a S c i T e c h n o l j o u r n a lResearch Article

Murungweni, Geoinfor Geostat: An Overview 2013, S1http://dx.doi.org/10.4172/2327-4581.S1-015

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Effect of Land Use Change on Quality of Urban Wetlands: A Case of Monavale Wetland in HarareFlorence M. Murungweni1*

Abstract

This study seeks to assess the effects of land use change to the quality of urban wetlands using Aerial Photography and Geographic Information System software. In this study urban community that surrounds Monavale wetland, Birdlife Zimbabwe a non-governmental organization, Harare city council and the Department of Natural Resources were used as research subjects. A questionnaire, Geographic Information System and secondary data were used as research instruments. Aerial photographs of August 1984 and 1995, topographical maps and survey records from Surveyor-General’s Office were used to provide information on the spatial extend and various land uses within the wetland area. The study showed that about 13.4% of the wetland has been lost either to cultivation, construction or recreational activities. These activities have had detrimental effects to the wetland biodiversity. Whilst part of the wetland has been conserved, the remaining greater part is seriously being degraded by various human activities. The study recommends that the environmental organizations such as Environment Africa and Birdlife Zimbabwe should sensitize urban farmers at Monavale as well as construction companies of the impact of their developments to the wetland biodiversity and worse still to Lake Chivero, in the downstream. The study also recommends that the City of Harare, Ministry of Environment and Tourism, non-governmental organizations such as Birdlife Zimbabwe and Environment Africa as well as Monavale community work together to conserve the wetland from further degradation. Policies that have been formulated by the government of Zimbabwe in the conservation of urban wetlands need to be fully implemented if the wetland could be saved for the benefit of the people, plants, animals and the soil.

Keywords

Wetland; GIS; Land use

*Corresponding author: Florence M. Murungweni, Saveteck Solutions, Masvingo, Stand N0 1073, Crowborough North, Mufakose, Harare, Zimbabwe, Tel: +263 772 255 504; E-mail: fmmurungweni@gmail.com

Received: April 10, 2013 Accepted: July 31, 2013 Published: August 09, 2013

flood control, water table maintenance and habitat provision for some plants and animals [1]. Urban wetlands provide with excellent sites for educational studies of biology and ecology. They also provide with important recreational facilities such as sites for bird watching, canoeing, duck hunting and fishing. Urban wetlands provide an important breeding and nursery areas for a large range of animals that include birds, fish and invertebrates. They also improve water quality downstream by removing nutrients and other pollutants in the water or attached to the sediment as the water passes through the wetland. By removing nutrients, wetlands decrease the likelihood of algal blooms forming further downstream. Different people of different communities view urban wetlands in different ways throughout the whole world. Whilst some take them as places of agricultural importance, others view them as areas of ecological importance thus they should be preserved from agricultural practices.

Despite their importance, urban wetlands are now subject to many pressures that result in their loss or degradation. The threats of urban wetlands range from urban sprawl, infrastructure development, siltation, unregulated recreational activity, pollution from human waste and industrial effluents or diversion of water for irrigation, domestic or industrial use. Today resources are threatened as wetlands are drained, filled and fragmented, embankments are built and water supplies are diverted and infrastructures such as residential houses are established on these wetlands [2]. These developments can close the drains that feed the wetlands and can prevent flooding which is vital for the functioning of the wetlands. Major threats to urban wetlands are population growth and urban development, nutrient enrichment and ignorance [3]. Ignorance is a major factor threatening wetlands as one would not know the benefits of wetlands when maintained in their natural state. Threats to urban wetlands may result in loss of wetland habitat, deterioration in quality of water or loss of aesthetic values.

Although wetland scientists and managers have worked to increase public awareness of the importance of urban wetlands, in recent years, regulations to protect wetlands have been weakened and in many urban areas wetlands continue to be lost to development [4]. The qualities of urban wetlands seem to be related to the land use activities that are practised by urban dwellers in the wetland area. Monavale wetlands are not spared from these developments as they forage seasonal birds and other water habitats. The research seeks to establish if human activities such as cultivation and construction have any effects on the quality of Monavale wetland.

