Abstract

  There is an increase in Deforestation on Zanzibar (Ungula) Island, particularly along the western side of the island.  Due to the island’s topography and climate, there is only a small portion of the island that is fertile.  This small portion is located on the western side of the island where there are deep soils, which are good for agriculture.  The eastern side of the island is mainly a coral rag area and has shallow soils.  Since the soil is poor on the eastern side of the island there is little to no agriculture and is used mainly for grazing [i].  Zanzibar’s economic dependence on agriculture has encouraged deforestation to increase the amount of land available for cultivation.  Recently, there has also been an increase in tourism.  To attract tourists, the island has marketed itself as a paradise-like destination.  To create the image of “paradise”, the island has been modified and changed to fit the “paradise” image [ii].  To create the image of “paradise”, coastal vegetation has been cleared to allow development of beach-front properties for resorts and docks which will allow cruise ships to visit the island.  This is only one example of how the island has been modified. For this paper, geographic information systems (GIS) and remote sensing images were used to study vegetative growth throughout the island.  Images were taken from Google Earth, Glovis, and Global Land Cover Facility.  These images were then modified and compared to other maps and images of Zanzibar.  After reviewing the images, I found there has been a noticeable decrease in vegetation.  The west side of the island has experienced the greatest decrease in vegetation.  Although deforestation appears to be concentrated on the west side of the island, deforestation is starting to increase in other parts of the islands.

Introduction

  Known as the best kept secret in the Indian Ocean, the island of Zanzibar (Unguja), lies about 25 miles East of the Tanzanian coast and 6 degrees south of the equator [i].  The island is about 60 miles long and 20 miles wide, taking up a total area of approximately 650 square miles [ii].   The island’s climate consists of humid tropical temperatures that range between 20°C and 40°C [iii]. The seasons are well defined with the hot and dry season from December to March, heavy rains from April to May, and the cool dry season from June to October [iv].  Zanzibar is mainly flat with its highest elevation being 120 meters.  The western side of the island is comprised of deep and fertile soils.  The eastern side is the opposite and has poor, shallow and less fertile soils.  The eastern side is mostly coral rag area, which has rough bush cover [v].  The coral rag grassland, bush, and forest covers about 50% of the island, which is located mainly in the center and eastern part of the island.  This area is not well inhabited except along the coastal area [vi].  The western side, which used to be covered by forests is now cultivated and covered in clove plantations [vii].  In the eastern side where the coral rag area is located, food crops are cultivated in small pockets where there is a thin layer of soil.  Since there is not a lot of fertile land in the coral rag area it is used mainly for grazing  [viii].     

   Zanzibar is known for its spice industry (cloves, nutmeg, cinnamon and pepper), and its beautiful beaches and rich marine life.  Zanzibar was once the leading producer of cloves, but now produces less than 10% of the world’s output.  To capitalize on its geography and climate, Zanzibar has recently been promoting tourism that has become an economic driver for the nation [viiii].  In order to attract more tourism, Zanzibar has been changing the environment in order to create a paradise setting for the tourists [viiiii].  Development tied to Zanzibar’s economic development has led to an increase in deforestation and habitat destruction.   Using geographic information systems (GIS) and remote sensing imagery, this paper examines deforestation within Zanzibar. 

Methods

  This paper focuses on Zanzibar Island, also known as Unguja Island.  There has been a main focus on the western side of the island, in particular the locations of Stone Town and Zanzibar City.  These are the cities that have the most development.  Other areas that were used in the study are Bwejuu along the eastern coast and a area along the south western coast of Zanzibar within the protected area.  These areas were studied to show that development and deforestation were increasing in areas that were not within the main commercial areas.   

    
  Global Land Cover Facility (GLCF)[i] was used to collect Landsat and elevation data.  Once on the GLCF website, Earth Science Data Interface (ESDI) was used to download images and locate Zanzibar island.  A map search on ESDI was used to locate the island.  Enhanced Thematic Mapper (ETM+) was used for Landsat data and Shuttle Radar Topography Mission (SRTM) was used for elevation data.  The clearest and most complete image of the island was identified and downloaded. 

