Transformation of agricultural land and waterbodies in rapidly urbanising Bangladesh: recognising the extent of sustainability concerns

Transformation of agricultural land and waterbodies in rapidly urbanising Bangladesh: recognising the extent of sustainability concerns

PrincipaI Investigator:

Dr Bowei Chen, Aerospace Information Research Institute, Chinese Academy of Sciences

Collaborators:

Khulna University, Khulna, Bangladesh (Dr Shilpi Roy (CO-I), Associate Professor of Urban and Rural Planning)

Overview

Bangladesh has a high dependency on agricultural land and water bodies.  However, the spontaneous urbanisation process over the last 30 years has been taking over these invaluable ecological assets. This study reflects on the urban transformation in the top 10 rapidly urbanising cities and their peripheries in Bangladesh between 1991 and 2020 and traces the impacts of urban growth on agricultural land and water bodies and associated sustainability challenges. Using time-series satellite imagery, interviews and photographic analysis, the team identified the areas that have observed the most changes, related driving forces responsible for these changes and their implications on the life and livelihoods of people.

This project finds the extent, rate and pattern of urban growth and changes in agricultural land and water bodies in Bangladesh and further informs how these changes affect livelihoods and challenge environmental sustainability. Findings in blogs, policy briefs, easily accessible dashboards and journal papers will inform policies and practices towards sustainable urbanisation in Bangladesh.

Innovative programming-based methods applied in this research for image downloading, image classification, analysis of classified images, and data visualisation were shared in a public workshop in March 2022 that enhanced the capacity of the early career researchers for improved, accurate and efficient monitoring of the changes of land use that have implications for sustainable development.

The project team fulfilled the planned objectives in the following ways:

1. Assessing the extent, rate and pattern of urban growth and changes in agricultural land and water bodies for the past 30 years:

Based on several indicators, the team selected the top 10 urbanising cities in Bangladesh and the areas surrounding these cities with possibilities of urbanisation in the next 20 years.

For producing reliable and repeatable results in a short time, they developed a fully automatic approach using the open-sourced R programming software to implement the process of downloading cloud-free satellite images, calculation of indices from these images, attribution extraction, feature selection and land use classification.

Classified time-series images, change detection, distribution of changes in space and concentration of land cover in different years show the extent, rate and pattern of urban growth and changes in agricultural land and water bodies in 10 major cities for the past 30 years.

2. Exploring forces of urban growth and its implications on livelihoods and the environment:

The team visited 114 areas, each with an area of at least 2.5 sq. kilometres, in 10 cities and their peri-urban areas where major urban growth has been observed. They interviewed 345 people from these areas and gathered photographs to trace the forces of urban growth, changes in livelihoods of the people here and experience and potential challenges related to environmental sustainability.

3. Contributing to attaining SDG 11 and spread the impact:

Dr Chen presented some of the initial findings on behalf of the whole team during the 5th Quantitative Remote Sensing Forum, the biggest remote sensing international conference in China. Over 300 people attended the session to listen to the latest findings of Bangladesh and its contribution to SDGs.

In addition, Dr Chen’s host institution inaugurated the International Research Centre of Big Data for Sustainable Development Goals (CBAS) this year. The capacity building through this funding will strengthen the collaboration between the teams on both sides, and this study will be presented as a case of successful international collaboration.

4. Enhancing capacity

The innovative programming-based remote sensing methods applied in this research were shared in a public workshop in March 2022. Early career researchers in Dr Shilpi’s host institution, Khulna University, also learned about these new methods through two technical sessions. In addition, a team of 26 early career researchers from Bangladesh who were involved in the interview and photographic data collection, data cleaning, data analysis and interpretation, now have the skills of applying the qualitative tool in urban growth studies. Most of these researchers are graduate urban planners working for SHLC and national non-government organisations.

This project responds to rapidly diminishing agricultural lands and water bodies in a DAC listed country, Bangladesh. This contemporary issue challenges sustainable urbanisation and, therefore, will contribute to the thinking, studies and policymaking reality of the DAC listed countries. Moreover, there is little research on the national scale impact of urbanisation and its consequence on food and water. Therefore, the implementation of this project helps contribute to SDG 11: Sustainable Cities, in the context of the rapid urbanisation of developing megacities.

The project team formed an integrated remote sensing dataset of the study area from cross-sensor Landsat images. They developed a cloud-free composite algorithm based on the Google Earth engine platform to produce pixel-level cloudless, seamless, and clear images to extract maximum value from these innovative datasets. Furthermore, they have developed fully automatic tools using the open-sourced R programming software to implement the analysis for reliable and repeatable results with the great reduction of human interactive time, providing the capacity towards a continuous monitoring system to quantify land-use changes.

This project will allow Dr Shilpi and her team to be included in the DBAR-Coast network as well as in the newly founded International Research Centre of Big Data for Sustainable Development Goals (CBAS).

Dr Chen received the Young Talents of Science and Technology Innovation award by the Hainan Association for Science and Technology in Sep 2020. This has a follow-up funding focus on social sensing data mining for the foreign study areas, and Bangladesh has been chosen as a case.

The project team assessed the extent, rate and pattern of urban growth and changes in agricultural land and water bodies in the top 10 urbanising cities in Bangladesh (Dhaka, Gazipur, Chattagram, Barisal, Comilla, Coxs_Bazar, Khulna, Mymenshing, Rajshahi, Rangpur and Sylhet) since 1991. They have also explored how these changes are affecting livelihoods and challenging environmental sustainability.

