Environmental Engineering Reference
In-Depth Information
Elk
Godwit
Harrier
Otter
Fig. 1.3
Spatial consequences of four alternative restoration targets. Scenario Elk refers to restoring a wilderness,
scenario Harrier to an arcadian landscape, scenario Godwit to a functional landscape with multiple users, and
scenario Otter is a mix of the above with emphasis on improving the connectivity between landscape elements
(after Harms
et al
. 1993). With kind permission of Springer Science and Business Media.
whether these estimates are correct or not, this means
that only one-eighth of all living species has actually
been described. It implies that our knowledge of bio-
diversity is pretty limited and therefore difficult to use
as a yardstick.
In practice this problem is generally solved by
choosing
certain target or indicator organisms that are
used to measure (changes in) biodiversity in a given
area. This can lead, however, to unwanted (and un-
foreseen) conflicts. Restored areas are often colonized
very quickly by mobile animals like birds whereas less-
mobile organisms like plants or certain insect groups
may (re-)appear much more slowly. If bird species rich-
ness is taken as a criterion such a project is regarded
as very successful, whereas the project might be much
less successful in terms of vegetation development.
A second point of attention is to use the concept
of biodiversity in a sound way in restoration projects
and always to compare the actual situation to a well-
chosen reference situation. Species-rich but otherwise
disturbed communities will be valued much more
highly than certain species-poor targets such as bogs,
heathlands or tundras. Even then, intermediate stages
might be more species-rich than the actual restora-
tion goal and this implies that elements of valuation
come into play. If we examine the species-density/
