Vegetation are good measure of the health and quality of our environment, they provide social, economic and ecological benefits. Their beauty inspires writers and artists while their leaves and roots clean the air we breathe and water we drink among other things . The greater the vegetation cover and the less the impervious surfaces, the more ecosystem services are produced in terms of reducing storm, water runoff, increasing air and water qualities, storing and sequestering atmospheric carbon and reducing land surface temperature . A situation where the vegetation were being cleared off and being replaced by concrete surfaces, asphalt roads and building, the resultant effect is environmental degradation such as abnormal increase in land surface temperature causing thermal discomfort . Several published works have established the link between the urban land surface materials and the urban temperature characteristics. For example,  reported that land surface temperature was highest in urban residential areas where there were low vegetative covers while the lowest land surface temperature occurred in farmlands where there were high vegetative covers. According to , settlement growth reduces vegetative cover, thus, adds heat absorbing surfaces such as rooftops, asphalts and other concrete surfaces. Besides, greenhouse gases emissions from industries and automobile systems make the land surface temperature in residential and industrial land uses higher than that of vegetation and agricultural land uses . Studies have reported that vegetation provide shade which helps lower land surface temperature, they also release water to air through evapotranspiration processes which helps in the cooling system ,  and . Land surface temperature can be reduced even when there is settlement growth through planting of trees, because trees have cooling effects on the environment. Over the past three decades, Ibadan, the State Capital Metropolis of Oyo State in South-Western Nigeria is experiencing conversion of vegetation and agricultural land uses to residential, transportation and industrial land uses due to explosive population growth, industrialization etc, thus, resulting in changes in the land surface temperature. We therefore set out to investigate the relevance of tree planting and the creation of many urban green belts in Ibadan in order to reduce the problem of thermal discomfort in the Metropolis.
Land Surface Temperature (LST) is the temperature of the skin surface of a land. It is the surface radiometric temperature emitted by the land surfaces which can be derived from satellite information or direct measurement and observed by a sensor at instant viewing angle  Cited in . Land Surface Temperature (LST) is an important parameter in urban climatology; it can be derived from data sources such as Landsat. The thermal band of these sensors enables data collection on thermal properties of the land surface based on the amount of emitted energy. These data can be used to monitor land use/land cover change and land surface temperature over time . In this way, modeling the relationship between land use/land cover change and land surface temperature becomes possible.
1.1. The History of Settlement Growth in Ibadan
Ibadan, historically acknowledged as the largest traditional city in West Africa, has grown rapidly from a modest population of 70,000 inhabitants in 1856 to a cosmopolitan and densely populated city. The rapid development and spatial expansion of the city became pronounced during the period of Nigeria’s oil boom in the 1970s .
The Open Surfaces with natural land cover surrounding houses in the traditional core areas were change to built-up artificial land cover to provide more dwelling houses within the traditional family compounds as family units grew larger . Over the years, the inner core of the city grew by the process of densification which resulted into the emergence of informal settlements .
Land Use/Land Cover Changes in Ibadan became more rapid when it was made the headquarters of the defunct Western Region of Nigeria in 1946. It became a major Centre for attraction of many more expatriates and other Yoruba sub-ethnic groups due to the increasing range of job opportunities that abound in the Metropolis. Consequently, more residential areas were needed to accommodate the teeming inflow of people and the settlement began to grow rapidly . Ibadan, the State Capital Metropolis of Oyo State in South-Western Nigeria have changed from small, isolated rural areas to large, interconnected economic urban areas. This may be as a result of migration of people from rural area to it, in search of “greener pasture”. The establishment of University College in Ibadan in the year 1948 contributed enormously to the conversion of vegetation and open surface land uses to built-up land use.
1.2, Review of Similar Studies
The Land Surface Temperature before a settlement becomes urban area differs from what is obtainable when it becomes urban area. These differences are caused by the alteration of the earth’s surface by human activities such as construction which causes concrete, asphalt, metals and aluminums to replace natural vegetation. As a result of all these activities, changes occur in local weather and climate, one of the most familiar being the Urban Heat Islands (UHI) phenomenon  Cited in . The urban heat island is defined as the characteristics warmth of both the atmosphere and land surfaces in cities (urban areas) compared to their non- urbanized surroundings . Most cities are experiencing increase in temperature when settlement growth changes the characteristics of the earth’s surfaces to artificial concrete and impervious surfaces.
