Download CODE: PPI-KLIM - Plant Dynamics

[CODE: PPI-KLIM]
[Prophyta Annual, May 2000]
>rkp THE FUTURE STARTS NOW
>bkp GLOBAL CLIMATE CHANGE
>kop Breeders should look for new varieties
>itr A global temperature rise of 1 to 3.5 degrees Celsius by the year 2100, 3-10
percent more precipitation and a sea level that is 15-95 cm higher than today,
does not sound like dramatic changes. But even if there will not be a sudden
change like the turning of the warm Gulf-Stream, it shall have serious effects.
Agricultural zones, for instance, could shift towards the poles by 150-550 km in
the mid-latitude regions.
>aut Monique Krinkels
>txt Plants can easily keep pace with changes that occur over an extended
period of time. Natural selection processes make sure that plants adapt to their
environment. A mere 1-3.5ºC rise in the course of a century therefore seems to
be nothing to worry about. But according to the Intergovernmental Panel on
Climate Change (IPCC) this change is larger than any climate change
experienced over the last 10,000 years.
Moreover, it is not the rise in itself that disquiets researchers most. “It is the
expected incidence with which extremes will occur that causes serious
concerns”, states Dr. Ad Schapendonk of Plant Research International at
Wageningen, the Netherlands. His research is devoted to photosynthesis and
stress physiology of plants. Together with his colleague Dr. Oene Dolstra, who
is specialised in the genetic analysis of variation in physiological traits , he
explains the changing climate and the measures breeders should take.
>tkp Human interference
Since five years meteorologists are convinced that the observed climate change
is not due to a natural process, but caused by human activities. Greenhouse
gases as carbon dioxide, methane and nitrous oxide are released into the
atmosphere. Industrial processes add artificial chemicals called halocarbons and
long-lived gases such as sulphur hexafluoride to this. Automobile exhaust
fumes are increasing the amount of ozone in the lower atmosphere. These gases
increase the atmosphere’s ability to absorb infra-red radiation.
Human emissions will force the climate to restore the balance in energy flows.
This adjustment will include a global warming of the earth’s surface and lower
atmosphere. Even a small rise in temperature will be accompanied by many
other changes, for example in cloud cover and wind patterns. Some of these
changes may act to enhance the warming, others to counteract it.
There are many uncertainties about the scale and impacts of climate change,
particularly at the regional level. Because of the buffering effect of the oceans,
surface temperatures do not respond immediately to greenhouse gas emissions.
But in general it can be said that the faster the climate changes, the greater will
be the risk of damage. Furthermore, regions with a delicate balance might suffer
most. Rain forests like the Amazon might be ruined if the fragile equilibrium
between evaporation and precipitation is even slightly disturbed.
“But models to predict future changes are not easy to interpret”, warns Ad
Schapendonk beforehand. “A few years ago a model has been built to describe
competition between plants. Literally no-one was able to foresee that
PIJPESTROOTJE would win over heather, as it occurred in The Netherlands.
It just underlines the prudence with which models should be applied.”
>tkp Africa
If it were only higher temperatures and an increased amount of CO2 many plant
species could cope easily by growing more vigorously. Torrential rains
alternated with draughts, flooding, combined with more hail- and thunderstorms
will offer more severe problems. Unfortunately, the changing climate will have
devastating effects upon regions which have to cope already with a marginal
agriculture. The poor and disadvantaged are the most vulnerable to the negative
consequences. The three-year draught in Eastern Africa, threatening 16 million
people with starvation, is supposedly a result of climate change.
“There is no way, however, breeding could have prevented their misery. Even
the strongest grass varieties need water once in a while. The only way to avert a
calamity of this nature is to depopulate the area. The situation will only worsen,
as it is expected that these extremes will occur more often”.