Statement of the problem

People’s intrusion into the wetland of Monavale through cultivation and construction has resulted in disintegration of biodiversity and degradation of the wetland. The wetland is an important breeding and foraging ground for a number of migratory birds and also a source of water for Harare’s main water supply, Lake Chivero. Many researchers recognize functional values of urban wetlands but few studies have attempted to attach economic values to them both at regional and national level. This research project is aimed at coming up with information on the way in which cultivation and construction are detrimental to the distribution of wetland

Introduction Background to the study

Urban wetlands in their undisturbed state are ecologically healthy since they can help maintain biodiversity, water quality and water quantity as well as fulfilling human aesthetic, recreational and other social needs. The ecological functions of urban wetlands include

Citation: Murungweni FM (2013) Effect of Land Use Change on Quality of Urban Wetlands: A Case of Monavale Wetland in Harare. Geoinfor Geostat: An Overview S1.

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biodiversity at Monavale. The findings of the study are important for the implementation of strategies that could be used to conserve the wetland and its habitats, which include plants and animals.

General objective

To make an assessment of the effect of urban land use change on quality of wetlands in Monavale area using geo-information tools (Table 1).

Study area

Monavale Wetlands are found to the North- West of Harare, approximately 12 kilometres from the city centre. The actual study area is bordered by Lyndhurst Road into Richwell Avenue, then Sherwood Drive into Marimba river and it passes through the left bank of the river along the cadastral boundary of the Meadows and finally through Mayfield Estate back into Lyndhurst Road. In terms of the hydrological zones of Zimbabwe, Monavale falls in Zone C. The river system of this zone drains the northerly direction. Marimba River that passes through Monavale form dendritic pattern as it drains to Lake Chivero.

Monavale falls in region 2 of intensive agriculture farming according to agricultural regions of the country. This region receives high rainfall of between 700-1000 mm per year. Temperatures are warm in summer to about 18-22 degrees Celsius and cool winters. The Figure 1 above outlines the geographical location of the study area.

Research Methodology The section focuses on the research design, research instruments,

data collection procedures, data presentation and analysis that were used in conducting the research.

Research design

In this research the researcher used qualitative research design in conjunction with GIS to identify land use changes in Monavale and their effect to the natural environment. This descriptive approach is very important in research and is attractive because of its massive use of words that are a specialty of most humans [5].

Aerial photographs of at least a decade apart, 1984 and 1995, at 1:25,000 scale were used in this research. Survey records showing subdivisions that were done in Mayfield park, 1:5000 topographical map to show the topography of the area and the Harare street map that shows study area were obtained from Surveyor-General’s office in Harare. The researcher also used the Harare Master plan from city council that shows various land uses within the study area. A

questionnaire was also used to collect data on Monavale wetland cultivators that were also used to assess quality of wetland. The questionnaire was designed to collect information on the residential suburb of the farmer, condition of farmer’s crop field, and period of cultivation, total area of the field, quantity of yield and if the farmer continued cultivating the wetland. Other important information obtained included the chemical inputs that were used in cultivation, ways used to reduce the effects of flooding. The questionnaire was administered on 25 Monavale urban farmers cultivating in the wetland. Key informants such as Birdlife Zimbabwe, and the surrounding community that have interest in the wetland provided necessary information through informal interviews.

GIS was used to assess the changes on state of wetland. GIS tool was selected because it is capable of overlaying themes from different time periods to produce description of land use change over time. ArcGIS software was used in digitizing and analyzing data. Ms Excel was used for data analysis of tabular data.

Subjects

The selection of the population in this study considered those who participate in various activities in the study area. It consisted of the urban community within the study area. It includes also Birdlife Zimbabwe, a Non-Governmental Organization (NGO) that is interested in the conservation of migratory birds within Monavale wetland. The Harare City Council, that is responsible for the allocation of urban land for various activities and finally the Department of Natural Resource that is concerned about the conservation of wetlands in the country. GIS and Interviews and Questionnaire Surveys were used as research instruments. Secondary data constitute of 1:5000 map and survey records from Surveyor-General’s office.

