A number of infectious plant diseases result from viruses. Major crops that are seriously affected by virus diseases include: tobacco, potato, sugar beet and cane, peach, orange, cotton and wheat. Most of the plant viruses impair or destroy chlorophyll, causing the plant to wilt or die; some viruses, though, stunt or otherwise deform plants without seriously affecting the chlorophyll.

Racism and racial discrimination are in practice used in a range of overlapping ways. The ambiguity of their use often causes political and even scientific discourse to become confused and itself prevents progress towards constructive solutions. Racial discrimination can be considered as the broader concept following its definition in the international Convention on the Elimination of All Forms of Racial Discrimination as any distinction, exclusion, restriction or preference based on race, colour, descent, or national or ethnic origin which has the purpose or effect of nullifying or impairing the recognition, enjoyment or exercise, on an equal footing, of human rights and fundamental freedoms in political, economic, social, cultural or any other fields of public life. Such discrimination may be based upon ideas or theories of superiority of one race or group of persons of one colour or ethnic origin, which may be used to justify or promote racial hatred and discrimination in a wide variety of forms. Such action may encourage acts of violence or incitement to such acts against groups of persons of another colour or ethnic origin.

Racism has been the subject of several declarations by UNESCO. In 1978 it was defined as including racist ideologies, prejudiced attitudes, discriminatory behaviour, and institutionalized practices, resulting in racial inequality, as well as the fallacious notion that discriminatory relations between groups are morally and scientifically justifiable. Racism as a doctrine attributes the determination of human capacities to specific inherited physical traits that are considered to distinguish a race. Prejudice and discrimination on the ground of race, colour or ethnic origin occur in a number of societies, where physical appearance – notably skin colour – and ethnic origin are accorded prime importance. "Racism" has increasingly come to mean the hostility that one person feels for another because of his or her colour alone. These racist beliefs have been so widespread that although authoritatively and consistently proved to be erroneous, they still continue to be an important cause of prejudice.

Racism, which takes a number of forms, is a complex phenomenon involving a whole range of economic, political, historical, cultural, social and psychological factors. It is generally a tool used by certain groups to reinforce their political and economic power, the most serious cases being those involving apartheid and genocide. Racism exists in all parts of the world. Violence, even genocide against indigenous groups, has become endemic in many countries. Racism is often aggravated by international systems backed by powerful economic and military factors. Land rights claims of indigenous peoples are often rejected in the name of development and national security. Immigration policies and practices discriminate on the basis of race in many parts of Europe, Asia and North America. Education policies deny equality of opportunity and employment on the ground of race.

Although maintaining the conception of a socially unified society, racial divisions may be preserved but expressed in other terms, so that in reality there is racial differentiation. Some characteristics of society favour a racial differential, incorporated in polity, and expressed as cultural barriers, de-facto segregation, inequality and demographic recognition of racial and ethnic categories. Conflict may be acknowledged but the significance of racial and ethnic difference for the conflict may be denied.

Malaria is a parasite of red blood cells and the world's number one infectious disease. It is caused by infection of the liver with parasites of the genus Plasmodium, transmitted by the bite of infected anopheline mosquitoes Anopheles bifurcatus. The parasites cause the rupture of red blood cells and, in its worse cases, life-threatening anaemia, coma or death. The disease is characterized clinically by recurrent paroxysms of chills, high fever, seizures, sweating and prostration. It can lead to anaemia, kidney failure or rupture of the spleen. In man, malaria is produced by four specific parasites: Plasmodium vivax, P. malariae, P. ovale and P. falciparum. Falciparum malaria is the most life-threatening and has a fatality rate in untreated cases of 25%; it is transmitted by its African mosquito vector Anopheles gambiae.

Malaria is worsening in many parts of the world. It is a major threat to health and development, is primarily an environmental and socio-economic problem. Past reliance on narrow strategies is increasingly seen as the reason for the resurgence of this debilitating disease. The P. falciparum] parasite has continued to evolve resistance to almost all drugs in use (chloroquine, sulfadoxine/pyramethamine, and mefloquine). In areas of mosquito control, research with bed nets impregnated with pyrethroid insecticide offers hope of at least partial control of transmission of the disease in certain epidemiological situations. However, many people cannot afford the mosquito nets, which cost $5-10. Patients can usually be saved if they receive prompt medical treatment, but many of them cannot afford doctor's fees or the cost of travel, in total often less than $20.

Increasing population density, urbanization, industrialization and other development schemes, are exerting ever increasing pressure on the carrying capacity of land and resources, leading in particular to a rapid rate of deforestation, expanding desertification in some countries, and the near extinction of some wildlife species. Physical factors such as earthquakes, hurricanes, monsoon rains and the immense problem of poverty in some countries accelerate the decline in environmental resources.

Trade protectionism is the result of governments acting to save certain sectors of their economies from foreign competition. The impact of this on the fledgling industries is considerable but they are in no position to retaliate. Protectionist policies have also been directed by developed countries against each other, but this is usually carefully negotiated to avoid retaliation.