         
   Once the image was downloaded, it was entered into the ENVI software program where the images were modified.  All of the images were subset so that only Zanzibar was clearly shown.  The elevation data was enhanced allowing a clearer image of the elevation.  A density slice was also applied to the image as well as a 3D model.   The Landsat ETM+ image was turned into an NDVI. However, since there was a lot of cloud cover over the island and there was not a better image on GLCF, this image was not used.  

         
   To get a better image of the island (one with less cloud cover), Glovis through the United States Geological Survey (USGS)[ii] was used.  Once on the Glovis website, the Zanzibar island was located. Once located, the clearest image was selected and downloaded. When the image was downloaded, it was opened with ENVI where the image was subset to focus on Zanzibar and turned into an NDVI. 

     
   The NDVI shows the vegetation of the island. In order to get a better idea of the where the vegetation was a density slice was applied to the image.   The elevation images and NDVI images were than compared to other images and maps of Zanizibar that were found online.   A simple Google image search was done to locate a comparative image.  Unfortunately there was not an image available for comparison for the elevation data.  There was a vegetation map[iii] that was found and was compared to the NDVI image.   Images from Google earth were also used as a comparison. 

    
   A time series through Google earth images was also conducted to look at the increase or decrease in vegetation on Zanzibar Island.  The information provided by Google earth covers the period 2001-2010.  The time series started in June 2001.  The images were than looked at in one-year intervals around the June or July.  The June and July images provided the clearest images with the smallest amount of cloud cover.   Since there was a lot of cloud cover, an area in the southern western part of Zanzibar and an area in the northern western part of Zanzibar were put under a time series through Google earth and compared to the images from Glovis and GLCF.

Results

  The following Goggle satellite images taken between January 29, 2001, and June 21, 2010, document decreasing vegetation on the Island of Zanzibar over the past nine years.  Progressive deforestation is particularly noticeable on the western side of the island where trees have been harvested for building and a cottage industry exists to supply firewood and charcoal to urban areas along the coast.  Agriculture remains the primary industry in Zanzibar, and expanding cultivation of the island has resulted in further loss of forest lands.

  
  A majority of forests and vegetation are located in the western side of the island.  Because of cloud cover, it is harder to track vegetation in the middle of the island.  Forests located in the middle of the island include the Kiwengwa Pongwe Forest, Kichwele Forest Reserve, Muyuni Forest, and the Jozani Chwaka Bay National Park (including the Jozani Forest).  

Google Earth Image: June 29, 2001

Google Earth Image: June 21, 2002

Google Earth Image: April 16, 2003

Google Earth Image: July 4, 2004

Google Earth Image: September 2, 2005

Google Earth Image: June 12, 2006

Google Earth Image: June 23, 2007

Google Earth Image: October 21, 2008

Google Earth Image: June 29, 2009

Google Earth Image: June 21, 2010

  The following images are of Zanzibar city and Stone Town.  These are the largest urban areas on Zanzibar and contributes to the most deforestation on the island.

Google Earth Image: 2010 - Zanzibar City and Stone Town (zoomed out)

Google Earth Image: 2010 - closer view of Zanzibar city and Stone Town

  Also impacted are coastal areas where tourism is a growing industry.  Deforestation and increased use of concrete has led to higher temperatures and lower rainfall, leading to desertification.  The image below is of Bwejuu, a developing resort region on the island.

Google Earth Image: September 2, 2005

This image was taken off of the eastern coast of the island.

Google Earth Image: October 16, 2007

Within two years vegetation has noticeably decreased.  The border of Bwejuu has moved more inland and the white spot east of Bwejuu has increased, almost doubling in size. 

Google Earth Image: November 1, 2005

This image was taken off of the Southern Western Coast of Zanzibar.

Google Earth Image: June 18, 2009

The landscape of the area changed dramatically.  There is now a fairly developed town along the coast.  Also the areas from the 2005 image where vegetation was low or not present is now green and almost non-existent.  It should be noted that this area is within a protected area of Zanzibar.

Map off of Google Search: Shows vegetation on the island

This map shows that most of the vegetation is located on the western part of the island.  

This is an NDVI image taken from Glovis USGS (a density slice from ENVI was applied to the image)

This image confirms that most of the vegetation is located on the western part of the island. The color red represents the areas with heaviest vegetation.  The area outlined in black is a rough sketch of the protected area in Zanzibar according to the Glovis USGS data.

