Mapping decadal land cover changes in northern Namibia using the - - PowerPoint PPT Presentation

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Mapping decadal land cover changes in northern Namibia using the - - PowerPoint PPT Presentation

Sep 17, 2023 934 likes •1.11k views

Mapping decadal land cover changes in northern Namibia using the Landsat satellite archive (1975-2015) Physical Geography and Environmental change University of Basel Vladimir Wingate , vladimir.wingate@unibas.ch V. R. Wingate 2014 Outline

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Mapping decadal land cover changes in northern Namibia using the Landsat satellite archive (1975-2015)

Physical Geography and Environmental change University of Basel Vladimir Wingate , vladimir.wingate@unibas.ch

  • V. R. Wingate

2014

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Outline

  • IntroducQon

– Study site and vegetaQon cover change in N Namibia – Landsat satellite data

  • ObjecQves

– Assess the extent of vegetaQon cover change – i.e. deforestaQon, vegetaQon gain

  • Method

– VegetaQon change mapping using the whole Landsat satellite archive – Landsat satellite image analysis tools

  • IniQal results

– MulQ-temporal land cover class maps of vegetaQon cover change – Data on extent of loss and gain of forest cover

  • Next steps

– Mapping fracQonal/percentage vegetaQon cover

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Study site

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northern Namibia

  • VegetaQon change

– Human impact – Reduced savannah woodland – Expansion of arable land – Increased grazing

  • Expand on change work

– Erkkilä et al. (2001) – Röder et al. (2014)

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Landsat data

  • Landsat archive

– Freely available, USGS – Local, regional, and global-scale analysis – VegetaQon change i.e. deforestaQon – Numerous applicaQons – 1972 – Present – RepeQQve, synopQc – High resoluQon (30x30m pixel)

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ObjecQve

  • Map changes in land cover in N Namibia

– Between 1975 and 2014 at decadal intervals – Emphasis on woodland/savannah cover change – Arable/agricultural land expansion

  • V. R. Wingate

2014

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Methods

  • Post-ClassificaQon method

– Land cover is assigned to a class – Easily measure extent (i.e. ha, km2) – TransiQons between classes

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Landsat archive analysis

  • Whole archive available for analysis:

– Google’s earth engine – Select the best quality pixels for given period – Create a new best image – Classify new images into land cover classes for change analysis

hfps://earthengine.google.com

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IniQal results

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IniQal results

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Results and discussion

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Results and discussion

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Results and discussion

  • Land cover change between 1975-2014

– Over all decrease in woodland – Increase in arable land – Variable rates of change – Losses and gains – Small-scale conversion

  • V. R. Wingate

2014

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LimitaQons and further work

  • LimiaQons of post-classificaQon method

– Difficult to produce consistent results – SubjecQvity introduced – operator judgements – Leads to erros – hard to replicate

  • Savannahs environments

– Heterogenous land covers – Inter-intro annual variaQon – Shihs – fire, rainfall, grazing

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FracQonal cover

  • QuanQtaQve analysis of the percentage cover

(0-100%) of live vegetaQon, dry vegetaQon and exposed substrate for each satellite pixel

– ecologically meaningful maps – idenQfy % forest cover – deforestaQon

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Conclusion

  • Decrease in vegetaQon cover
  • Increase in arable land
  • Number of limitaQons with mapping methods
  • Especially true for savannahs environments
  • Probably resulQng in the variable results
  • bserved
  • Next pat of the study will explore the issue

further using FracQonal Cover method