Download The contribution of Portuguese agriculture to the climate

ADVANCES in CLIMATE CHANGES, GLOBAL WARMING, BIOLOGICAL PROBLEMS and NATURAL HAZARDS
The contribution of Portuguese agriculture to the climate change,
mitigation and adaptation strategies for the sector
CORINA CARRANCA
INRB, I.P./INIA
Unidade de Ambiente e Recursos Naturais
Quinta do Marquês, Av. República, Nova Oeiras, 2784-505 Oeiras
CEER, Instituto Superior de Agronomia, Tapada da Ajuda, 1349-017 Lisboa
PORTUGAL
e.mail: [email protected]
Abstract: - Agriculture in Portugal contributes for less than 10% of total greenhouse gas (GHGs) emissions,
where 34% comes from methane (CH4) in animal husbandry, 64% comes from nitrogen (N) oxides (NOx and
N2O) by the intensive use of mineral fertilizers, the incomplete nitrification and denitrification processes, the
waterlogged rice fields, the addition of organic compounds to the soil, the drip fertigation, the N2 fixation by
legumes, particularly, the pastures, and the sediments, by the alternate wetting and drying processes and the
presence of soil organisms such as worms. Animal husbandry is the main responsible (71%) for total emission
coming from agriculture, particularly the dairy cows housed. Methane emissions from the animal housing are
mainly caused by enteric fermentation. During storage and after spreading of farmyard manure in the soil
substantial differences concerning CH4 and N2O emissions occur with composted and anaerobically stacked
farmyard manure. In agriculture, forests are the main responsible for CO2 emission (4 Mt CO2 equivalent year1
) by the respiration process, and the double amount can be reached in presence of fires. However, forests have
an important role on CO2 capture during the photosynthetic process, by C accumulation in the plant biomass
and soil organic matter. The Portuguese forest can sequester about 80 t CO2 ha-1 year-1 and contributed to about
18% of C sequestration in 2010. The eucalyptus has a very efficient capacity to use water and nutrients and can
accumulate C in the biomass and soil more efficiently than other plant species in temperate climate. Microbial
activity is also responsible for CO2 emissions, particularly under soil disturbance. This is the case of pastures
conversion to annual crops. On the other hand, if soil conservation practices have been used, such as for
permanent pastures, C sequestration in the soil is appreciable. “Montado” is a Portuguese extensive farming
system consisting of cork and holms-oak trees, several shrubs and improved pastures. This is a very sustainable
agricultural system where pasture may consist of biodiverse crops with more than twenty species and include
several legumes. They can sequester more than 4 t C ha-1 year-1, particularly in the soil since the crops are used
for animal feeding (-4.5 t C km−2 year-1). Supposing an increase from 10 to 30 g organic matter kg-1 soil, an
accumulation of 33 t C ha-1 in a 15 cm layer is expected, corresponding to a sequestration of the order of 128 t
CO2 ha-1. These data show that 200,000 ha of permanent pastures will largely meet the Kyoto Protocol
Commitment (1997). About 80% of cultivated plants can be associated with mycorrhizal soil fungi. This
symbiosis allows a better performance and health for most efficiently mycorrhized plants, particularly under
biotic and abiotic stress, such as drought, high temperatures, saline and contaminants. These plants can capture
more CO2 from the atmosphere by the photosynthetic process, producing higher levels of photo assimilates
which are exuded by the roots enriching the mycorrhizosphere and contributing for the C sequestration.
Key-Words: -arable crop, forest, greenhouse gases, impact, modeling, nutrient and water use efficiency,
productivity, rainfall, soil microbial diversity, temperature.
atmospheric pollutants such as volatile organic
compounds (VOCs), nitrogen oxides (NOx) and
other ozone (O3) precursors must also be
investigated to better understand, in the light of
climate change, the continuously increasing of O3
background concentrations and the contribution
from changing biogenic and anthropogenic sources.
