The Growth of Harare Metropolitan Area
A closer look at Harare Metropolitan Area's Land Use and Land Cover Change between 2015 and 2023
Zimbabwe is a landlocked African country, located in the southern part of Africa. Its capital city, Harare, previously known as Salisbury, lies in the north-east of Zimbabwe tucked at the watershed plateau of two major rivers; Zambezi on the north and Limpopo on the south. The city has been growing at a slow and steady pace for the past 2 decades which has been great in terms of development, however not all of its growth has been sustainable.
While the Harare Metropolitan Area has been hailed as the hub for the country's many economic, educational, and cultural activities, in recent years it has also gained an unfavorable reputation as one of the worst livable cities in Africa.
This unfavorable reputation has been credited to some of the city's unregulated construction practices, poor infrastructure, lack of adequate healthcare systems, and unsustainable land practices.
The city of Harare has grown from 616,000 in population in 1980 to more than 2.1 mil people in 2023.
A glance at these numbers paints a vague picture of what ground realities might be like but a closer look is needed to understand how the growth of Harare has transpired and how land use practices and land cover has changed over the years.
To explore this, change detection analysis was conducted and Land Consumption Rates of Harare Metropolitan Area was calculated.
Objectives
- To identify and quantify the trend, nature, and rate of land use and land cover dynamics from (2015 to 2023).
- To determine the land consumption rate trends for the city within the study period
Land Consumption Rate
Is a measure of the urban compactness. It indicates progressive spatial expansion of the urban built-up areas (the urban sprawl)
L.C.R = A/P
Where:-
A = extent of the city under a given land use/land cover in hectares.
P = Population of the city at a particular date.
For this study, the Change Detection and Land Consumption Rate was derived using the best practices outlined in the Good Practice Guidance 2021 from the United Nations Convention to Combat Desertification (UNCCD).
Note: While this use case falls primarily in SDG 11 - Sustainable Cities and Communities, the link to the Good Practice Guidance from UN-Habitat was not working. Hence, the guidance (schema, method, best practices) from UNCCD was used.
Datasets
For satellite imagery, datasets from Google Earth Engines Data Catalog for Sentinel Level-2A Harmonized were utilized. Two sets of satellite imagery were downloaded, one for 2015 and one for 2023. For consistency, the period between October to December was prioritized as dataset availability for Sentinel 2 starts from mid-June 2015.
Zimbabwe's national and regional boundaries on the other hand were sourced from the Geoboundaries website.
Methodology
Various tools from ArcGIS Pro's toolbox were used. The most important feature used for this use case was the Classification Wizard.
Land Cover Change Matrix
To understand and analyze the Change Detection results, the Land Cover Change Matrix shown on the right was utilized.
This matrix clearly outlines how to interpret different land use landcover transitions to evaluate whether such transitions are possible in real life or are just errors of process/user.
The matrix can be read as:
- Highlighted Red - Land Degradation
- Highlighted Red with Red Text - Unlikely Transitions
- Highlighted Green - Improvement
- Highlighted Yellow - Stable/No Change
Source: Good Practice Guidance for SDG 15.3.1, United Nations Convention to Combat Desertification
Results
The Change Detection analysis revealed several trends, of which 10 are outlined below
As anticipated, urban expansion is in the lead with more than 75 km 2 of land transformed. The second most common trend noted was vegetation loss with cropland transitioning to Other Lands (bare land or built-up land which is not settlement). This however was followed by two positive changes with some areas previously classified as Settlements or Other Lands becoming vegetated. This accounts for more than 80 km 2 of land area.
Results
Land Consumption Rate (LCR)
On the other hand, LCR for the city of Harare shows a positive trend as the rate has decreased when compared to the same time in 2015.
While both the total area built up and the population of the city has gone up, the rate at which land is being transitioned or consumed is still relatively low.
Analysis
While the LCR is less than what it was in 2015, it does not mean that all is well. Urban expansion is still occurring at an alarming rate leading to vegetation loss. The transition of Cropland to Other Lands is also quite concerning as this means land is being cleared (often leading to more Settlements).
In addition, an increase in vegetation around Settlements has been noted in the central and north-east sections of the metropolitan, but if this equates to greater vegetation growth needs to be corroborated with ground truth data.
It would also be great to have one more dataset between 2015 and 2023, preferably either 2018 or 2019, to get more insights on these trends.
Conclusion
The city of Harare has significantly developed since 2015 however, the Land Consumption Rate has slowed down. This can be interpreted as good news for the city however, more analysis needs to be conducted to get the full picture. Some trends which show unsustainable land use practices and land degradation in Harare have been noted but this needs to be corroborated with rectified ground truth data.
The Good Guidance Practice by UNCCD is a great tool for conducting similar analyses below the national level however, good training datasets can make a huge difference in the efficiency of the process and overall results/outputs.
