Grassroots Grassroots - Vol 20 No 1 | Page 4

FEATURE
Is gully expansion a major
issue for key biodiversity
values in arid lands?
Hugh Pringle
Current Address: Ecosystem Management Understanding (EMU) ™
E-mail Address: emulandrecovery.org.au
C
ontext: My EMU colleagues and I
have attended major regional bio-
diversity conservation workshops
in Outback Australia aimed at identify-
ing priority threats. When we raised the
issue of expanding gully erosion and
landscape droughting, it has been ex-
plained to us that gullies are more rele-
vant to agricultural contexts (sheep and
cattle stations). “Soil erosion is caused
by overgrazing on cattle stations; that
is not what we are talking about at this
biodiversity workshop”. The implied
belief is that the management of the
physical environment is not part of bio-
diversity conservation and perhaps that
biodiversity conservation is not impor-
tant on grazed lands? It is almost as if
the biological interactions occur in the
clouds regardless of landscape succes-
sion processes (Figure 1).
The importance of natural hydrologi-
cal regimes to their habitats: Natu-
ral creeks usually start in uplands and
spread out as they meet flatter land,
distributing channel flow into fingers
and sheet flow as fertile floodout fans
(Schumm, 1977). Gullies generally form
and grow wherever the land has been
cut and “waterfalls” are developed that
then cut back in the direction of strong-
est flow (Figure 2)(Pringle et al., 2011).
Natural creeks generally develop in
steep country where small flows come
together and gain energy (tributary pat-
tern) and then rapidly lose energy on
meeting flatter land and tend towards
distributary flow. That flow then ends up
gently soaking floodplains below (Fig-
ure 3). This natural pattern of tributary,
then distributary flow and then bottom-
lands has local wetlands from the top of
the catchment (e.g. local grassy drain-
age depressions) down to the flood-
plains with major swamps.
The different wetland “jewels in the
crown” support a different suite of
species to their wider landscape and
have evolved together in an evolu-
tionary partnership. Wetlands – be
they small pans or large floodouts,
03
Figure 1: Biological interactions occurring in the clouds. Physical landscape form,
function and trend are too often ignored! (Drawing by Ken and Lynne Tinley ©)
swamps and floodplains - dry out last
and are critical drought buffering habi-
tats (McNaughton, 1983; Stafford Smith
& Morton, 1990; Morton et al., 1995;
Duguid et al., 2005; Fynn & Bonyongo,
2011; Morton et al., 2011). They are bio-
logically distinctive and most vulnerable
to livestock pressures as seasons de-
cline.
Can these critical drought buffering
areas and the broader landscape real-
istically be understood bio-centrically
as suggested in some text books on
ecology (Krebs, 2009) or do we need
to return to a more holistic ecology in
this specific regard (Cowles, 1901; Cle-
ments, 1916; Cole, 1963; Tinley, 1982)?
Can earth sciences complement biolog-
ical approaches in understanding land-
scape behaviour (Pulley et al., 2018)?
Should key biodiversity values be man-
aged wherever they occur (Kain, 2008)?
Has contemporary bio-centricity been
adequate? The Wetlands Indaba in
Kimberley, South Africa last year (2018)
was exceptional in the attention paid to
physical earth processes. Professor Fred
Ellery epitomised a wide-eyed view of
landscapes (Pulley et al., 2018) and his
students will benefit from this holism.
He presented the idea that gully erosion
could create wetlands in the specific
contexts, which makes sense and begs
different thinking in planning restora-
tion. Should all gullies be “healed” or
are at least some of them part of a long-
term geological succession that created
for instance upland valley floors with
wetland systems? One might pragmati-
cally err on the side of stabilising gully
systems given that contemporary land
use pressures are at least exacerbating,
if not initiating landscape incision (Mab-
butt et al., 1963; Cooke & Reeves, 1976;
Fanning, 1994; Pringle et al., 2011).
Grassroots
Vol 20
No 1
March 2020