Nicola Arndt und Matthias Pohl - Neobiota

To identify specific alternatives and constraints in the development of a global EZ map appropriate for
FRA 2000 purposes, FAO conducted two preliminary studies (ZHU 1997, PRETO 1998). Findings from
these studies, experience in the development of the tropical EZ map for FRA 1990, and
recommendations from other parties consulted in the process indicated that the development of an
entirely new global ecological zoning map by FAO could not be completed by the year 2000, due to
time constraints and the large amount of scientific, organisational and financial resources required.
With this in mind, follow-up investigation focused on identifying an existing scheme that might be
used or adapted to FAO’s needs.
Due to the enormity of conducting the work on a global scale, the most appropriate classification
scheme had to meet FAO’s thematic requirements, be practical to construct with available resource
and meet the scrutiny of a diverse group of users from all parts of the world. A survey of existing
schemes revealed several possibilities. Each of the existing schemes were developed for specific
purposes according to various environmental criteria, with macroclimate as an element being used by
most (PRETO 1998, WCMC 1992). This is logical, as the macroclimate, that is temperature and
precipitation, correlates well with the potential natural vegetation associated with a particular locale. In
this respect, macroclimate was considered a logical basis for the FRA ecological zoning as well.
For the choice of climatic parameters to be used in the FRA 2000 map a number of global systems
were surveyed including KÖPPEN (1936) modified by TREWARTHA (1968), THORNTHWAITE (1933),
and HOLDRIDGE (1947). Out of these possibilities, initial work indicated by Köppen-Trewartha was a
good candidate for the FRA 2000 work due to the number of classes that corresponded well to FRA
2000 needs. Moreover, further study showed that while Köppen-Trewartha is based on climate there is
a demonstrated good correspondence between its subzones or climatic types and the natural climax
vegetation types and soils within them (BAILEY 1996) 3 . These factors were seen as major advantages
in favour of using the Köppen-Trewartha system for the backbone of the FRA 2000 zoning.
One good precedent for using Köppen in global ecological zoning was carried out by Robert Bailey,
who used the Köppen-Trewartha system in toto for development of his ecoregion scheme for North
America and the rest of the world (BAILEY 1989, 1996, 1998). He noted that although ecological
zones can be mapped by reference to a single feature (such as climate), they must always be checked
to ensure that the boundaries have ecological significance. At the same time, a climatic map showing
such key features as temperature and precipitation is not necessarily an ecological map until the
boundaries are shown to correspond to significant biological boundaries. Likewise maps of landform
types (derived from digital elevation data) are not necessary ecological maps until it has been shown
that the types co-vary with other components of the ecosystem, such as vegetation (BAILEY, personal
communication 1998).
To further the development of the work, FAO in cooperation with EDC and WCMC developed a
prototype zoning scheme for FRA 2000 based on Köppen-Trewartha. The zoning was made
hierarchical using Köppen-Trewartha’s climatic groups and types as FAO Ecological Zone levels 1
and 2. A third level was also tested during the pilot project and represents the differentiation within the
first two levels according to landform. Mountains with altitudinal zonation were distinguished from
lowland plains (see Table 1).
3 This is largely because Köppen derived his climate classes from observations on the distribution of natural
vegetation types on various continents (KÖPPEN 1931).
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