The Full Picture

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Bridging scaling gaps for the

assessment of biodiversity from space

Michael E. Schaepman, Centre for Geo-Information, Wageningen University and Alterra;

Zbynek Malenovský and Lammert Kooistra, Centre for Geo-Information, Wageningen University;

C.A. (Sander) Mücher, Centre for Geo-Information, Alterra;

Wilfried Thuiller, Université J. Fourier, Laboratoire d’Ecologie Alpine

arious definitions of biodiversity exist, but a common

denominator of these is always a certain scale dependency.

The United Nations (UN) Convention on Biological

Diversity defines biodiversity as: ‘the variability among living

organisms from all sources, including, “inter alia”, terrestrial,

marine, and other aquatic ecosystems, and the ecological

complexes of which they are part: this includes diversity within

species, between species and of ecosystems’.

Scales in biodiversity are relevant and need to be addressed individu-

ally. Biodiversity is often plotted as taxonomic richness of a geographic

area, occasionally referenced to a temporal scale. This, along with the

uneven distribution of biodiversity on Earth, renders biodiversity

measurements using spatially explicit methods particularly complex.

Lately, biodiversity is assessed increasingly using air- and space-borne

Earth observation instruments. However, ecologists

mainly value biodiversity in terms of species richness, as

well as using various indices, whereas Earth observation

based instruments usually measure the spatial distribu-

tion of radiance fields, backscattering and polarization

state changes.

It is the main challenge of Earth observation and

ecology to establish semantic interoperability between

these two fields, and then develop common sampling

schemes and bridge scaling gaps. This would finally allow

a spatio-temporal continuous sampling of biodiversity

with limited discontinuities. In combination with solid

and continuous ground observations, long-term perspec-

tives of various scale biodiversity assessments are

emerging. These perspectives recieve strong support from

networks including the Global Earth Observation System

of Systems (GEOSS) Biodiversity Observation Network,

the US National Ecological Observatory Network

(NEON) and AlterNet (a network of excellence aiming

to build lasting integration of biodiversity research).

There are two particular scaling-based approaches for

the assessment of biodiversity at continental and regional

scale

within

this

context.

combined

disaggregation/aggregation scheme is used to derive domi-

nant species abundances at large spatial resolution

(typically 500 to 1,000 m pixel size) for continental scale

applications. The other, a regional scale (0.5 – 5 m spatial

resolution), is used to assess floristic diversity, canopy

biochemistry and structure. Both approaches have been

proven to deliver relevant results for the assessment of

biodiversity from space, as well as bridging scaling gaps

previously unexplored.

Necessity to observe biodiversity changes

The latest trends of the global climate are, unfortunately,

weakening the biodiversity-ecosystem bound. Ecosystem

biodiversity is strongly related to actual ecosystem

services and goods delivered, and affected by natural and

human-induced environmental processes. Increasing

temperatures are relocating ecosystems on the Earth, and

further re-emphasizing the uneven biodiversity spatial

distribution. Consequently animal and plant species are

Floristic diversity in a sub-alpine meadow

Photo: Zbyn

k Malenovský, Col du Lautaret, France

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IODIVERSITY