At the same time, Oene Dolstra ? underlines the importance of breeding for
Africa. “A continuous flow of new varieties, strong local breeding efforts
including participatory breeding may safeguard the continent against current
and future disasters. Sorghum, beans and maize will become even more
important crops in Africa”, he predicts. “These crops are suitable to a warm and
dry climate. Breeders should however search fornew varieties, to better adapt
the plant to drought and other stresses related to global warming”
>tkp Studies
During the last 20 years the influence of warmth, light, moisture and CO2 on the
growth of plants have been thoroughly studied. It has been discovered among
others that plants can adapt to periods of drought, depending on the period by
growing slower at the start of the season or slowing down the ripening of the
seeds at the end of it. Besides, the shape of its root-system can help it to survive
a period of drought. He also promotes the breeding of C4-type plants. C4 is a
type of photosynthesis with which a plant can bindcarbon dioxide more efficient
and as a consequence needs less water.
“Further, marker technology can be applied for a quick selection of the desired
phenotypes”, adds Oene Dolstra of Plant Research International. A study
supported by CIMMYT has revealed genes that increases the tolerance to
droughts and salinity. These genes can be transferred into new varieties by
traditional and molecular-marker-aided breeding methods.
The situation in Asia is less dramatic than in Africa. “These countries have a
better infrastructure. The international rice research institute IRRI has an
impressive track-record in the development of new varieties”, says Dr.
Schapendonk That does not mean the continent will not notice any differences.
The land use will be drastically effected as many regions will become
unsuitable for agriculture. This is the result of the salting up of fields due to the
sub-optimal use of water and irrigation systems.
Besides, increase in yield does not keep up with population growth. That means
that breeders have to seek for varieties with stress tolerance and an improved
use of nutrients.
>tkp Lucky Europe
For Europeans the forecasts are not alarming at present. Grasses will be able to
compensate the water shortage in periods of drought by the raised CO2 as that
improves its efficiency. The expected increase in temperature willenable a more
economicand probably even large-scale cultivation of maize for grain in NorthWest Europe. . The cultivation of sunflowers will also move up North.
But the raised temperatures will also have disadvantages. Grains will have to be
grown more in the North, because the increased temperature in temperate zones
will shorten the period of grain filling and consequently decrease yield. That
means that breeders should look for adjusted daylight characteristics to adapt
the crops for Scandinavian countries. In the Mediterranean countries farmers
should pay more attention to erosion and irrigation, as rainfall will be restricted
to shorter periods.
“But the current models are not sufficiently elaborate to accurately predict the
weather in certain regions”, says Ad Schapendonk. “Many side effects are still
under investigation. For instance, if the temperature rises, regions with
permafrost will thaw. As this has a large amount of methane, this gas will be
released into the atmosphere. Methane is a far stronger greenhouse gas than
CO2, giving temperature rises an extra impulse.”
>tkp Breeder’s tasks
One of the consequences breeders will have to face is that insects and other
pathogenes will adapt quickly to the new circumstances. As the life-span of
some of these pests is shorter than that of plants the chances are that they will
adapt even faster to the changing climate. It is one more reason to emphasise the
importance of disease resistance.
Further the positive effect of a higher photosynthesis should be strengthened.
“Today a potato responds only during four weeks to a higher level of carbon
dioxide with a higher photosynthesis. It is a complex mechanism, but breeders
should attempt to prolong that period.”
Due to the higher temperatures the ageing of young leaves will be accelerated.
This should be counteracted because the young leaves intercept most of the
incoming light. This reduces the efficiency of the photosynthesis process.
Breeding cannot solve all of the problems climate change is causing. “Farmers
should grow the crops that are best suited to the climate region. But that
requires free trade, without any restriction between all countries and that
remains a political issue. Growing rice in Pakistan and China is often less
efficient as growing this staple crop in India.
The salting up of the rice paddies due to the use of irrigation in Pakistan and
the decrease of the water table in China are causes for alarm. If that does not
change, the soil will be barren in a few years time. But the current political
situation will not allow Pakistan to become fully dependent on its neighbouring
country for rice. In future the choices of the politicians will be restricted
because the availability of arable land does not keep pace with regional
developments in the growth of the population and thus they have to adjust their
scope on the world”, states Ad Schapendonk.