ORIGINAL PAPER
The classification of wetlands: integration of top-down
and bottom-up approaches and their significance
for ecosystem service determination
Erwin J. J. Sieben
.
Skhumbuzo P. Khubeka
.
Simangele Sithole
.
Nancy M. Job
.
Donovan C. Kotze
Received: 30 January 2017 / Accepted: 23 November 2017 / Published online: 30 November 2017
Ó Springer Science+Business Media B.V., part of Springer Nature 2017
Abstract The typology of wetlands provides
important information for both water resource man-
agers and conservation planners. One of the most
important aims of allocating wetlands to a certain type
or class is to provide information about the ecosystem
services that the wetland provides. There are two main
approaches towards wetland classification. Firstly,
there are top-down approaches whereby wetlands are
divided into several categories based on a conceptual
understanding of how the wetland functions (mostly
with regards to water flows). Secondly there are
bottom-up approaches whereby the classification of
wetlands is based on the collection of data in the
wetland that is then subjected to various clustering
techniques (mostly with regards to biodiversity). The
most utilized system of top-down classification
assigns wetlands into hydrogeomorphic units, which
function as a single unit in terms of hydrology and
geomorphology. This type of classification is most
useful for water resource planning, as it provides
information about how the wetland is connected to the
drainage network and what are the water inflows,
throughflows and outflows of the wetland. The
bottom-up classification approach typically focusses
on the classification of wetland habitats rather than
complete wetlands, where wetland habitat represents a
spatial unit delineated on the basis of vegetation,
embedded within the (complete) hydrogeomorphic
unit, and defined as an area of wetland that is
homogeneous in terms of opportunities for plant
growth. At a broad scale, most ecosystem services
can be superficially derived from the hydrogeomor-
phic unit type and the way water moves through a
wetland, but habitat units and the plant species that
define them would have a specific effect on the
delivery of ecosystem services, for example, with
different assemblages providing different resistance to
flow. Some types of ecosystem services are exclu-
sively linked to specific wetland habitats, especially
provisioning services. For this reason, it is proposed
that a combined approach of hydrogeomorphic clas-
sification together with a vegetation map, offers the
maximum information value for ecosystem service
determination. In order to account for the potential
pitfall of ‘‘double counting’’ when combining the top-
down and bottom-up approaches, each service needs
to be considered individually with reference to the
degree to which a service is either: (a) primarily
determined by HGM class/attributes and modified by
E. J. J. Sieben (&) Á D. C. Kotze
University of KwaZulu-Natal, College of Agriculture,
Engineering and Science, Westville, KwaZulu-Natal,
South Africa
e-mail: siebene@ukzn.ac.za
S. P. Khubeka Á S. Sithole
Ezemvelo KZN Wildlife, Pietermaritzburg,
KwaZulu-Natal, South Africa
N. M. Job
University of the Free State, Institute for Groundwater
Studies, Bloemfontein, Free State, South Africa
123
Wetlands Ecol Manage (2018) 26:441–458
https://doi.org/10.1007/s11273-017-9585-4
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