Teacher’s Notes
Will climate change affect how well food crops grow?
Introduction
This experiment aims to encourage students to think about some of the possible effects of
climate change on farming food crops in the future.
Predicted climate change scenarios for the next several decades are likely to have impacts on
farmers’ ability to produce food crops. The website
(http://www.defra.gov.uk/foodfarm/landmanage/climate/index.htm ) of the UK’s government
department responsible for agriculture, the Department for Environment, Food and Rural
Affairs (Defra), includes a series of predicted changes which will affect crop growing.
Defra’s list includes temperature changes, changes in seasonality, hydrological changes
(flooding and drought), changes in pest and weed levels, and increases in atmospheric carbon
dioxide (which affects plant photosynthesis).
Globally, these changes will affect different parts of the world in different ways, and some
places are likely to experience other changes too. For example, low lying coastal areas might
see incursions of sea water due to sea level rise caused by melting glaciers and ice caps. In
other areas, increased use of wells for irrigation might become contaminated by salty (saline)
water. The salt in such water is toxic to many crop plants.
These potential changes are uncertain, complex and frequently inter-related. It is difficult to
predict exactly which changes will affect particular places and at what time. However,
because of our need to grow crops to feed ourselves, and because of the planet’s growing
population, it is certainly worth exploring how some of the changes directly affect how easy
or difficult it is to grow plants that we eat as food.
Method
The aim of the experiment (which should take about a week to run) is to simulate the effects
of some environmental changes on plant growth, using cress (as this germinates and grows
quickly and easily).
Equipment needed: foil trays, kitchen roll, cress seed, water, salt, sand/gravel, heat lamp.
Each group of students is assigned an environmental change (see below). Each group then
prepares two foil trays for growing cress (most should have done this before!): it is important
that the same amount of kitchen roll is used in each tray and that the same number of cress
seeds is used in each tray (a kitchen measuring spoon can be used to achieve this – no need to
actually count the seeds!), so that the experiments are not biased by differences in set up.
The first tray is a control experiment. That is, the cress seeds should be placed on the
dampened kitchen roll, and left to grow. The kitchen roll can be re-dampened if necessary.
The second tray is the one subjected to an environmental change. One from the list below can
be assigned to each group.
i.
Higher temperature: place the tray under a heat lamp while the cress grows. The
kitchen roll will probably need to be kept damp as the heat will evaporate the
water. As an additional experiment, the group could try one tray with this extra
watering, and one without, to simulate heat and drought together.
ii.
Drought: give the seeds less water than the control, or none at all. The group could
try several trays with different levels of watering.
iii.
Flood: rather than the gentle addition of small amounts of water given to the other
trays, once the seeds have germinated pour water on rapidly so they are covered.
Flood water tends not to be clean but to carry sediment, so as an additional
experiment the group could try flooding the cress and then partly burying it under
sand or small sized gravel.
iv.
Salty water: the tray should be watered with saline water. Sea water salinity on
average is 35 parts per thousand, i.e. 3.5g/l. Very roughly, this can be
approximated by mixing ½ to 1 teaspoon of salt into a mug of hot water. Different
experiments could use saline water from the start, or start with fresh water for
dampening the kitchen roll and then switch to saline water thereafter.
The ‘ control’ cress seeds should germinate after a day or two and keep growing for a week or
more. The object then is to compare growth of the cress in the control with growth in the
altered environment, as well as to compare the different altered environments. The students
can be encouraged to think about how to measure growth: for example they could measure the
height of the ‘crop’, or ‘harvest’ the crop after a set period and either weigh it if precise scales
are available or think about other ways of estimating the volume or weight of the harvest.
They can then draw up a table or chart to record findings and help them to analyse the results.
Did the experiments make the group successful ‘farmers’? Or would there be a cress famine
under their changed environmental conditions?
Further discussion
Following the experiment, here are some suggestions for further discussion.

