Frequently Asked Question

What are the adverse effects of increased UV-B radiation on crops and forests?

The UV-B radiation present in sunlight causes a wide range of responses in crops and forests but most plants have natural mechanisms that provide some UV shielding, but do not always have sufficient amounts for complete protection. Some types of crops and wild plants may suffer detrimental effects from increased UV-B radiation.

Only a small proportion of the UV-B radiation striking a leaf penetrates into the inner tissues. When exposed to enhanced UV-B radiation, many species of plants can increase the UV-absorbing compounds in their outer leaf tissues. Other adaptations include increased thickness of leaves, thereby reducing the proportion of inner tissues exposed to UV-B radiation and changes in the protecting waxy layer of the leaves. Several repair mechanisms exist in plants, including repair systems for damage to DNA and other vital biomolecules. The net UV damage a plant experiences is the result of the balance between the damage, protection and repair processes.

Some varieties of crops are UV-B-sensitive and produce reduced yield following an increase in UV-B. There are also UV-B tolerant varieties, providing us with the opportunity to breed and genetically engineer for UV-B tolerant crops. Commercial forests, tree breeding and genetic engineering may be used to improve UV-B tolerant plants. While many forest tree species appear to be UV-B tolerant, there is some evidence that detrimental UV-B effects accumulate slowly from year to year in certain species.

The biochemistry and physiology of plants are influenced by UV-B exposure, such as in the accumulation of UV-B absorbing compounds. It is not possible to conclude yet whether changes in UV-B irradiation will have any appreciable impact on the quality of food. Changes in plant biochemistry induced by UV-B radiation have been shown to influence the interactions between crop plants and
herbivorous insects.

During their evolution, plants and animals have adapted to particular environments. They have acquired protection and repair mechanisms appropriate for their particular
situations. However, the present rate of global change is so rapid that evolution may not keep up with it, particularly in long-lived plants like trees. Plants adapt to a rather specific UV-B environment, and a change in UV-B may be detrimental even though it is smaller than the difference between the natural irradiation at the equator and higher atitudes. For example, herbaceous plants
native to the southern tip of South America and the Antarctic Peninsula have been shown to be affected by the current high levels of ambient UV-B irradiation. Over a long time and many generations, there is the possibility that genetic adaptation can develop.

Multilevel effects of solar UV -B on plants and forests.