting in increased individualization, as well as an increased reliance or dependency on digital communication technology. Based on a review of existing literature alongside a reflection on personal fieldwork experiences, we aim to: (1) describe major elements of agroecological pedagogy, (2) explore adaptation pathways to combine digitalization and participatory action-learning, and (3) briefly discuss opportunities and challenges for agroecologists beyond COVID-19. Agroecological pedagogy is deeply embedded in the praxis, the scientific knowledge and ways of knowing (academic or not), and in the politics and agency of food movements. In line with Freire's liberation pedagogy, seeing what already exists (e.g., in: ecosystems, home-gardens, fields, farms, and watersheds) through participation and volunteering. Alongside a critical analysis to explain and explore certain phenomena, causes and consequences will likely result in the act leading to the implementation of transformative practices and novel designs that improve the state of any situation being addressed. Participatory action research/learning methods are strategic in agroecological pedagogy. Overall, the lockdown period led to increased societal digitalization of human interactions. During lockdown, however, the implementation of strategies for remote agroecology participatory action-learning were hampered, but not vanquished. Key changes to agroecology education projects “before” and “during” lockdown include an increased reliance on digital and remote strategies. Creative adaptations in the virtual classrooms were designed to nurture, deepen, and foster alternatives in favor of diverse knowledges and ways of knowing for food system transformations.
... The development of agroecosystems that can provide multiple ecosystem services with a reduced need of external inputs, requires management practices that foster ecological processes to enhance soil quality and crop productivity (Duru et al., 2015a;Nicholls and Altieri, 2017;Palomo-Campesino et al., 2018). Particularly in developing countries, the adoption of conservation management practices has been successful to maintain or increase crop yields while improving natural resource use efficiency (Pretty et al., 2006). ...
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The development of agroecosystems that can provide multiple ecosystem services with a reduced need of external inputs, requires management practices that foster ecological processes to enhance soil quality and crop productivity. We assessed the direct and indirect impacts of farmers' management practices on plant diversity, soil quality and crop productivity in coffee and pasture fields belonging to different types of farms: agroeco-logical, conventional, and large-scale. The study was carried out in twelve farms in the Zona da Mata, Brazil. For each of the total of 24 fields (twelve pastures and twelve coffee) we recorded 41 variables associated with management practices, indicators of plant diversity (taxonomical, structural and functional diversity) and soil quality (biological, chemical and physical properties). The direct and indirect effects of management on plant diversity, soil quality and in the case of coffee, crop productivity, were assessed using structural equation models. In the case of pastures, we found that increased plant diversity due to agroecological management resulted in higher soil quality, probably due to higher soil litter cover and plant structural heterogeneity. Yet, practices presented in the agroecological farms also had a direct negative effect on soil quality, which indicates that increased plant diversity in pastures needs to be combined with other agroecological management practices than currently adopted. In the case of coffee, we show that despite the higher weeding intensity and higher use of external inputs in large-scale and conventional coffee farming systems, these practices did not result in increased soil quality or coffee productivity as compared to agroecological systems. In contrast, agroecological coffee management was associated with increased plant diversity, which, in turn, was positively associated with soil microbial biomass carbon. Our results highlight a causal pathway of agroecological management leading to increased plant diversity and, in turn, maintenance or increase in soil quality. While no causal link between agroecological coffee management and coffee productivity could be demonstrated, the biodiversity-mediated pathway resulted in similar coffee productivity in agroecological farms as compared to conventionally managed farms, which relied on pesticides and higher inputs of chemical fertilizers. We conclude that agro-ecological practices can be efficient to maintain satisfactory crop yields and soil fertility without the need of intensive use of external inputs and weeding.
... However, after several decades of intensive use, these inputs have been found to have negative effects on the natural environment and human health, raising questions regarding the sustainability of these production systems (Tilman, 1998). Alternative systems have been proposed by some researchers, farmers and consumer movements, such as agroecology based on natural resources, biological processes and agrobiodiversity within farms and territories (Gliessman, 2015;Nicholls et al., 2017). Although politicians and citizens are increasingly sensitive to the damage caused by conventional agriculture, only a minority of farmers have adopted alternative practices up to now (Geiger et al., 2010;Nave et al., 2013). ...
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