MODIS VCF should not be used to detect discontinuities in tree cover due to binning bias. A comment on Hanan et al. (2014) and Staver and Hansen (2015)

Gerard, France; Hooftman, Danny; van Langevelde, Frank; Veenendaal, Elmar; White, Steven M.; Lloyd, Jon. 2017 MODIS VCF should not be used to detect discontinuities in tree cover due to binning bias. A comment on Hanan et al. (2014) and Staver and Hansen (2015). Global Ecology and Biogeography, 26 (7). 854-859. https://doi.org/10.1111/geb.12592

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Official URL: http://dx.doi.org/10.1111/geb.12592

Abstract/Summary

In their recent paper, Staver and Hansen (Global Ecology and Biogeography, 2015, 24, 985-987) refute the case made by Hanan et al. (Global Ecology and Biogeography, 2014, 23, 259–263) that the use of classification and regression trees (CARTs) to predict tree cover from remotely sensed imagery (MODIS VCF) inherently introduces biases, thus making the resulting tree cover unsuitable for showing alternative stable states through tree cover frequency distribution analyses. We here provide a new and equally fundamental argument why the published frequency distributions should not be used for such purposes. We show that the practice of pre-average binning of tree cover values used to derive cover values to train the CART model will also introduce errors in the frequency distributions of the final product. We demonstrate that the frequency minima found at tree covers 8 % to 18 %; 33 % to 45 %; and 55 % to 75 % can be attributed to numerical biases introduced when training samples are derived from landscapes containing asymmetric tree cover distributions and/or a tree cover gradient. So it is highly likely that the CART, used to produce MODIS VCF, delivers tree cover frequency distributions that do not reflect the real world situation.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1111/geb.12592
UKCEH and CEH Sections/Science Areas:	UKCEH Fellows Pywell Reynard
ISSN:	1466-822X
Additional Keywords:	alternative stable states, frequency distribution, forest, MODIS VCF, remote sensing, savannah, tree cover
NORA Subject Terms:	Ecology and Environment
Date made live:	25 May 2017 13:59 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/516002

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1111/geb.12592

UKCEH and CEH Sections/Science Areas:

UKCEH Fellows
Pywell
Reynard

ISSN:

1466-822X

Additional Keywords:

alternative stable states, frequency distribution, forest, MODIS VCF, remote sensing, savannah, tree cover

NORA Subject Terms:

Ecology and Environment