Concomitant increases in the biogenic gases
methane (CH4) and NOx have been observed
(Brouder and Volenec, 2008). Extreme events have
been registered worldwide, namely the high
temperatures, water deficit and fires in Russia, the
intensive rainfall events in central and east Europe,
1 Introduction
Climate change variables including precipitation
(amount and distribution), temperature and
atmospheric carbon dioxide (CO2) concentration
are expected to alter agricultural productivity
pattern worldwide. Carbon is a plant nutrient and
CO2 atmospheric enrichment has the potential to
enhance
plant
productivity
through
the
photosynthetic process. Higher global temperatures
and altered precipitation patterns are expected to
accompany the higher CO2 levels and these factors
may lessen or negate any production (Brouder and
Volenec, 2008). The chemical transformations of
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ADVANCES in CLIMATE CHANGES, GLOBAL WARMING, BIOLOGICAL PROBLEMS and NATURAL HAZARDS
the floods in India and Pakistan, and the landslides
in China.
The actual main challenge is to attack the
origin of the problem (mitigation), i.e., to reduce
the anthropogenic greenhouse gases (GHGs)
emissions and prepare the society for the
biophysics and socio-economic impacts of climate
change (adaptation). European Union (EU) defined
climate change as a priority area for research,
innovation and development in agriculture.
European Union put emphasis on prediction of
climate ecological, earth and ocean systems
changes, on tools and on technologies for
monitoring, preventing and mitigating of
environmental pressures, risks including on health
and for the sustainability of the natural and manmade environment, and adaptation strategies.
Models should include climate projections, the
hydrological and biogeochemical cycles, the
stratosphere and troposphere chemical interactions,
the interactions between climate and aerosols, the
representation of land surface processes, the
interactions between climate and ecosystems, the
improvement of the representation of cryospheric
processes, the sea level change, critical processes in
ocean and atmosphere interactions, and the
reduction of bias corrections at the interface
between regional climate models and climate
impact models.
Studies on global climate change and mineral
nutrition remain relatively sparse, with nitrogen (N)
being the primary focus of research. Existing
literature reviews have examined N and climate
change emphasizing the soil biodiversity (Swift et
al., 1998; Chapin, 2003; Carranca et al., 2009a,b),
water cycling (Pendall et al., 2004; Gonçalves et
al., 2006), root uptake kinetics (BassiriRad, 2000)
and soil C/N cycling in extreme environments
(Hobbie et al., 2002). The potential for global
climate change factors to influence the
physiological use efficiency of plant nutrient and
nutrient availability and transport through soil and
across root membranes are new questions
addressed. Experimentation has not found
conclusive evidence that physiological plant
nutrient use efficiency is altered in high CO2
environments (Brouder and Volenec, 2008).
Research should explore the stress on
vegetation and the impact on biomass including soil
organic matter (OM). Scientifically sound
thresholds for protecting plant ecosystems, as well
as soil biota from atmospheric pollutants and for
maintaining productivity and the carbon (C) sink
strength should be developed.
Schulp et al. (2008) estimated that the EU-27
will sequester 90-111 Tg C year−1 in 2030, in the
terrestrial biosphere. In three of the four scenarios
used in the Land Use Change (LUC) model, they
found that net C sequestration will increase, mainly
due to a decrease in cropland area.
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1.1 Greenhouse gases and climate change
The current concentrations of GHGs are believed to
have already altered global climate and there is
some evidence that warming has negatively
impacted crop yield. The rate of increase in GHGs
concentrations is expected to accelerate and a CO2
level of 550 µmol mol-1 can be reached by 2050
(Raven and Karley, 2006). Likewise, rate of
increase in temperature within the next century is
supposed to be markedly higher than the changes
that occurred in the past. It is advisable to stabilize
the CO2 concentration at a maximum of 500 µmol
mol-1 in order to stabilize the global temperature
rise at 2–3 ºC during the XXI century.
Temperature records from the northern
hemisphere showed a temperature rise of
approximately 0.6 ºC within a 150-year period
(Mann et al., 1998; Brouder and Volenec, 2008). In
the XX century, mean air temperature in Portugal
showed three patterns of variation: an elevation in
the 1910-1945 period, followed by a reduction by
1946-1975, and a more accelerated increase in the
1976-2000 period. In the last period of this century,
the minimum temperatures have risen, reducing the
temperature range. In this period, mean temperature
in the Iberian Peninsula increased by 1 ºC. In the
Portuguese continent, rainfall decreased in
February and March.