Specific Objectives Research Questions

To identify land use change in Monavale wetland over 1984 and 1995

What is the spatial extent of the wetland?

To assess the changes on Monavale wetland biodiversity.

What is the relationship between human activities and the quality of wetland

To establish wetland utilization by Monavale residents.

How do the resident communities use wetland?

To relate the effects of the land uses to the quality of Monavale urban wetland.

What biological changes have occurred in Monavale?

To recommend measures to improve quality of urban wetlands

To what extend are the existing legislations protecting wetlands?

Table 1: Show specific Objective and Research Questions.

Source: Street map of Harare, S urveyor-General (2002), Scale 1:30,000.Figure 1: Map of Study Area.

Citation: Murungweni FM (2013) Effect of Land Use Change on Quality of Urban Wetlands: A Case of Monavale Wetland in Harare. Geoinfor Geostat: An Overview S1.

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Aerial photographs taken almost a decade apart (1984 and 1995) at the scale 1:25 000 were used. All data available was gathered and analyzed. Written documents and some information were accessed from the following sources:

• City Council provided with the information on development of area and the developer name.

• Birdlife Zimbabwe provided with key informants that have more detailed information on the wetland and how they maintain it to conserve the birds.

• Department of Surveyor-General: Aerial photographs, Survey records, Harare Street Map and 1:5 000 topographical map.

Questionnaires survey was also used in collecting data. A structured questionnaire was designed to collect information on the wetland utilization by cultivators at Monavale Vlei. Farmers were interviewed from their fields to avoid gathering information outside the study area. The researcher self-administered the questionnaire. The researcher visited the study area for three days and these were spread randomly for three weeks so as to meet different cultivators as they harvest from their fields. Questionnaires was either filled by responded or the researcher who could translate the questionnaire into Shona (local language) for interviewees who could not read and/or write.

Time series data collected for 1984 and 1995 was analyzed by tabular and graphical presentation in Excel. The aerial photographs were scanned, geo-referenced and vectorised using ArcGis software.

Data Analysis and PresentationData obtained from the review was subject to qualitative and

in few cases semi-quantitative analyses. GIS as a tool was used to identify various land uses within the wetland and gather all pertinent information and measurements. Photo interpretation method was used to identify features. ArcGIS was used in analyzing the data of various land uses and each land use extend was also given. From the GIS and photo interpretation process the following land uses were identified: Residential, Wetland, Cultivation, Water bodies/rivers, Recreational. 1:5000 map was useful in confirming the features identified from aerial photo interpretation and GIS. Data, information and knowledge gathered are presented in the form of graphs and tables, maps and explanations provided.

Results and DiscussionsResults show the effects of land use changes that have occurred

in Monavale in the years 1984 and 1995 as a result of residential and recreational expansion. Land use data from the two series of aerial photographs showed vivid differences in land use over the decade. Figure 2 shows the wetland area and multiple layers of land uses overlaid to produce a composite land use map for Monavale for the year 1984. Figure 3 show additional changes that have occurred over the time compared to Figure 2.

Urban agriculture in 1984, was practiced all over the wetland area. Of particular importance is the horticulture garden that produce flowers and herbs, it is shown in green colour and is just adjacent to the banks of Marimba River.

By 1995 part of the wetland had been surveyed to pave way for the construction of Mayfield Park an additional residential area.

Strathavern residential area expanded into the wetland as shown in Figure 3. Survey records from the Surveyor-General’s Office show that apart from houses already constructed within the wetland, flats are also to be constructed within the same area. Part of the wetland is now a conserved area where natural forest is allowed to regenerate and is owned by NGO, Birdlife Zimbabwe. The conserved area is shown in green colour in Figure 3. Comparison of 1994 and 1995 land use changes are illustrated in Table 2. In Table 2, most change was in the loss of wetland to residential by 8.1%. Generally the wetland was lost by 13.4%.