Farmers: How might farmers respond to some of the problems caused by climate
change?
i.
In drought conditions, they might irrigate. But as mentioned above this might lead
to ‘salinisation’ of the soil.
ii.
If they are faced by regular flood conditions, flood defences can be constructed.
But, these are expensive, and may divert the problem elsewhere.
iii.
Science suggests it can provide answers to some environmental changes. Genetic
modification (GM) of crop plants so they are more tolerant of drought or salinity is
possible. But GM is very controversial for a number of reasons.
iv.
More sustainable , ‘agro-ecological’ techniques might be adopted, such as
cultivation techniques which harvest and preserve water in the soil to help offset
drought conditions.

Geography: where will food be grown in the future?
Particular parts of the world are predicted to suffer more ‘climate stress’ than other
parts. For example, Mediterranean areas and Sub-Saharan Africa, already dry, are
likely to suffer more extreme drought. Other more Northern areas might actually
be able to grow more food as they become warmer.
ii.
Climate change scientists predict geographical changes in what crops are grown
where, with a general northward migration of crop types (in the northern
hemisphere).
i.

How will people cope? How might the effects of climate change on crop production
affect the price of food, and what might be the social consequences?
For example, reduced food production is likely to increase the price of food. Poorer people,
and particularly poorer people in Developing countries, will find it harder to grow or buy
enough food. Some people have argued that this is likely to lead to mass migration as people
move in search of food or useable farmland, and that this might lead to future conflict.
Governments and scientists are increasingly thinking about how to ensure sustainable food
production and ‘food security’ in a world of changing environmental conditions.

Experiments: were there any problems with the experiment? Did it work – did cress
growth vary with the environmental changes imposed? Did the results match or differ from
prediction? Were the results valid for explaining what might happen in the real world?
i.
Clearly, cress isn’t a major food crop and it was only grown for a week not a
whole season. How could experiments be conducted with more important crops,
like wheat or rice?
ii.
In reality, climate change will be much more changeable than in the experiments,
and with mixed impacts. Is it possible to monitor what is going on in the real
world to get a better understanding of environmental change?
iii.
Were there any problems with running the experiment – did any farmers forget to
water their crops !
iv. What are the best ways to measure and record results, and what are the best ways to
analyse differences between different trays of cress?
Will climate change affect how well food crops grow?
Most climate scientists agree that our climate is changing as a result of human activity over
the past couple of centuries. This is mainly due to burning fossil fuels like oil, coal or gas.
Climate change is likely to make the world warmer overall, and will also affect the amount of
rainfall we get. Across the planet, different places will be affected in different ways. Some
places may get warmer and wetter. Other places may get warmer and drier. On a warmer
planet Earth, much of the ice stored at the North and South Poles, and in glaciers, is likely to
melt. All of that extra water goes into the sea, and a bit like a bath filling up, sea levels will
get higher. Lowland areas next to the sea may become flooded.
We all rely on farming to grow the food that we eat. Climate change is likely to affect how
well crops grow. Do they grow better when it is warm? What happens to crops when they get
too dry, or if they are flooded? What happens to plants if rising sea levels makes the soil they
grow in salty? This experiment aims to test the effects of different environmental changes on
crops of cress plants.
For this experiment, you will need:
 Foil trays
 Cress seed
 Kitchen roll
 Water
Method
1. prepare two foil trays for growing cress: fold two sheets of kitchen roll so that they fit
into the tray. Sprinkle cress seeds over the kitchen roll, use the same number of seeds in
each tray. The seeds should germinate within a couple of days, and grow for a week or
more.
2. label one tray your ‘control’ experiment. Water the seeds and leave them to grow. If the
kitchen roll gets dry, gently add some more water.
3. in the second tray, create a changed environment by simulating one aspect of climate
change. For example:
 make it warmer: use a lamp shining on the seeds.
 make a drought: use a lot less water than you do for your first tray, or no water at all.
 make a flood: once the seeds have germinated pour water into the tray quickly to cover
the plants. You could also use sand or gravel to act as the sediment which floods
usually wash onto the land.
 make it salty: use salty water to water the plants instead of fresh water.
After growing your cress experiments, compare the ‘control’ experiment with the cress grown
in the changed environment.
What is the best way to measure and compare how well the cress has grown in the different
conditions?
What is the best way to record the results of your experiments? For example, could you draw
up a table comparing different results? Or could you make a graph to show the differences?
How did the cress plants respond to the different environmental conditions they were grown
in? Did you expect these results?