Schlenker et al. (2006) reported that
temperature will increase from 2.0 to 2.4 ºC
between 2020 and 2049 in USA relatively to the
present conditions, and can dramatically increase
(3.6 to 7.4 ºC) between 2070 and 2099. According
to Southworth et al. (2000), the mean annual global
surface temperature is projected to increase 1-3.5
ºC by 2100, but unlike CO2 the magnitude of
temperature increase will vary regionally and will
be accompanied by altered precipitation pattern
(Brouder and Volenec, 2008).
SIAM, SIAM II and CLIMAAT II Portuguese
models for climate change for the 2080-2100
period estimated a significant increase in the mean
air temperature, with an increase of about 4 ºC for
the maximum temperature in summer in coastal
areas and 7 ºC in the interior, and an increase of
heat waves frequency and intensity, fire risks, and
land-use changes. Precipitation in the mainland will
be reduced by 100 mm, especially in spring,
summer and autumn, with an increase in winter. In
Madeira and Azores islands, temperature will
increase more moderately (1-3 ºC).
Temperature has been considered as an
important ecological factor that determines a
variety of structural and functional characteristics
in managed and natural ecosystems, but the exact
mechanism for temperature-induced changes in
nutrient uptake capacity is not clearly understood
(BrassiriRad, 2000). Potentially, if soils warm as a
result of climate change, maintenance costs of roots
and nutrient availability may increase and
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must involve the whole society and requires a
coordinated strategy in Europe.
contribute to higher rates of root turnover, which is
a strong nutrient sink for most plants, except the
annual crops where root turnover is not an
important issue even in a CO2 enriched atmosphere
(Gill and Jackson, 2000; Norby and Jackson, 2000).
Across Europe, average wheat (Triticum
aestivum L.) yields have markedly increased since
the early 1960s, but rates of increase have been
slower in southern countries (e.g. Portugal and
Spain) when compared with the United Kingdom
and France reflecting the impact of the warming
and drought since the 1990s (Schär et al., 2004;
Brouder and Volenec, 2008).
IPPC (2007) identified the Mediterranean
region and south Europe in particular, as one of the
most vulnerable regions to climatic change, with
high temperatures, water deficit, lower crop
productivity, higher forest fires frequency, and
higher incidence of human diseases caused by the
heat waves. Such changes will have marked effects
on soil biology including plant growth and
physiological characteristics (shoots and roots).
Droughts are increasingly being observed in
many regions of Europe, requiring innovative
science-based approaches to evaluate the
complexity of environmental and socio-economic
impacts and people's vulnerability. In the European
context, it is essential to improve the understanding
of drought processes and occurrences, develop
innovative drought indicators and methodologies
for reducing and monitoring the vulnerability of
drought-related risks and their impacts to society
and the environment, in particular in water stressed
areas, and modeling, forecasting and monitoring,
taking into considerations different European geoclimatic regions.
The first objective of EU policy for climate
change is, through research, to provide integrated
solutions for action on mitigation of, and adaptation
to climate change in order to respond to global
challenges and the EU's ambitious commitment to
combating climate change. Research will improve
the estimation of impacts and provide scientific and
policy advice on mitigation and adaptation options.
Land-use and forestry changes, as well as urban
areas and coastal zones will be studied for
adaptation needs.
The second EU’s objective, again through
research, is to support eco-innovation for ecoefficiency in society. The transformation to
sustainable societies implies the development and
availability of technologies, products and services
that help to minimize the environmental "footprint"
of all human activities through energy and resource
efficiency.
