Ecosystems and Ecology
Ecosystems and Ecology
Author: Prof Koos Bothma
Licensed under a Creative Commons Attribution license.
SUMMARY AND CONCLUSIONS
Ecology is an old science and its principles are essential to human survival. Yet they are still being largely
ignored despite being the basis for the development of a One Health approach which will ensure healthy
animals and people that live in an optimal environment. Ecological processes operate on an intricate web
of energy cycling. An ecosystem is a functional environmental unit that consists of a diversity of biological
organisms that interact with an ever-changing abiotic environment. The One Health concept aims at
harvesting the benefits of healthy ecosystems optimally by limiting harmful environmental disturbances.
The ultimate objective is to produce an optimal environment for sustainable human development.
Ecosystems are the products of ecological succession that has occurred over millennia in a specific
physical environment to create intricate food-web matrices. In these matrices solar energy is received and
converted to biological energy that is harnessed and used by producers and consumers. Ultimately
decomposers break down organic waste to recycle the energy for a limited time. Humans are recent
additions to these food-webs but their actions are greatly harmful to ecosystem survival and the
ecological processes upon which their maintenance depend.
From a case study of the relatively simple south-western Kalahari ecosystem in South Africa it is clear
that some of these ecological processes are delicate and easily disturbed. Moreover, some of them have
thresholds that create irreversible ecological harm when they are exceeded by continual overutilization.
Novel ecosystems can develop from time to time and the world is currently facing the consequences of
some of them that have developed in response to the rampant mis-use of the renewable natural
resources. Major forces in this regard are factors such as deforestation, soil erosion, and overgrazing and
global climate change. Invasive animals and plants are also a serious threat. As humans degrade existing
ecosystems, novel ecosystems emerge increasingly and may even threaten human survival. Genomic
studies may help to counter this threat because they provide a vital key to understanding how complex
natural ecosystems are being formed and maintained.
The more mature an ecosystem becomes the more interrelated food-web matrices it contains. Tropical
terrestrial ecosystems are almost totally maintained by the recycling of nutrients and once lost cannot be
replaced. Temperate terrestrial ecosystems have a greater resilience to change although they have lower
levels of primary productivity than the more equatorial ones. The lowest production of biomass occurs in
the Polar Regions. Herbivores and apex carnivores play a vital part in ecosystem development and
maintenance and their removal will lead to cascading effects along the ecotonal boundaries between two
1|Page
Ecosystems and Ecology
major ecosystems. However, some organisms require complete ecosystems for their survival and cannot
make use of edge-effects in ecotonal zones.
As did this lion Panthera leo at Grootbrak in January 1978 in the Kgalagadi Transfrontier Park of the southwestern Kalahari ecosystem, lions climb trees well but refrain from doing so unless they are being harassed
by a pack of spotted hyaenas Crocuta crocuta or by humans
The maintenance of a natural biodiversity is vital to ecosystem health and management. Nevertheless,
the Earth has already survived five major extinction periods when a large proportion of its life became
extinct. Humans are currently driving a sixth extinction event and unless they pay heed to the ecological
lessons of the past may well be among those organisms that could soon disappear. A switch to a One
Health approach could avert this disaster but it has major social, economical and political ramifications.
Rampant new epidemics are already a “symptom” of ecological boundaries that should rather remain
untested.
One of the largest threats to ecosystem health is the fragmentation of habitats and ecosystems. Among
others it has already lead to disturbances in gene flow and survival capacity in some ecosystem
components. It is therefore important to develop land management strategies in which matrix habitats are
being maintained along with viable passage ways between fragmented patches. Many transfrontier parks
are designed to introduce at least such corridors or passages if they cannot become large contiguous
conservation areas. This matrix approach will allow species to disperse. Such dispersal will depend on
2|Page
Ecosystems and Ecology
the functional abilities of the organism that is involved, including its dispersal ability and niche breadth. It
will also depend on abiotic site characteristics which may vary in space and time.
On a geographical scale of biodiversity, regions of high endemism become important. A fundamental land
management guideline is to maintain productive ecosystems that capture energy and support food-webs,
whether local or regional. The identification and allocation of management resources to land management
units where losses in biodiversity have not yet occurred should therefore be a priority.
Species-level conservation should not only be limited to globally rare or threatened species because the
conservation status of the more common species can change rapidly. Some currently common species in
the world may come under threat of future population decline because of human-induced changes in
ecosystem dynamics. In addition, continual habitat degradation will lead to species extinction cascades.
