CLIMATE VARIABILITY, AGRICULTURE AND REMOTE SENSING - Food Security, Food Prices and Climate Variability - page 60

Trends in agriculturally relevant growing season parameters
In order to look at the joint effect of temperature and precipitation on growing conditions,
many researchers have looked at changes in vegetation phenology. Phenology is the study of
periodic biological phenomenon such as emergence, flowering, maturation and senescence of
vegetation. Calculating trends in growing season parameters, including the start of the season,
length of the growing period and the position of the height or peak of the season, in the
primary regions with rainfed agriculture during the past 26 years provides an understanding
of how temperature and precipitation have changed during the period. By using satellite data
of vegetation dynamics, we can determine if it was moisture or temperature conditions that
are most related to agricultural production variations, as this question is a central one for pro-
jecting the impact of climate change on food production (Lobell et al ., 2008) and identify
where the start of season, peak timing and length of growing season have changed.
Estimates of changes in agriculturally relevant start, end and peak of the growing season are
based on extensive previous research using vegetation index observations as the basis for
measurements of phenological metrics (de Beurs and Henebry, 2010). Many other researchers
have worked to integrate remote sensing observations into agriculture applications, including
modeling variations in biomass and crop yield, monitoring vegetative stress and drought pro-
gression, assessment of phenological phase of crop development, crop acreage and cropland
mapping, and disturbances and land use change through time (Atzberger, 2013). These uses
of remote sensing data are well established and contribute significantly to our knowledge of
agriculture around the world.
Local agricultural production is a key element of food security in many agricultural coun-
tries in Africa. Climate change and variability is likely to adversely affect these countries, par-
ticularly as they affect the ability of smallholder farmers to raise enough food to feed themselves.
Seasonality influences farmers' decisions about when to cultivate, sow and harvest, and ulti-
mately the success or failure of their crops. Jennings and Magrath (2009) described farmer
reports from East Asia, South Asia, Southern Africa, East Africa and Latin America. Farmers
indicate significant changes in the timing of rainy seasons and the pattern of rains within
seasons, including:
• moreerraticrainfall,comingatunexpectedtimesinandoutofseason;
• extremestormsandunusuallyintenserainfallarepunctuatedbylongerdryspellswithin
the rainy season;
• increasinguncertaintyastothestartofrainyseasonsinmanyareas;and
• shortortransitionalsecondrainyseasonsarebecomingstrongerthannormaloraredisap-
pearing altogether.
The impact of these changes on farmers with small plots and few resources is large. Farming is
becoming even more risky because of heat stress, lack of water, pests and diseases that interact
with ongoing pressures on natural resources. Lack of predictability in the start and length of the
growing season affects the ability of farmers to invest in appropriate fertilizer levels or improved,
high yielding varieties. These changes occur at the same time as the demand for food is rising
and is projected to continue to rise for the next 50 years (IAASTD, 2008).
These farmer perceptions of change are striking in that they are geographically widespread
and are remarkably consistent across diverse regions ( Jennings and Magrath, 2009), but are