The third EU’s objective, still through
research, is to provide a systemic approach for
governance in a changing environment. A transition
towards economic and environmental sustainability
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2 The contribution of Portuguese
agriculture to mitigation
Mitigation is the process to reduce or eliminate the
causes of climate change. The Portuguese Program
for Climatic Changes (PNAC) established a 52%
reduction of CO2 emission of anthropogenic origin
(1.1 Mt CO2) by 2010 comparing to 1990, but this
objective was not fulfilled. The new challenge is to
reduce anthropogenic CO2 emission by 40% in
2020 (Carranca, 2010).
The Portuguese agriculture is conditioned by
European Common Agriculture Policy (CAP),
which integrates environmental protection,
potential areas for agriculture, and farmers’ income
and economic welfare. It contributes for less than
10% of total GHGs emissions (2% by excluding the
agro-industry), where 34% comes from CH4 in
animal husbandry, and 64% from N oxides (NOx
and N2O) by the intensive use of mineral fertilizers,
the incomplete nitrification and denitrification
processes, the waterlogged rice fields, the addition
of organic compounds to the soil, the drip
fertigation, the N2 fixation by legumes, particularly
the pastures, animal husbandry, and the sediments,
by the alternate wetting and drying processes and
the presence of soil organisms such as worms
(Carranca, 2010).
Animal husbandry is the main responsible
(71%) of total emissions coming from agriculture,
mainly as CH4, particularly from the dairy cows
housed, but also by direct grazing. Methane
emission from the animal housing is mainly caused
by enteric fermentation. Feed additives can alter
rumen environment, potentially changing the end
products of fermentation. During storage and after
spreading of farmyard manure in the soil,
substantial differences concerning CH4 and
NO+N2O emissions occur with composted and
anaerobically stacked farmyard manure.
Studies on GHGs (NOx, CH4, VOCs) fluxes
from paddy rice fields in Portugal have been run for
mitigation and to establish good agricultural
practices.
In agriculture, forests are the main
responsible for CO2 emission (4 Mt CO2 equivalent
year-1) by the respiration process. The double
amount can be reached in presence of fires.
Portuguese forests occupy 38% of total area
(Fig. 1), where most part (85%) is private, 3% is
public and 12% belongs to the local communities.
Eucalyptus stands (E. globulus L.) represent 21%
of the total forest area and CO2 emission can
amount to 67 kt CO2 year-1 (Dias et al., 2007).
Portugal made the commitment of reducing total
CO2 emission by 7.6-8.8 Mt by 2012.
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ADVANCES in CLIMATE CHANGES, GLOBAL WARMING, BIOLOGICAL PROBLEMS and NATURAL HAZARDS
more than twenty crop species, including several
legumes.
However, forests have an important role on
CO2 capture during the photosynthetic process and
C accumulation in the plant biomass and soil OM
(mitigation). The Portuguese forest can sequester
about 80 t CO2 ha-1 year-1 and contributed to about
18% of C sequestration by 2010 (Carranca, 2010).
Fig. 2. A partial view of the extensive agricultural
system “montado” (oak and pasture), in Portugal.
This system can sequester more than 4 t C
ha-1 year-1, particularly in the soil, since pastures
are used for animal feeding (-4.5 t C km−2 year-1,
indicating the crop removal) (Schulp et al., 2008;
Carranca, 2010; Carranca et al., 2010). Supposing
an increase from 10 to 30 g OM kg-1 soil by
converting the natural pasture into improved
pasture, an accumulation of 33 t C ha-1 in a 15 cm
layer is expected, corresponding to a sequestration
of 128 t CO2 ha-1 (Carranca, 2010). These data
show that 200,000 ha of permanent improved
pastures would largely meet the Kyoto Protocol
Commitment (1997) in Portugal.
Microbial activity in soil is responsible for
CO2 emission by respiration, particularly under soil
disturbance. This is particularly relevant in the case
of conversion of forests to pastures or croplands, or
pastures conversion to arable land. The increase of
winter temperature in south Europe will also
increase soil microbial respiration thus reducing
sequestered C and increasing the CO2 emission.
Soil conservation practices used, for instance, for
permanent pastures, will sequester appreciable
amounts of C in soil (mitigation practice).