Effect of residential and recreational expansion on urban wetland biodiversity

From information provided in Table 2, Residential area occupied 97 hectares in 1984 and had increased to 124 hectares by 1995. Due to the increase in population of the urban area and the demand for housing inevitable hence the municipality had to convert part of the wetland to residential area. According to Auret [6] Harare City Council’s housing waiting list was 50 055 by 1989 up from 36 457 in 1984. This reduction in wetland area results in extinction to particular species such as migratory birds, frogs, reeds or grass.

Figure 2: 1984 Aerial photography extend of land use.

Figure 3: 1995 Aerial photography showing spatial extend of land use.

Citation: Murungweni FM (2013) Effect of Land Use Change on Quality of Urban Wetlands: A Case of Monavale Wetland in Harare. Geoinfor Geostat: An Overview S1.

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Land use Type 1984 area in hectares Percent (%) 1995 area in hectares Percent Percentage change

Residential 97 28.8 124 36.9 8.1

Recreational 7 7 24 7.1 5

Horticulture 5 5 6 1.8 0.3

Wetland 227 67.6 182 54.2 -13.4

Total 336 100 336 100

Table 2: Comparison of Land use changes between 1984 and 1995.

The increase in residential areas is also attributed to the government that targeted housing for all by the year 2000. This policy stimulated private developers to construct houses to the people at a lower cost. Hence more houses were constructed within the decade in order to meet public demand. The opening of the banking sector in the provision of mortgage loans to the low-income bracket greatly contributed to the increase in demand for residential land. Many people benefited from these housing programs that were donor funded by USAID during this period. It is also this provision of houses to people that resulted in the conversion of the wetland to residential land use. Mayfield Park houses are constructed barely 10m from the river. Development of houses in this area has impacted negatively on the natural functioning of the wetland. As indicated on 1995 photography, the flooded area is shown and surprisingly that is the same area where houses have been constructed. In a good rainy season the houses will be flooded with water as currently they are cracking. From the findings obtained from the lobby groups such as Birdlife Zimbabwe, Environment Africa as well as Harare City Council, no Environmental Impact Assessment was done for Environmental Management Act (EMA) was not yet in place in the country.

According to the Town Planning Section of the city council, all open spaces such as wetland areas are reserved for recreational purposes. From Figure 2 and Table 2, it can be seen that there was great expansion on the sports field from 1984 to 1995. However recreational facilities do not damage the wetland area as much as other land uses do. The recreational facility increased by 8.1% from 2.1%.

Human utilization patterns of the wetland

As was highlighted earlier on, the practices of agriculture that are taking place at Monavale wetland fragmented this wetland habitat into grassland and cropland.

Most of the farmers cultivated the wetland for at least 10 years and most of them owned more than one crop field. Individual plots are small with a mean size of between 0.25-0.5 ha. Although a range of crops is grown the vast majority of the cultivated area is located in permanently waterlogged parts of the wetland and is occupied by maize and sweet potatoes. Table 3 above shows the major crops that are grown in the wetland. About 68% of the crop fields were in the flooding zone of the wetland as shown in Figure 4.

Effect of cultivation implements and chemicals used on biodiversity

Most cultivators use hoes and all crop fields were dug in order to loosen the soil for crop roots to penetrate easily. There was only one person who used tractor to prepare his crop field. 60% used ammonium nitrate and compound D or urea fertilizers in their fields.

About 40% used organic manure to improve nitrogen content of their fields. Some crops had signs of lack of nitrogen (leaf chlorosis). Fertilizer is applied more than 4 times since most of it is leached into Marimba River as fields are adjacent to it.

The effect of cultivation on wetland biodiversity

With the current wetland use pattern, (distinct grassland and cropland) crop cultivation had taken up a considerable area especially the water logging area that is used by birds when breeding. The clearing of the land in preparation for agriculture has also impacted heavily on the natural scenic view of the area. Trees, reeds and grass are cut, thus disturbing the wetland area. Most crops about 68% were highly flooded with several open pools of water. Cultivators disturb the wetland further by their system of early planting and ridging as a technique to cultivate the flooded patches of the cropland. This however results in the loosening of the topsoil and when the river floods, it erodes the soil thus increasing river siltation.

