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12 October 2020 | Story Leonie Bolleurs | Photo Supplied
Adriaan van der Walt
Although several international studies have used temperature metrics to statistically classify their seasonal divisions, a study in which Adriaan van der Walt was involved, would be the first known publication in a South African context using temperature as classification metric.

Gone are the days when we as South Africans would experience a three-month spring season, easing into summer, and then cooling off for three months before we hit winter.

Adriaan van der Walt, Lecturer in the Department of Geography at the University of the Free State (UFS), focuses his research on biometeorology (a specialist discipline exploring the role and climate change in physical and human environments) as well as climatology and geographic information systems.

He recently published an article: ‘Statistical classification of South African seasonal divisions on the basis of daily temperature data’ in the South African Journal of Science.

In this study, which Van der Walt undertook with Jennifer Fitchett, a colleague from the University of the Witwatersrand, data on daily maximum and minimum temperatures was collected from 35 meteorological stations of the South African Weather Service, covering the period between 1980 and 2015.

They went to great lengths to ensure that they had a complete set of data before presenting it to demonstrate seasonal brackets.

First for South Africa

Their statistical seasonal brackets indicate that South Africans now experience longer summers (from October to March), autumn in April and May, winter from June to August, and spring in September.

Although considerable work has been done using rainfall to determine seasonality in Southern Africa, Van der Walt believes that these methods did not work well as there are too many inconsistencies in this approach, as identified by Roffe et al. (2019, South African Geographical Journal). To make matters more complicated – as a semi-arid region, and with desert conditions along the west coast – some regions do not have enough rainfall to use as a classifier.

Temperature, on the other hand, worked well in this study. “Temperature, by contrast, is a continuous variable, and in Southern Africa has sufficient seasonal variation to allow for successful classification,” says Van der Walt.

He continues: “Although several international studies used temperature metrics to statistically classify their seasonal divisions, this study would be the first known publication in a South African context using temperature as classification metric.”

Van der Walt says what we understand as seasons largely relates to phenology – the appearance of blossoms in spring, the colouration and fall of leaves in autumn, and the migration of birds as a few examples. “These phenological shifts are more sensitive to temperature than other climatic variables.”

Seasonal brackets

According to Van der Walt, they believe that a clearly defined and communicated method should be used in defining seasons, rather than just assigning months to seasons.

“One of the most important arguments of our work is that one needs to critically consider breaks in seasons, rather than arbitrarily placing months into seasons, and so we welcome any alternate approaches,” he says.

A number of sectors apply the temperature-based division to their benefit. “For example, in the tourism sector it is becoming increasingly important to align advertising with the season most climatically suitable for tourism,” says Van der Walt.

Temperature-based division is also used to develop adaptive strategies to monitor seasonal changes in temperature under climate change. However, Van der Walt points out that each sector will have its own way of defining seasons. “Seasonal boundaries should nevertheless be clearly communicated with the logic behind them,” he says.

News Archive

A mind shift needed in agriculture in Africa
2010-12-02

Prof. Frans Swanepoel (Centre for Sustainable Agriculture and Rural Development), Prof. Monty Jones, Prof. Driekie Hay (Vice-Rector: Teaching and Learning), Prof. Alice Pell (Cornell University, USA), and Prof. Izak Groenewald (Director of the Centre for Sustainable Agriculture and Rural Development) at the inaugural lecture of Prof. Jones as Professor Extraordinary. 
- Photo: Stephen Collett

Food stability is essential for stability in all countries around the world. Radical interventions, and not incremental changes, are necessary to end hunger and poverty in Africa, said Prof. Monty Jones, Professor Extraordinary in the Centre for Sustainable Agriculture and Rural Development at the University of the Free State (UFS), in his inaugural lecture.

Prof. Jones is Executive Director of the Forum for Agricultural Research in Africa (FARA) and Chairperson of the Global Forum on Agricultural Research (GFAR). In his lecture he focused on the contribution of agricultural research to development and food security in Sub- Saharan Africa.

He said Africa is not known for good politics to promote food production. Countries under invest in research, education, knowledge management, agriculture finance, etc. There is also uncertain and restricted access to land. He specially mentioned women’s access.

Sub- Sahara Africa moved from being a net exporter of food to a net importer of food (28%). “Government spending on agriculture and transport went down and stagnated. A mind shift is necessary. Africa has the resources. We must take advantage of the opportunities,” he said, and added: “Africa must create visionary and inspirational leaders and managers who can drive developmental issues.”

Prof. Jones emphasised that fact that nutritional security is just as important as food security. The number of hungry people has grown to more than a billion in 2009. Hunger is the most severe in the developing world, especially Africa. Added to this is Africa’s population growth that i s also higher than the rest of the world. It is estimated that the demand for food in Africa will double in the next 40 years.

“Research and development alone cannot win the war against hunger in Africa. Everyone has a role to play,” he said.
– Leatitia Pienaar.

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