Propagule pressure rather than population growth determines colonisation ability: a case study using two phytophagous mite species differing in their invasive potential

Water shortage in South Africa is a mixture of many factors: limited and highly polluted watercourses, low rainfall, fast growing population and high evaporation rates. Many studies on watercourses have shown a decline on quality due to the ongoing pollution caused by urbanization, mining, industry, power generation, afforestation and agriculture. Given the current forecasts based on population growth versus the country’s limited water resources, it is unlikely to keep existing patterns regarding the use of water and the discharge of wastes. Predictions are also indicating that pollutants will continue to accumulate in freshwater resources independently of the population growth in South Africa. Issues associated with water quality can turn out to be worsened with environmental devastating consequences. For instance, in the agricultural sector it may lead to a drop in yields and quality for fruits and crops followed by soil contamination. It can harmfully affect the population and aquatic health. Furthermore, water quality deterioration can affect the costs related to purification processes resulting in an increased price of clean water. Human induced activities causing salinization, eutrophication, acidification, presence of pathogens in watercourses, inappropriate waste discharge practices and sewage spills are major causes influencing or deteriorating water quality in South Africa.

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Population Growth and Urban Systems Development: A Case Study

Economic Geography ◽

10.2307/143626 ◽

1982 ◽

Vol 58 (1) ◽

pp. 87

Author(s):

Clare Stapleton ◽

G. A. Van der Knaap

Keyword(s):

Population Growth ◽

Systems Development ◽

Urban Systems

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Nuptiality to regulate the commons? The case of the Don Cossacks (South Russia), 1867–1916

Oxford Economic Papers ◽

10.1093/oep/gpz077 ◽

2020 ◽

Author(s):

Noël Bonneuil ◽

Elena Fursa

Keyword(s):

Population Growth ◽

Net Present Value ◽

Early Marriage ◽

Age At Marriage ◽

Agrarian Economy ◽

Traditional Societies ◽

The Commons ◽

Age Of Marriage ◽

Important Marker

Abstract Sustainability in the commons has been associated with the optimal net present value controlled by the harvest rate under stationary population. Population growth however disrupts this scheme. In traditional societies, fertility was regulated by age at marriage. In times of population growth and limited resources, economic sustainability then requires that age of marriage should be raised. In the case study of the Don Cossacks, 1867–1916, early marriage, which was an important marker of social cohesion, was too slow to increase when mortality declined, fuelling a population growth that threatened the agrarian economy: age at marriage then appears to be essential to the theory of the commons in traditional societies.

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