Download factors that influence the “carrying capacity” of game species

29
FACTORS THAT INFLUENCE THE “CARRYING CAPACITY” OF GAME SPECIES
V. Gulca1, P. Angelstam2, R.H. Barrett3
1
National Academy of Science of Belarus, Centre for Bioresources, Minsk, Republic of Belarus, [email protected]
2
Swedish University of Agricultural Sciences, School for Forest Management, Skinnskatteberg, Sweden,
[email protected]
3
University of California, Department of Environment Science, Policy and Management, Berkeley, CA, USA,
[email protected]
Introduction
The term carrying capacity was
coined by Aldo Leopold (1933:50-51)
in his work “Game management”, and
is one of the most common concepts
in wildlife management (Caughley &
Sinclair 1994). However, the interpretation of this concept and its application in practical management varies.
For example, while Morrison 2000:46
argued that ”... while carrying capacity
may be equated with a certain level of
habitat quality, the quality itself should
be based not on the number of organisms but on the demographics of individual populations.” From other parts
of the world scholars have argued that
the “concept of carrying capacity is the
cornerstone for sustainable game
management, because it brings clarity
to many questions in the theory and
practice of wildlife management” (Юргенсон 1969 quoted by Львов 1984).
Although, according to Almasan
(1988), rankings of carrying capacity
for hunting land management units
were elaborated only in former socialist countries, the term covers a variety
of meanings, and unless we a careful
and define the term, we may merely
cause confusion (Caughley & Sinclair
1994, Львов 1984).
For example, apart from density or
demographics of the focal game species of interest to hunters, estimates of
carrying capacity also depend on the
consequences of a particular game
species composition and density for
other aspects of ecosystems. For example, large herbivore populations
causing acceptable damage to less
preferred tree species (e.g., Scots
pine) of importance to boreal forestry
may still cause severe damage to
more preferred tree species (e.g., aspen) of importance for forest biodiversity conservation (Angelstam et al.
2000). It is thus possible to identify
management contexts professional
wildlife management and conservation
(public land in the US), opposing
stakeholder views and unresolved conflict (Sweden) and with evident crisis in
wildlife management and conservation
(Moldova).
Un-reflected consideration to carrying capacity issues is not a guarantee
to succeed in wildlife and habitat conservation. First, we list reasons why it is
important to estimate carrying capacity. Second, we identify what factors influence carrying capacity and how it is perceived among stakeholders. Finally, we discuss the need to include both target species, the ecosystem in
which it lives and different stakeholders views to define different levels of
carrying capacity.
Why it is important to estimate carrying capacity
According to Caughley & Sinclair (1994) ecological carrying capacity is
the natural limit of a population set by resources in a particular environment.
This equals the mean maximum number or biomass of organisms of a given
species that can be sustained or survive on a long-term basis within an ecosystem (Helms, 1998). According to Negrutiu (1983) the term that expresses
the conditions offered by given hunting land management unit for one hunting species is called carrying capacity. However, using large herbivores as
an example, other stakeholders may focus on the state of its predators, the
herbivores’ food species or other effects of herbivores as vectors of disease.
What carrying capacity is varies thus among stakeholders with different focus.
To evaluate feasible management options for different stakeholders, including to solve management problems such as reducing the impact of increased browsing by wild herbivores; increasing wildlife populations quality;
increasing number of wildlife individuals; anticipating conflicts; identifying,
controlling and removing limiting factors; balancing of agricultural, forestry,
and wildlife management interests; renting of hunting grounds; accurate estimates a systems analysis approach is needed. Given this complexity, while
carrying capacity remains an important topic, it is ambiguous, and all relevant variables are rarely taken into account in management and modeling of
populations, ecosystems and landscapes (Morris & Mukherjee 2007, Angelstam et al. 2000).
What factors influence carrying capacity?
A principle developed in agricultural science by Carl Sprengel (1828) and
later popularized by Justus von Liebig, states that population growth is controlled not by the total amount of resources available, but by the scarcest resource (the limiting factor). Shelford’s Law of Tolerance holds that first the
presence and then the success of an organism depend on the completeness
of a complex of conditions. More precisely, each organism – whether the individual or the species population – is subject to an ecological minimum,
maximum, and optimum for any specific environmental factor or complex of
factors linked to a particular aspect of the coupled human and nature system, or landscape.
Discussion
Because the concept of carrying capacity is relative to particular elements of landscapes and how they are used, and not stipulated in any law,
both ecological and social systems need to be studied. Research about carrying capacity thus encompasses a wide range of questions. What are different stakeholders’ views on the balance between game populations and
other parts of ecosystems? What is the effect on population density, demography, health and trophy quality of different views on carrying capacity?
What is the power of different stakeholders?
30
REFERENCES
bridge: Blackwell Scientific Publications, 1994. - 336 p.
Helms J.A. The dictionary of forestry. – Bethesda: The Society of American
Foresters, 1998. – 210 p. .
Almasan H. Bonitatea fondurilor de
vinatoare si efectivele optime la
principalele specii de vinat din
Romania. – Bucuresti: Redactia de
Propaganda Tehnica Agricola, 1988.
– 116 p.
Leopold A. Game management. -Wisconsin: The University of Wisconsin
Press, 1933 (1986). - 482 p.
Angelstam, P., Wikberg, P. E, Danilov,
P, Faber, W. E. Nygrén, K. Effects of
moose density on timber quality and
biodiversity restoration in Sweden,
Finland and Russian Karelia // Alces. - 2000. Vol. 36:133-145.
Morrison M. Wildlife restoration. Techniques for habitat analysis and animal
monitoring. -Washington: Island Press, 2002. - 212 p.
Caughley G., Sinclair A.,R.,E. Wildlife
ecology and management. – Cam-
Morris D.W. & Mukherjee S. Can we measure carrying capacity with foraging
behavior // Ecology. – 2007. Vol. 88. – P. 597-604
http://www.esajournals.org/doi/abs/10.1890/06-0389?journalCode=ecol
Negrutiu A. Vinatoare si salmonicultura. – Bucuresti: Editura didactica si
pedagogica, 1983. – 343 p.
Львов И. А. Дикая природа: грани управления. Очерки биотехнии. М. :
Мысль, 1984. 191 с.