8. Crab collection

Mapping Agriculture Land in Bangladesh: Hybrid Classification of Landsat Satellite Imagery from 1976 to 2010

DI DIGITAL INTERPRETATION OF SATELLITE IMAGES

POST CLASSIFICATIONLASSIFICATION

GIS ANALYSIS

TRENDS OF AGRICULTURE LAND AVAILABILITY (1970s-2010s)

Class combination

Class clumping

Class generalization

Ground truthing Error correction

Removal artifacts

Combine tiles (16 scenes)

Class overlay and mapping

Generate area with statistics

Cartography & map outputs

Cross tabulation

statistics

OUTPUTS

SATELLITE IMAGES (Landsat 1970s - 2010s)SATELLITE IMAGES (Landsat 1970s - 2010s)

Unsupervised Classification

Statistical clustering of land cover types

on the basis of spectral reflectance

Separate land cover types into different

classes

Some land classes remain mixed•Separate land cover types into sses

•Some land classes remain mixed

Supervised Classification

Incorporation of human knowledge on the land

cover types for increasing accuracy and

precision

Select ROIs from known land cover types

Several ROIs from each land cover type

Machine Intelligence Machine + Human Intelligence

Land Cover Type Year 1976 Year 2000 Year 2010 Annual trends of change in

land use (%)

Area (ha) % of total Area (ha) % of total Area (ha) % of

total

1976-

2000

2000-

2010

1976-

2010

Agricultural Land: 13303654 91.83 12742274 87.69 12176904 83.53 -0.172 -0.416 -0.244

Cropland 9761450 67.38 9439541 64.96 8751937 60.04 -0.101 -0.493 -0.216

Forest 1754917 12.11 1311121 9.02 1434136 9.84 -0.129 0.081 -0.067

Mangrove forest 452444 3.12 486791 3.35 441455 3.03 0.009 -0.032 -0.003

River 911819 6.29 888441 6.11 939073 6.44 -0.007 0.033 0.004

Lake 50829 0.35 58261 0.40 51739 0.35 0.002 -0.005 0.000

Beel and Haor 239977 1.66 251774 1.73 250727 1.72 0.003 -0.001 0.002

Aquaculture 582 0.01 143506 0.99 175663 1.20 0.041 0.022 0.035

Tea estate 119847 0.83 138533 0.95 96152 0.66 0.005 -0.029 -0.005

Salt pan 11789 0.08 24306 0.17 36022 0.25 0.004 0.008 0.005

Non-Agricultural Land: 1183605 8.17 1788307 12.31 2400867 16.47 0.172 0.416 0.244

Rural settlement 885637 6.11 1458031 10.03 1766123 12.12 0.163 0.208 0.177

Urban & Industrial 26799 0.19 47495 0.33 87616 0.60 0.006 0.027 0.012

Accreted land 271169 1.87 282781 1.95 547128 3.75 0.003 0.181 0.055

Total 14487259 100.0 14530581 100.0 14577771 100.0 - - -

M. Nazmul Hasan1, M. Shahadat Hossain2, M. Abdul Bari1 and M. Rafiqul Islam3

1Soil Resource Development Institute, Ministry of Agriculture, Dhaka, Bangladesh, 2Institute of Marine Sciences and Fisheries, University of

Chittagong, Bangladesh, 3Department of Agronomy, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh

INTRODUCTION

Agriculture has a strategic function, because it is a main food supplier for the people

in Bangladesh. Different estimation methods of agricultural production provide various

data and information, so their reliability is questionable. The information regarding the

shifting rate of agricultural land to non-agricultural use has been reported to be about

1% per year (UNDP 2003). This rate of shifting however does not seem to have a

sound scientific basis. In fact, if this number were correct, at least one quarter of the

country’s agricultural land would have been lost since independence (1971). Careful

assessment of the changing agricultural system and environment is an essential first

step to understanding current and future food security issues of Bangladesh.

Geographic information system (GIS), which is strong capacity in data integration and

analysis and visualization, become the main tool to support LUP approaches.

Therefore, this research aims at detecting changes in agricultural activity and

environment using remote sensing technology. More specifically the research

objectives are to a) quantify how the availability of agricultural land has evolved since

independence; b) quantify how the availability and allocation of the total land to the

various uses has evolved at national levels since independence; and c) quantify land

lost and gained due to various factors.

The study has been conducted through (i) digital interpretation of satellite imagery (ii)

secondary information and (iii) ground thruthing in selected locations of Bangladesh. A

total of 16 scenes of Landsat MSS and TM/ETM imagery from path 135-139 and row

42-46 covered the entire Bangladesh have been analyzed digitally. Space-borne

satellite imageries (Landsat, MSS/TM/ETM) available between 1976, 2000 and 2010

were used to identify the types of land available in different locations of the country

and quantify the changes with geographical distribution of arable agricultural land.

METHODS

Fine tuning of land cover classes

Export classes to vector (Raster to vector)

Prepare mapping format (shape file)

Results of this study indicated a declining trend of agricultural lands from

13,303,654 ha in 1976 to 12,742,274 ha and 12,176,904 ha over the years of

2000 and 2010 respectively. A total of 561,380 ha agricultural lands were lost

during 1976-2000 and this figure was increased to 565,370 ha during 2000-

2010. Yearly average loss of agriculture lands were 23,391 ha (0.17%) and

56,537 ha (0.42%) during 1976-2000 and 2000-2010 respectively. This

indicates that agriculture lands were shifted to other uses in higher rates

between the years of 2000 and 2010. The geo-spatial distribution of agricultural

land was evaluated against ground truthing data and the accuracy level was

92%, indicating a good consistency with existing agricultural land of the country.

The results of the analysis produce science-based and up-to-date data on the

availability of agricultural land including trends of land cover change during

1976-2010. Thus, an efficient and sustainable land use plan is required to

reduce the agricultural land use changes related to farming and food security.

CONCLUSIONS

RESULTS

POLICY IMPLICATION

The growth of rural settlement is the main driver of the land loss from crop

agriculture followed by urban and industrialization. Houses of ever increasing

population in Bangladesh are expanding towadrs agricultural land. As the food

security is the main concern of Bangladesh, necessary steps should be taken to

conserved agricultural land from the shifting to non-agricultural land uses.Land cover dynamics at national

level during 1976-2010

Year 1976 Year 2000 Year 2010

Geospatial extent of cropland and forest land cover maps of Bangladesh

representing declining trends

Geospatial extent of rural settlement, urban and industrial area and accreted land

cover maps of Bangladesh representing increasing trends

Geospatial extent of water bodies and mangrove forest land cover maps

of Bangladesh representing relatively stable

An analysis of major land cover types in Bangladesh during 1976-2000-2010 periods

derived from Landsat imagery