Legumes
are
important
crops
in
Mediterranean regions and can fix most plant N
from the atmosphere through the symbiotic process
with the generically called Rhizobium bacteria.
Atmospheric N2 is a renewable resource and its use
in the symbiosis for bacteria to obtain energy acts
as an indirect clean energy source, reducing the use
of mineral N fertilizer on legume nutrition and the
use of fossil energy for processing mineral
fertilizers. Legumes are recommended crops for
intercropping with non-legumes such as grasses,
fruit and olive trees, vineyards, pastures and forests
since they transfer nutrients to the non-legumes.
Symbiosis efficiency is improved in
mycorrhized host plants. If both legume and nonlegume plants show mycorrhizal hyphae, a strong
contribution to C sequestration in the soil can
occur. About 80% of cultivated plants are
colonized by mycorrhizal soil fungi [micorrhizal =
Fig. 1. Evolution of Portuguese forest in the
mainland (103 ha) (Source: MADRP, 2007).
The eucalyptus has a very efficient capacity
to use water and nutrients and can accumulate C in
the biomass and soil more efficiently than other
plant species in temperate climate (Alves et al.,
2007; Carranca, 2010). In the soil, the C content is
higher than in oak (Quercus sp.) soils, although the
degree of humification is similar (Madeira, 1986;
Madeira et al., 1989; Carranca, 2010). However,
the presence of humic and fulvic acids is higher in
eucalyptus soils (42%) comparing to other tree
species (29-32%).
Eucalyptus forms endo- and ectomycorrhiza.
A few plant genera are able to support both
mycorrhizal types and give the tree the high
efficiency for water and nutrient absorption.
Arbuscular mycorrhizal (endo-) produces glomalin
(a heat-stable hydrophobic glycoprotein which
prevents the fungi hyphae from desiccating) that
gives a better soil structure and enriches the soil C
pool (glomalin contains 30-40% C). This protein
lasts for years in the soil and may be in the slow or
recalcitrant soil C fraction (Rillig et al., 2003).
Pools of glomalin are responsive, even in the shortterm, to ecosystem perturbation, such as elevated
atmospheric CO2 concentrations, warming, and
various agricultural management practices and can
be used as a soil quality indicator (Rillig et al.,
2003). Ectomycorrhiza also probably influences the
soil aggregate stability by their ability to produce
hydrophobin (cystein enriched proteins expressed
only by filamentous fungi). They form a
hydrophobic coating on a surface.
“Montado” is an extensive agro-forest
farming system at south Portugal consisting of cork
and holms-oak trees, several shrubs and natural or
improved pastures (Fig. 2). This is a very
sustainable agricultural system where the improved
pastures may consist of biodiverse pastures with
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ADVANCES in CLIMATE CHANGES, GLOBAL WARMING, BIOLOGICAL PROBLEMS and NATURAL HAZARDS
comprises a substantial fraction of soil OM in many
systems, and aspects of the biology and chemistry
of mycorrhized hyphae can influence the C cycling
in soil (Norby and Jackson, 2000; Carranca, 2010).
Farrar and Jones (2000) reported that the
presence of higher CO2 concentration and
temperature will produce bigger plants, with bigger
root systems as a consequence of their size, but
with little or no change in C partitioning to them
(Table 1). However, as these large plants have
more demand for water and nutrients, and the soil
is relatively depleted in these resources as a
consequence, there will be more growth of
(mycorrhized) roots relative to shoots directed by
mechanisms as yet unknown, and if soil nutrients
are low there might also be more exudation from
roots and C transfer to mycorrhiza and the soil, but
these effects of elevated CO2 will be indirect.
myke (soil fungi) + rhiza (fine roots)]. This
symbiosis is ubiquitous and allows a better
performance and health for most plants, particularly
under biotic and abiotic stresses such as drought,
high temperature, saline and contaminants (Cruz
and Carranca, 2010). Mycorrhized plants capture
more CO2 from the atmosphere through the
photosynthetic process (mitigation), producing
higher levels of photo assimilates which are exuded
by the roots to the soil enriching the
mycorrhizosphere and contributing to atmospheric
C sequestration (mitigation) (Carranca, 2010).
