ZIMBABWE'S agro-ecological zones (AEZs or natural regions) have shifted drastically because of the devastating effects of climate change and global warming. Although the changes have not been officially adopted, major shifts have occurred in the drier Regions 4 and 5, which are prone to drought, and will now almost certainly drift wider into hunger.
Latest research by Mr Raymond Mugandani et al shows that the original five natural regions have not decreased nor increased in number though significant changes have been experienced in their size, structure and composition.
According to the research, Region 1, which is the prime agriculture land concentrated largely as a strip in eastern Zimbabwe, has expanded by 106 percent while Region 2 has declined 49 percent. Region 3 shrunk 14 percent whereas the predominantly drier Regions 4 and 5 have expanded by a dreadful 5,6 percent and 22,6 percent respectively.
Annual rainfall distribution for Regions 4 and 5 is expected to be below 600mm while Region 1 will record upwards of 1 000mm. The other regions will range between 550mm and 1 000mm. Now, this alters the face of agriculture and how it is practised in a significant way, particularly for an economy overly reliant on land for achieving food security, employment and earning foreign currency.
"The shrinking of Natural Regions 2 and 3, which are the main food producing areas in Zimbabwe point to a possible reduction in food production and thus problems of food insecurity," said Mr Mugandani of the Midlands State University's Water and Land Resources Department in the study.
"The shifting of the natural regions' boundaries observed, strongly points to evidence of climate variability and change."
The effects of climate change are evident in Zimbabwe with increasing variability in rainfall patterns, higher average temperatures, as well as increased frequency and extremity of droughts and floods.
Agriculture is the hardest hit. Food production has fallen sharply. This year alone, the country was forced to import over 50 percent of its maize requirements, the staple crop.
Over the past century, Zimbabwe has experienced a warming of 0,7 degrees Celsius, and estimates are that it will worsen. The research indicated that the new regions must be tried "and see how they fare".
Another study by Daniel Nyamangara on the north-east of Zimbabwe a few years ago depicted major changes in rainfall and temperature patterns. It showed that the percentage of total areas receiving rainfall below 790mm annually was increasing with time while those receiving above 910mm were decreasing.
Mean average maximum and minimum temperatures were increasing at a yearly rate of 0,031 degrees Celsius and 0,013 degrees Celsius respectively.
"The area was becoming drier and hotter. The increasing frequency of low rainfall and high temperatures could indicate advancing desertification," Nyamangara said in the study.
Other agro-ecological zones studies by Kainamura (2000) and another by Chikodzi (2009) for Masvingo province established that boundaries for the AEZs had and were shifting, as a result of continuous changes in the climate system.
Met Dept starts work to "officialise" new AEZs
The Meteorological Services Department of Zimbabwe believes the natural regions boundaries may have indeed shifted due to factors such as climate change and changes in land use. To this end, MSD acting deputy director operations Mr Terrence Mushore said last week that work had begun to retire the zones and come up with a new map, which showed the updated picture.
He said this was important, as the results will assist in crop and livestock selection in different areas of the country. The successful completion of mapping the new zones "will be expected to improve agricultural productivity and enhance the effectiveness of the land reform programme".
It would also "assist in sustainable development and in the formulation of the national policies on agriculture and water, as well as in water resource monitoring and management."
However, the project required a multi-disciplinary approach as data and expertise required was from different fields such as climate, agriculture, geographical information systems, agro-meteorology and surveying.
The project, likely to take 18 months, will include the ministries of Lands; Local Government; Water Development and Management; Agriculture; and the Ministry of Transport, Communications and Infrastructure Development, Zinwa, seed companies, universities and NGOs. Mr Mushore explained that selection of agriculture activities to practise is determined by a combination of factors which include land use, soil type, slope, altitude, rainfall and temperature.
"Each agricultural activity has its own favourable combination of conditions under which productivity will be at its peak and extremes where yield will be significantly reduced. This implies that there are places whose combination of conditions under which they exist is not conducive for certain crops or for livestock production such that if these activities are forced without modifying the conditions yield will be minimal or non-existent."
How important are agro-ecological zones?
David Chikodzi, climate specialist and lecturer at the Great Zimbabwe University, says agro-ecological regions show how land with different potentials and constraints is distributed within a country, provinces and districts.
He said such information would then support the development of land use policies and enabling strategies in areas such as the provision of appropriate, area-specific, extension information and advice.
"Agro-ecological zones are standard tools for prioritising agricultural research, agro-technology transfer and investment because they offer relevant, available information about target environments," Chikodzi said in his research paper exploring natural region changes in Masvingo province.
"Investment in agriculture needs to be increasingly directed at agro-ecological zones where output benefits may be expected to be greatest. This first requires that the zones themselves be well defined."
The zones are important also for long-term frost protection measures. Agro-ecological zones may be defined as land areas characterised by similar climates, agricultural activities and ecology.
Zimbabwe has five AEZs originally defined in the 1960s by Vincent and Thomas. Experts believe this study erred in many key areas, which include its failure to consider effective rainfall and the use of very few data points and less developed tools.
Mr Mugandani said the need to revisit the original regions had been precipitated by, among other things, the need to correct the limitations already noted, as well as to factor in the changes in the local climate system. The Mugandani study reclassified the natural regions using soil data, mean annual rainfall and length of growing season. Rainfall data from selected meteorological stations covered the period 1972-2006.