Such degradation is often the result of overexploitation of the renewable natural resources of the world.
Even the deliberate extinction of parasites and their vectors such as the tsetse fly can and have serious
implications on ecosystem dynamics because it may involve the decimation of large tracts of contiguous
woodland that serve as habitat for a multitude of wildlife species. The scale of biodiversity reduction
determines how critical the changes will be to ecosystem functioning. The ultimate solution lies in
understanding the complexity of ecosystem management.
Small, burrowing animals play a major role in soil quality and are vital to maintaining ecosystem
functioning because they are part of the many mutualistic associations between organisms. Friable,
healthy soils underpin healthy vegetation without which ecosystems cannot function optimally. Crop
production practices are largely detrimental to soil formation and with deforestation it has already
contributed to the rise and fall of ancient civilizations such as that of the Khmer in Cambodia and the
Maya in tropical Central and South America.
Large herbivores are the first major mammal trophic level in terrestrial ecosystems. As in marine
ecosystems, optimal herbivory has an important regulatory role in ecosystem functioning. Herbivory is
responsible for important ecological cascades throughout terrestrial and marine ecosystems. Large
ungulates consistently depress the densities and primary productivity of trees in the African savannas,
and with them that of a host of related organisms. However, complex interactions through herbivory in
ecosystems make predictions of their general effect problematic. Ecosystems with a low primary
productivity are especially susceptible to human-induced modification. The introduction of exotic
herbivores such as West Zambian sable antelope Hippotragus niger, Malawi roan antelope Hippotragus
equinus, fallow deer Dama dama, black-faced impala Aepyceros melampus petsersi, dik-dik Madoqua
kirkii and many more into South Africa for purely economic reasons is one of South Africa’s current
anthropogenic problems. The same type of problem is being faced elsewhere in southern Africa and
globally. A priority is the use of techniques to set animal stocking densities that are in line with the quality
and quantity of the vegetation in a given ecosystem.
3|Page
Ecosystems and Ecology
Water quantity and quality are usually overlooked totally and yet water and food will determine the
sustainability of humans on the Earth in the near future. Moreover, the presence of enough water of good
quality has a ripple effect through ecosystems. Suitable risk assessments must not only be developed for
all ecosystems but must be applied diligently throughout the world.
The decomposition of organic waste depends on the type of ecosystem and the related principles should
form part of ecosystem management. This is especially vital in ecosystems in the arid and semi-arid
regions. Pollinator ecology is another vital ecological process that is being ignored to the peril of
ecosystem health. The provision of suitable pollinator habitat matrices to ensure the pollination of the
vegetation will ensure the survival of plants that form the basic trophic level in ecosystems. This will
become increasingly important in future land management practices, and especially so in a One Health
approach to ecosystem management.
Epidemics are nothing more or less than “symptoms” of ecosystem disturbance. The causes and not the
symptoms should therefore be addressed, and the creation of fully functional ecosystems is an obvious
act. The illegal trade in wildlife and its products is spreading diseases over the world which could become
a major health risk soon.
Marine ecosystems are vast, covering much of the surface of the Earth. Yet many parts of the oceans are
oceanic deserts and marine ecosystems yield only a fraction of the total productivity of energy on the
Earth. Because of the misconception of being a limitless resource, marine ecosystems are currently under
severe threat of overutilization worldwide and should receive much more careful management.
Humans have already fragmented and abused many ecosystems which may be vital to their future health
and survival. They are much like economic crises where borrowing capital against an uncertain future has
already depleted many reserves. The only way in which to ensure the survival and sustainable
development of humans on the Earth is to balance their actions ecologically with the available renewable
natural resources. The creation of healthy ecosystems and the initiation of the One Health
concept/approach seem to be the only recourse. However, to do this will demand a total rethink and
linking of many scientific enterprises.
The concept of One Health emphasizes the fact that no ecosystem can function optimally unless the
constituent elements of its food-web matrix function optimally. Because of the complexity of these
matrices, no scientific field can tackle the concept alone. There is no room for narrow, personal attitudes.
The only way in which to enable humans to survive even into the next century is to harness the existing
scientific expertise into interpersonal, interdisciplinary and inter-institutional cooperative programmes with
clearly stated objectives.
4|Page
Ecosystems and Ecology
Baobab savanna, Tarangire National Park, Tanzania - July 1996
5|Page