Various climatic factors relative to disease should
include an examination of the variability in climate of the location in
question for at least the past 10-20 years. Human knowings about climate and
willingness to use that understanding in societal decision-making change over
the globe [30]. It is possible that climate variations over space is more
essential to human development than climate variations over time. This is
suggested by the fact that regions with the most changing climates are near the
tropics and that countries in these areas are usually less able to deal with
effects of unfavorable weather than that of the countries in temperate regions.
In some countries, the internal changes of yields are greater than those
predicted for other countries over much longer periods of time [31]. Short-term
climate changes may have long-term consequences in some ecosystems like
forests. The impact of change may depend upon the type of variation that
occurs. Particularly, in marginal areas, a large biological effect is caused by
a small change in frequency of extremes. There are large differences between
temperate regions and tropic region with regard to the effect of precipitation
and temperature on agricultural productivity [32]. Rainfall is the main
production-limiting factor in the tropic region: a small variation in timing
and amount of rain can result in high changes in interannual crop yields. In
temperate regions, temperature is most essential in defining the length of the
growing season. The precipitation interacts in a very complex manner with
temperature to influence the crop growth. Any specific climate variation will
affect agriculture in the tropical and temperate regions in various ways [33].
Impact of climatic variation crop pathology
Wide number of studied have been made on how climate
affects plant diseases. It has been concerned with day-to-day weather
conditions rather than with year-to-year climatic variability [34]. A variation
in prevailing climatic conditions or a variation in climatic variability may
alter plant disease development by affecting: [35]
·
The speed of development
and number of pathogen or vector generations
·
the geographical
distribution of the host, pathogen, or vector, particularly on the margins of
their respective distributions
·
The dispersal of the
pathogen or vector with respect to synoptic-scale movement
·
The host-pathogen
interactions that have evolved into a functional system
·
The control of disease
Environmental changes can also affect host-pathogen
interactions by modifying their courses of development with respect to each
other. It is also possible that climatic variations could reduce a crop's
vulnerability by putting its development and that of the pathogen out of phase with
each other [36].
Food security and climate change:
a conceptual framework
Food
systems present in biosphere, along with all other changes of human activity.
Some of the significant manifestation in the biosphere that are expected be
from global warming will occur in the more distant future, as a consequence of
changes in average weather conditions [37]. The most likely scenarios of
climate changes indicate that increases in weather variability and incidence of
extreme weather events will be significant now and in the nearby future. The
projected increase in mean temperatures and precipitation will not manifest via
constant gradual changes, but will instead be experienced as increased
duration, frequency and intensity of hot spells and precipitation events [38].
Whereas the annual occurrence of hot days and maximum temperatures are expected
to increase in everywhere in the globe, the mean global increase in
precipitation is not expected to be uniformly spread around the world. In
general, it is expected that wet regions will become wetter and dry regions
more dryer. A conceptual framework on climate change and food security
interactions has been developed to highlight the variables defining the food
and climate systems for this analysis [39]. The climate change and food
security framework expose how climate change affects food security outcomes for
the four main components of food security in various direct and indirect ways.
These four main components of food security are [40].
- Food availability
- Food accessibility
- Food utilization
-
Food system stability
Climate change variables greatly influence the
biophysical factors, like plant and animal growth, biodiversity, water cycles
and nutrient cycling, and the ways in which these are managed through
agricultural practices and land use for production of food. However, climate
variables also have an effect on physical/human capital which indirectly
influence the economic and socio-political factors that govern food access and
utilization and can also threaten the stability of food systems [41]. All of
these impacts change themselves in the ways in which food system activities are
done. The framework proves how adaptive adjustments to food system activities
are needed all along the food chain to cope with the impacts of climate
manifestations. The climate change variables that are considered in the CCFS
framework are as follow; [42]
1. The
CO2 fertilization effects of higher amount greenhouse gas
concentrations in the atmosphere
2. Increased
rate of mean, maximum and minimum temperatures;
3. Gradual
manifestation in precipitation: increase in the frequency, duration and
intensity of droughts;
4. Manifestation
in the timing, intensity duration and geographic location of rain and snowfall
5. Increase
in the intensity and frequency of storms and floods
6. Greater
seasonal weather variability and changes in start and end of growing seasons
Evidence
indicates that the frequent and intense extreme weather events like droughts,
heavy storms, heat and cold waves and floods marking rise in sea levels and
increasing irregularities in seasonal rainfall patterns bring floods are
already having immediate effects on not only food production, but also
incidence of food emergencies, food distribution infrastructure, human health
and livelihood assets in both rural and urban areas [43]. In addition, less
immediate impacts are expected to be from gradual manifestation in mean
temperatures and rainfall. These manifestations affect the suitability of land
for various types of crops and pasture; the health and productivity of forests;
the incidence and vectors of different types of pests and diseases; the
distribution, productivity and community composition of marine resources; the
biodiversity and ecosystem functioning of natural habitats and the availability
of good-quality water for crop, livestock and inland fish production [44].
Arable land is likely to be lost owing to increased aridity and also associated
salinity, groundwater depletion and sea-level rise. Food systems will be
affected by internal and international migration, civil unrest triggered by
climate change and resource-based conflicts [45].