Fig. 3. Root nutrient uptake in response to CO2
concentration and soil temperature (Source:
BrassiriRad, 2000).
Table 1. Growth and root metabolism of barley at
14-days after germination under two CO2 levels
(Source: Farrar and Jones, 2000)
Variables
Dry weight (mg)
Root weight ratio
Rate of elongation of
seminal axis (cm h−1)
Number of nodal roots
Rate of lateral root
production (h−1)
Carbohydrate content of
seminal axes (mg g−1 FW)
Respiration of seminal
axes (nmol g−1 s−1)
Carbohydrate content of
root tips (mg g−1 FW)
Respiration of root tips
(pmol per tip s−1)
FW=fresh weight.
(larger picture can be found at the end of the
article)
Fig. 3 shows the root nutrient uptake kinetics
in function of CO2 concentration and soil
temperature. BrassiriRad (2000) reported that plant
N uptake response to elevated CO2 concentration
was more closely correlated with root physiology
capacity under low N availability (mycorrhizal
effect), but correlated more strongly with root
biomass under relatively high N content.
Mycorrhized plants are more efficient to absorb
water and nutrients (Cruz and Carranca, 2010).
It is commonly accepted that an important
determinant of plant and ecosystem responses to
elevated CO2 concentrations is plant nutrient status.
Therefore, knowledge on root characteristics that
influence nutrient uptake and their response to the
high CO2 concentrations is critical in accurately
predicting the long-term plant and ecosystems
responses to CO2 enrichment (BrassiriRad, 2000).
Temperate grasslands allocate between 24% and
87% of net primary production belowground. In
forests, belowground net primary productivity
typically accounts for 30-50% of total net primary
production (Gill and Jackson, 2000). This shows
the contribution of roots and mycorrhizal hiphae to
soil OM and C sequestration. Mycorrhizal tissue
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CO2 concentration (ppm)
350
700
154
0.31
0.12
222
0.31
0.18
3.4
1.1
5.8
1.8
3.2
4.0
2.7
3.9
17.3
37.9
22
33
Trees with reduced absorbing fine roots have
a great potential for efficient colonization by soil
fungi. This is the case of ‘Rangpur’ rootstock for
citrus, which is the most used rootstock in Brazil by
its great potential to support drought stress.
The main factors that affect mycorrhizal
efficiency are plant type and abundance and
diversity of soil fungi, which in turn depend on: i)
soil disturbance, which destroys the plant roots and
spores and disturbs microbial activity; ii) long
duration of water scarcity, which reduces fungi
abundance and diversity; iii) the presence of
contaminants or inhibitors, such as pesticides and
heavy metals, which reduce the abundance of
fungi; iv) crop rotation, which increases soil fungi
abundance and diversity; v) intensive fertilization
and irrigation, which reduce colonization or
mycorrhizal efficiency.
The evaluation of impacts of climate change
on Portuguese agriculture was primarily based on
simulating models such as DSSAT (Decision
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Support Systems for Agro-technology Transfer)
and CERES WHEAT (wheat) and CERES MAIZE
(maize) (Santos et al., 2001). It was shown that
higher CO2 concentration may increase crop
productivity and water use efficiency, but higher
temperature will induce faster growth rate and
higher water requirement (Santos et al., 2001).
There is a general agreement that both single-leaf
and canopy photosynthesis by C3 plants will
increase more than that of C4 plants as atmospheric
CO2 concentration increases, partly due to an
inhibition of photorespiration by CO2 in C3 plants,
a process that does not impact photosynthesis of C4
plants (Brouder and Volenec, 2008). These plants
have higher photosynthetic rates than C3 plants and
prefer high temperatures. Frequently, they are
referred as “warm-season” plants [e.g. maize (Zea
mayz L.), sorghum (Sorghum bicolor L. Moench),
sugarcane
(Saccharum
officinarum
L.),
bermudagrass (Cynodon dactlylon L.)]. This shows
that C3 plants are more responsive to the CO2
increase than C4 plants. Water use efficiency of C4
plants is often twice that of C3 plants, sometimes by
stomata closure (Brouder and Volenec, 2008). The
elevated CO2 concentration reduces stomata
conductance in many plant species.