Image provided from an article from Myers. Please see references for article details.

This map outlines the fertile and urban areas on Zanzibar Island.  When compared to the NDVI image and Vegetation map above, the fertile area is the area with the most vegetation.  It is also the area with the highest population concentration.   

Image A

Image B

Image C

  The images above provide topographical data.  All of the images are from the Global Land Cover Facility using SRTM data.  Image A was enhanced after being put into ENVI.  The lightest areas represent the highest elevations and the darkest areas represent the lowest elevations.  Images B and C had a Density slice applied to them. Image C is a 3D model of image B.  In images B and C, the light blue areas represent an elevation of 75 meters or more above sea level. 

The island is generally flat.  The majority of the vegetation is located on the western part of the island which is also the area of highest elevation.  The high elevation may prevent cultivation in that area, limiting agriculture to a smaller area.  This may be the reason most of the urbanization is in the southern part of the fertile land (as seen in the map before the elevation data) and may possibly be one of the reasons why urbanization has expanded in the eastern coast.   

Discussion

  There is little scientific research done on Zanzibar’s vegetation.  A majority of the information on Zanzibar deals with tourism or endangered animals on the island.  The information that I was able to find on the vegetation in Zanzibar was culled from books or articles that focused mainly on tourism. 

   While looking for satellite images of the island, it was very difficult to find a clear image.  A lot of the images had cloud cover, which made it difficult to do an analysis of the island.  The images with the smallest amount of cloud cover were used, but even those images were hard to fully analyze.  Since there is little scientific information available on the island, there were few detailed maps of the island that could be used as comparisons to the images I used. 

  With that said, further research on vegetation should be done on the island.  Zanzibar is an agriculturally based country with a majority of the agriculture taking place in the fertile region.  This is adding to the deforestation.  Since tourism is a growing industry in Zanzibar, there is further development on the island to accommodate the tourists. This has lead to landscape reconstruction, such as new beach resorts, to attract tourists to a “paradise” location.  If deforestation continues the fertile land may be destroyed.  When further research is conducted than field study is necessary.  Since the satellite images are unclear, field study should be conducted to measure the vegetation in Zanzibar.  It would be ideal, if a 10-year field research study were conducted measuring the forest and vegetation boundaries along with the growth of agriculture and urbanization.  I would also use aerial photography to capture the vegetation and urbanization areas of Zanzibar.  If aerial photographs were taken over a period of time than the images can be compared and the vegetation and urbanization boundaries can be analyzed.  Aerial photography along with field research will provide more solid information on Zanzibar's vegetation.

Reference

Abstract:

[i] Chachage, Chachage Seithy L. (2000) “Environment, Aid and Politics in Zanzibar” DUP, 15-16.

[ii] Gossling, Stefan (2002) “Human-Environmental Relations With Tourism” Elsevier Science, 2, 539-556.

Introduction:

[i] May, 1997.  www.Zanzibar.net

[ii] ibid

[iii] Chachage, Chachage Seithy L. (2000) “Environment, Aid and Politics in Zanzibar” DUP, 15-16.

[iv] Shelswell-White, G.H. (1952) “Guide to Zanzibar” The Government Printer, 10.

[v] Chachage, Chachage Seithy L. (2000) “Environment, Aid and Politics in Zanzibar” DUP, 15-16.

   

[vi] ibid

[vii] ibid

[viii] ibid

[viiii]  November, 2010 “Zanzibar” Wikipedia. http://en.wikipedia.org/wiki/Zanzibar#Culture_and_language

[viiiii] Gossling, Stefan (2002) “Human-Environmental Relations With Tourism” Elsevier Science, 2, 539-556.

Methods:

[i] http://www.glcf.umd.edu/index.shtml

[ii]  http://glovis.usgs.gov/

[iii] http://www.kalerta.com/media/zanzibar/zanzibar_map-back-small.jpg

Results:

Image:

[i] Myers, Garth Andrew (2002) “Local communities and the new environmental planning: a case study from Zanzibar” Royal Geographical Society, 34.2, 149-159.