A lot of studies have been reported on the use of Remote Sensing and GIS to study the relationship between land surface temperature and land use/land cover changes. For example,  analyzed land surface temperature changes in response to land use/land cover change in Sangong River Basin in China. The author selected two images of Landsat TM/ETM + which belong to 1990 and 1999. Mono-window algorithm was used to get land surface temperature of 1990 and 1999, then changes of LST from 1990 to 1999 were gotten by using Arc/info 9.0 (ESRI, Arc GIS Desktop). The author also got the average LST through the weight and Standard Deviation of pixel by pixel in each land use in 1990 and 1999. Based on mean LST values, he calculated LST change rate per land use between 1990 and 1999. He found that land surface temperature is in remarkable response to land use/land cover change and that land surface temperature rose about 100C within 1990 and 1999. Another example is that of  who reported an investigation into the application of Remote Sensing and GIS on how land surface temperature responded to urban growth. The authors retrieved spatial patterns of land surface temperature and land use/land cover for 1992 and 2006 from Landsat images dated 16th August, 1992 and 19th May, 2006. They classified TM images into five land use types, including built-up land, water, barren land, forest land and agriculture land. Then, they characterized the land use types with remote sensing indexes. Normalized Difference Built-up Index (NDBI) is an indicator for urban area, Normalized Difference Vegetation Index (NDVI) as greenness indicator and Modified Normalized Difference Water Index (MNDW) was selected to represent water areas. They overlay classified land use maps and derived LST layers to recognize their spatial pattern to do correlation analysis. To examine the effect of land use/land cover change on land surface temperature pattern, land use change detection was performed. Changed areas were then overlaid with LST layers to calculate the LST differences between 1992 and 2006. Correlation analysis between land surface temperature and three mentioned indexes separately was done and then used two global and local multivariate regression to model LST based on indexes. Some of their results showed that land surface temperature increased by about 3.40C and 1.90C respectively for forest and agricultural land uses that were converted into built-up areas.
 reported an investigation into the application of the integration of Remote Sensing (RS) and Geographic Information Systems (GIS) for detecting urban built up growth for the period 1961–2002, and evaluated its impact on surface temperature in Baghdad city. Surface temperature, land cover pattern and Normalized Difference Vegetation Index (NDVI) were extracted from Landsat7 ETM + data. Land surface temperatures was linked to land use data of Baghdad region for further investigations of the relationship between temperature behaviour and urban structures. The Normalized Difference Vegetation Index (NDVI) was used to examine the relation between thermal behaviour and vegetation cover amount. The results showed that the negative average correlation more than 85% was identified by the results from the correlation and regression analysis of the extracted surface temperature from Landsat data image with NDVI. Also this research proved that the distribution of urban surface temperature depends on various land cover type of surrounding areas. Water and forest cover types show lower day temperature differences compared to residential, commercial cover types.
 employed the use of Remote Sensing and GIS techniques to identify the various land uses, their various transformations between 1986 and 2006 and measures the rate of urban expansion and loss of vegetation cover in Abuja, Nigeria. The study also analyzed the changes in Land Surface Temperature over Abuja area using Landsat TM and ETM + satellite data for 1986, 2002 and 2006. The emissivity per pixel was retrieved directly from satellite data and estimated as narrow band emissivity at the satellite sensor in order to have the least error in the surface temperature estimation. Strong correlations were obtained between high surface temperature and negative NDVI values. The study also revealed that the built up area has expanded by 17.88% of the total land area of Abuja in 1986 to 27.02% in 2006, vegetation covers reduced from 47.23–37.79%.
1.3. Sustainable City
Sustainability has become a much-needed target, especially when considering the rapid settlement growth and the subsequent exacerbation of social, economic and environmental problems . The notion of sustainable city emerged as a political initiative in response to the degradation that occurred in the urban environment throughout the twentieth century. Therefore, the issues related to the planning and management of human settlements were top priority of the United Nations Conference held in Stockholm in 1972 .
The UN sustainable city programme defined sustainable city as one that is able to retain the supply of natural resources while achieving economic, social and physical progress and remaining safe against the environmental risks that can undermined any development achievement. One of the global environmental problems is climate change. Combining sustainable development and urbanization issues together has become important because sustainable city is a prerequisite to sustainable development .
In sustainable city development, the primary goal is to make cities and their ecosystems healthy and sustainable over time in terms of their environmental, economic and social dimensions. This perspective gives birth to the concept of sustainable city . A sustainable city is a city that improves and enhances its natural, social and economic capital in ways that allow current and future inhabitants of the city to have healthy, productive and happy lives . A city designed with consideration of environmental impact, inhabited by people dedicated to minimization of heat and building city for healthy future.
As this metropolis is growing to meet the present needs, the needs of the future generations must also be put into consideration. Thus, a better understanding and practice of sustainable city can go a long way to preserve the natural landscapes of this city, even in the phase of urbanization. To achieve this, there should be an attempt to bridge the gap between nature and cities through what is called ‘Green Urbanism’ . Green urbanism is a practice of creating communities beneficial to human and the environment, an attempt to shape the cities and lifestyles that consume less of the world’s resources . A city with high air quality, moderate land surface temperature and minimize pollution of any type that will not totally eradicate the natural phenomenal in the environment because of settlement growth.