Monavale wetland is a seasonal wetland that floods only in summer. The existence of the vegetable and herb production in this wetland would further threaten on the quality of the wetland. Fertilizers and chemicals that are applied in the garden infiltrates into Marimba River. It then causes eutrophication of the aquatic life, not only in Marimba River but also down to lake Chivero. A report in Herald of 30 January 2007 showed that fish in Lake Chivero died at the mouth of Marimba River.

Summary, Conclusion and RecommendationsThe effects of land use change on the quality of urban wetlands

greatly affect the biodiversity in general. It is thus necessary to implement correct measures to redress urban wetland loss.

Maize only Maize & sweet potatoes

Maize & other crops

Flooded crop fields 3 10 4

Unflooded crop fields 2 4 2

Table 3: Major crops grown in the wetland.

Figure 4: Flooded and unflooded patches of the cropland.

Citation: Murungweni FM (2013) Effect of Land Use Change on Quality of Urban Wetlands: A Case of Monavale Wetland in Harare. Geoinfor Geostat: An Overview S1.

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Summary of findings

This study centered on assessing the effect of urban land use change on quality of urban wetlands in Monavale area, Harare. The results showed that the fragmentation of the wetland through housing development and crop cultivation had a significant disturbance on the biodiversity. A loss of about 13.4% of the wetland area to these human activities shows that the biodiversity of the area has also been negatively affected. Destruction of the grassland area mostly disturbs animals such as wetland birds since their habitat area will have been reduced. Previously the wetland was 227/ha and has been reduced to 182ha now. This can be a sign that there is serious fragmentation of the wetland. Since 11ha have been recovered for conservation, it is thus never too late to save the rest of the wetland as the lobby groups have already successfully initiated the conservation of part of this wetland. It was however not an easy study to carryout for cultivators were generally unwilling to divulge more information about their farming activities. This was so as they were afraid to lose their small fields to the so called environmentalists as the case at Monavale. Most cultivators pretended that they did not know that cultivation in riverbanks causes river siltation. However besides these constraints, some interesting findings and observations were made in this research.

Recommendations

In the light of the above conclusions, the following recommendations have been made:

• There is need to conserve the wetland at Monavale for the continued benefit of biodiversity as well as people in the long run.

• The government of Zimbabwe formulated some policies in the conservation of such areas as wetland and these need to be implemented if the wetland could be saved for the benefit of people, plants, animals and the soil.

• It is rather expensive to restore degraded wetland but it is achievable. There is need for the environmental organizations such as Bird life Zimbabwe, working at this wetland to demarcate the most sensitive areas of the wetland and lobby to protect the areas from further degradation through cultivation and construction. This would help to have a more natural condition for animals and plants to grow.

• The environmental organizations should sensitize the farmers at Monavale and construction companies of the impact of their activities to the environment and downstream.

• Residents surrounding the wetland should be encouraged to set up site support groups (SSGs) so as to allow the environmental organizations working in this wetland to be able to communicate with the people more easily. As this method was successfully done at Monavale vlei. The same can be done to the rest of the wetland area. To date the City of Harare (Urban Planning Section) is currently discouraging urban farming especially along riverbanks and this should be followed in order to conserve our environment.

References

1. Gren IM, Groth KH, Sylvénc M (1995) Economic values of Danube floodplains. J Environ Manage 45: 333-345.

2. Khan HM (2004) Haors, baors and beels: sources of livelihood in Bangladesh. World Conservation- Voices of Asia 2: 20.

3. Noort R, Fletcher W, Thomas G, Carstairs I, Patrick D (2002) Monuments at Risk in English Wetlands. English Heritage, University of Exeter.

4. Santelmann MV, Larson KL (2004), WETLANDS, The Society of Wetland Scientists, 24: 717-718.

5. Gwimbi P, Dirwai C (2003) Research Methods in Geography and Environmental Studies. Zimbabwe Open University, Harare.

6. Auret D (1995) Urban housing: A national crisis? : Overcrowded and inadequate housing and the social and economic effects, Mambo Press, Gweru, Zimbabwe.

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Author Affiliation Top1Saveteck Solutions, Masvingo, Zimbabwe