Crop productivity is also a function of soil
quality. A good soil is an important sink for C
sequestration (1.5 Gt C year-1), equivalent to
two/three times the atmospheric CO2 level
(Gallego, 2001; Carranca, 2010). Portuguese
agricultural soils can accumulate 47 t C ha-1 in a 30
cm layer. This natural resource is subject to
degradation (erosion, loss of OM and biodiversity,
acidification, contamination, salinization, flooding,
sealing, landslides, fires), and is not renewable in a
human scale [1000-10000 years to completely form
a 30 cm soil (Haberli et al., 1997; Carranca, 2010)].
Most Portuguese soils (90%) are poor in OM,
showing a high to moderate erosion risk (69%),
with an erosion rate of 4.5 t ha-1 year-1 (Carranca,
2010). Erosion and loss of OM are due to extreme
rainfall events, high mineralization rates influenced
by the high air temperature, soil type and slope, and
wrong agricultural practices, such as tillage, fallow,
intensive grazing, reduced crop rotations.
Good agricultural practices to increase soil
OM content (e.g. cultivation of permanent or
annual pastures, soil conservation practices,
biological production, maintenance of soil cover,
efficient mycorrhization, introduction of legumes in
crop rotations with long duration, and as
intercropping) should be encouraged. Bare soils can
be more than 5 ºC warmer with much higher
surface evapotranspiration than residue covered
soils, resulting in altered rates of mineralization and
nutrient diffusion (Brouder and Volenec, 2008).
3
Adaptation
of
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agriculture to climatic changes
Adaptation is a process to reduce the negative
impacts of climate change in different socioeconomic sectors (e.g. agriculture) and biophysics
systems. Previous to adaptation strategies, the
impacts of climate change should be identified.
Adaptation to climate change is planned by local or
national government, or spontaneous, i.e., done
privately without government. In Portugal,
adaptation strategies include: i) information and
research; ii) vulnerability reduction and
responsiveness; iii) participation, awareness and
dissemination; iv) international cooperation.
Climate will change but details regarding
impact on agriculture remain vague and it is not
easy to predict future food supply. A first
requirement is mapping the land-use and climate
change. Crop models are also major tools for
studying climate change scenarios in agriculture.
Developing dynamic models is recommended for
annual and perennial crops to evaluate
physiological rates (stomata conductance and
photosynthetic processes, water and nutrient use
efficiency, etc.), root response to global change
(e.g. root biomass, morphological characteristics,
hydraulic conductivity kinetics, mycorrhizal), new
pests and diseases, and adaptation strategies for
fruit and olive trees, vineyards, forest trees. Ver
Sofo et al (2005) nas micorrizas
There are a few models that can simulate
climate data for the future. One of those is
HadRM3, a regional model from Hadley Centre,
which generates temperature data, from emission
scenarios data (Santos et al., 2001; Almeida, 2009).
The results of this model showed an increase of
temperature in Portugal for the years to come. To
estimate ecological fitness, in the present and in a
future scenario, a system named SISAP (System for
Crop Adaptation) was developed in Portugal. This
program crossed soil and weather requirements of
crops with other environmental data. Results
showed that crops can grow in the Alqueva
irrigation area at south Portugal with reduced to
medium productivity. When comparing the results
for the present and the future scenario, it is easy to
understand that in the future all crops will achieve
higher productions, due to the higher temperatures
and CO2 concentrations. The only exception from
tested crops was kenaf (Hibiscus cannabinus sp.),
where future will bring the worst results. A large
perennial C4 grass (Miscanthus sp.), which can be
used as a biodiesel crop, was the most interesting
plant from an ecological standpoint for this area.
The expected lower amount of rainfall in
spring and summer in Portugal will increase
irrigation water requirements and may increase the
water stress by rainfed crops, although the
anticipation of sowing time may reduce this effect.
SIAM II and HadCM3 models advised that sowing
date should be altered for a better productivity.