Major findings are follows:

1. All ten major cities in Bangladesh have been in a phase of rapid urban growth over the past three decades, of which Barisal, a secondary city, has the highest annual urban growth rate of 37.78 over the past 30 years, while for this period Dhaka has observed the highest gain of built-up area of 73.60 sq. kilometres.

2. All the cities are sprawling rapidly. Alarmingly, the annual urban growth rate in the outskirt of Rajshahi has been as high as 4702 since 1991. Between 1991 to 2020, peri-urban Dhaka has sprawled areas of 237.44 sq. kilometres.

3. Irrespective of the city types, growing built-up areas are taking up the invaluable farming lands in all cases. Larger cities will have a stronger negative relationship between these two classes. Peri-urban Dhaka has lost about 263 sq. km of farming land over the last three decades.
4. The loss of water bodies within the city is highest in Dhaka. Since 1991 the city has lost about seven sq. km. of water bodies. However, peri-urban areas of the three major cities Dhaka, Khulna and Rajshahi, have gained an average area of more than 20 sq. km. of water bodies over the last three decades.
5. In the process of urbanisation, the balance and dynamics of the urban area, vegetation and farmland can be used to cluster different city groups. The transformation among different classes results in similar behaviour that can be clustered accordingly.

The results above highlighted the changing areas and allow the team to do field visits to understand the driving force and mechanism of this transformation and further the impact of everyday living for local people.

6. As few as five forces to as many as 22 have influenced sprawling patterns and processes in the study areas. Fundamental forces include industrialisation, transport network expansion, employment opportunities, increased housing demand, land development by private and public authorities, low land value and low living cost.
7. The urbanisation process has resulted in the extinction of cultivable water bodies, decreased soil fertility, and increased farming costs, leading to the loss of agricultural production. As a result, residents now suffer from the unavailability of freshwater, waterlogging, income loss and shortage of agro-food supply. In many cases, marginal farmers sell their agricultural land and migrate to the nearest large cities.
8. However, people adapt to the changing land use pattern by shifting their occupation and using fertilisers, pesticides, hybrid seeds, and new crops with high yields. Some farmers worked as day labourers in construction, factories, and rickshaw pooling.
9. Dhaka has gained the most policy attention concerning urban growth management. This research finds that the urban planning and national development policies should not underestimate the rapid growth of the secondary cities to aim for a sustainable future for Bangladesh’s cities.
10. Urban growth has improved the residents’ standard of living but degraded their quality of living.

Initial findings were presented at China’s biggest remote sensing forum and have drawn the attention of researchers and students for the very first time as this topic is not widely known to the domestic remote sensing community, especially in the context of sustainability. In addition, with the newly founded International Research Centre of Big Data for Sustainable Development Goals, the team will maximise the impact of this study through joint publications, media coverage and workshops. The follow-up workshop in knowledge transfer between top remote sensing communities from China and top urban communities from Bangladesh will lead to new insights for sustainable urbanisation.

Dr Shilpi’s team in Bangladesh was involved in all project stages, from signature extraction, signature verification, field checking of the classified images to collection of primary data from 114 areas that observed significant urban growth. Her team was also involved with transcription and analysis of 345 interviews and photographs to trace out the forces of urban growth, changes in people’s livelihoods due to loss of agricultural land and water bodies, coping strategies in place and potential challenges related to environmental sustainability.

The research team closely worked with the local people who lived in the areas that went through significant transformation for at least 30 years. In addition, people from different city regions shared their life experiences during data collection due to urban transformation.

Future research work will move towards the recent changes in the past five years with the support of the 3-m resolution Planet data from Dr Chen’s team. It will be interesting and worthwhile to look at how Covid-19 has impacted the land-use change and potential explanations.

The International Research Centre of Big Data for Sustainable Development Goals (CBAS) is an ideal channel to share the project findings and maximise the impact. Through the networking between Dr Shilpi and Dr Chen, the Bangladesh team will continue to be involved in this ambitious plan and expand the existing network significantly.

This project on a DAC listed country has strengthened the capacity of the researchers from both the partner institutions, one located in China and the other is based in Bangladesh.

1. Dr Chen’s team is mostly from urban geography. The techniques developed by Dr Chen’s team, such as cloud-free composite algorithm based on the Google Earth engine platform, and R scripts to automatically produce the classification result, has been beneficial to Dr Shilpi’s team for efficient and quality urban growth analysis.

Dr Shilpi’s team is from Urban planning background. With extensive knowledge about the cities under study they extracted a very large number of signatures on land covers that helped refine the algorithms for the classification and best represent the real scenario.

The application of qualitative tools in growth and impact analysis by Dr Shilpi’s team have helped Dr Chen’s team to better understand the driving forces of urban growth and the impacts of urbanisation. They have new insights about using mixed methods for the research on sustainable urbanisation.

2. Dr Chen is the liaison officer of the coast workgroup of the Digital Belt and Road (DBAR) Program, which was initiated by Chinese scientists, shares data, experience, technology and knowledge to realise the scientific mission of earth big data in the Belt and Road Sustainable Development Goals. This project will allow Dr Shilpi and her team to be included in the DBAR-Coast network for the sustainability study.