Portuguese
53
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ADVANCES in CLIMATE CHANGES, GLOBAL WARMING, BIOLOGICAL PROBLEMS and NATURAL HAZARDS
Models such as ANIMO, CANDY, CENTURY,
DAISY, GEFSOC, HERMES, NCSOIL, NTRM, RothC,
SOILN, SUNDIAL, etc. have been tested for OM
Sowing date should be anticipated from 1
November to 15 October for wheat (rainfed crop)
and from 1 April to 15 March for maize (irrigated
crop) (Santos et al., 2001). Tuber crops (sugarbeet,
potatoes) will beneficiate from higher temperatures
and CO2 levels. Irrigated crops will be less
responsive to climate variability comparing to
rainfed crops. It is supposed that most crops will
move to the north part of the country, but possibly
the slow-growing plant species like oak trees will
move very slowly. Northern European countries
will show better conditions for agriculture
production in future.
Carbon dioxide emission increases by
increasing temperature through the respiration
process. This emission should be reduced but
avoiding the inhibition of cell respiration (Correia,
2010). The reduction of CO2 must happen for
hundred years since the gas resilience in the
atmosphere is about a hundred years (Carranca,
2010). C3 plants may accrue a direct benefit from
an atmospheric CO2 enrichment. According to
Brouder and Volenec (2008), if plants produced
under elevated CO2 are simply bigger, but
otherwise the same in their gross nutrient content
per unit biomass, then present-day nutrient balance
calculations for fertilizer recommendations will
remain applicable. In crop species that have been
extensively improved for agriculture, nutrient
concentrations, especially in grain, can be relatively
constant when yields are not limited by other
factors.
A general model was developed in Visual
Basic for fruit trees (Melo e Abreu, 2010). This
model has been used to study changes in flowering
dates and yield based on Portuguese climate change
scenarios. Some models indicated a possible
extension for vineyard areas, but there are some
CAP restrictions.
Plant breeding is also an important tool for
better adapted new varieties and cultivars, and
regional cultivars to drought stress and high
temperature, namely by shortening or enlarging the
growth cycles, and for a better nutrient and water
use efficiency. At south Portugal, where water
availability is scarce, crops should be replaced by
others with a better capacity for water use.
New pests, diseases and weeds will probably
appear under the climate change, but the
occurrence of fungi diseases such as oidium and
mildew may be reduced by the lower spring
rainfall. Tropical diseases and pests may increase.
Desertification process will tend to be
intensified by climate change. According to the
Portuguese Commission for Climatic Changes
(2002), robust models should be developed to
include C sequestration by forest and changes in
land-use, including the fires. In Europe, data basis
on C sequestration in forests are mostly empirical.
ISSN: 1792-6173 / ISSN: 1792-619X
dynamics in several agro-ecosystems, but only in a
local scale. Very few have been used in a regional,
national or continental scale (Carranca, 2010).
Several problems occur with these models in a
broad scale, namely the historical land-use, the OM
dynamics in deep layers, etc. The CENTURY and
RothC simulation models were calibrated and
validated for different ecosystems, including
different soil types in temperate climate. The LUC
model to evaluate C sequestration in a global scale
combines the global economic model (GTAP), the
land-use and environmental variability model
(IMAGE), and the Dyna-Clue model for spatial
variability. Using this LUC model, Schulp et al.
(2008) evaluated four scenarios for EU-27 and
concluded that climate change by 2030 will not be
significant. They stated that intensive cropping will
reduce C sequestration up to 2%, but moving from
cultivation to abandonment or permanent pastures
it will increase by 9-16%. They recommended that
only young forests should be replaced, not the old
ones with high biomass and accumulated C.
The promotion of extensive livestock,
particularly ruminants, taking into account the
persistence of pastures and the use of biodiverse
and irrigated pastures are also recommended
options for the present climatic conditions.
4 Acknowledgements
The author thanks Dr. Pedro Reis (INIA) and
Prof. J. beltrão (Univ. Algarve) for their
contribution on manuscript revision.
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