This document provides a literature review on the effects of top predators on biodiversity and ecosystem functions. It discusses how top predators regulate trophic cascades and food webs through controlling prey populations. The loss of top predators like wolves and lynx in Germany has allowed herbivore populations to increase, impacting vegetation. Reintroducing these predators could help control ungulate numbers and damage. The document also examines factors that reduce top predator populations in human-dominated landscapes, such as habitat loss, poaching, and conflicts with livestock.

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EFFECT OF TOP PREDATORS ON BIODIVERSITY
AND ECOSYSTEM FUNCTIONS
WRITE UP
By
SHILPI KUNDU
Matriculation # 21364752
Submitted in major fulfilment for
the requirement of the course
LOCATION SPECIFIC KNOWLEDGE IN FOREST AND NATURE MANAGEMENT
COURSE # SoSe 2014
Submitted to
Prof. Dr. Niko Balkenhol
Dept. of Wildlife Sciences
Faculty of Forest Sciences and Forest Ecology
Georg- August- University Goettingen
Busgenweg -3
GERMANY
Dated 14th
July 2014

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EFFECT OF TOP PREDATORS ON BIODIVERSITY AND
ECOSYSTEM FUNCTIONS
Background
In a successful ecosystem both producer (e.g. green plants and all photosynthetic organisms)
and different level consumers (The organism who cannot produce their own food) are
arranged in different trophic levels. Every species has its own role and one species never
perform the role of other species in the ecosystem (EU final report, 2012). Top predators are
those species whose position is at the top of the food chain such as lynx, bears, wolves,
whales, sea otters, lions, sharks, etc. They are smaller in number but larger in size so they
need very larger areas and for their safeguarding wider spatial scales need to be arranged and
they need larger prey for their food habituated (Petra et al., 2012). Top predators play an
important role in regulating the food web as they are at the top position of the trophic levels.
They have a great effect on ecosystem conservation (Ripple & Robert, 2012) and to keep the
ecosystem functional or active resulting maintain biodiversity. However, top predators are
being reduced in numbers due to human activities and climate change. Due to climate change
this predator migrates from one place to another place, alter their seasonal activities and
sometimes this climate change reduces the number of top predators (Craig et al., 2013). This
removal of top predators from ecosystem creates trophic cascades that favours herbivores
increased. During the last two centuries larger mammalian carnivore species have sharply
been reduced from the global ecosystem (Ripple & Robert, 2012; Ceballos & Ehrlich, 2002
and Ripple & Beschta, 2004). As top predators play an important role to manage ecosystem,
their loss affects the food chain length and both plant community and herbivores intensity
(Estes et al., 2011and Fretwell, 1987). So it is very important to understand the effect of top
predators on biodiversity and ecosystem management. Fig.1 shows the scenario of a food
web in a terrestrial’s ecosystem.
Fig: 1. Food web (http://images.tutorvista.com/content/feed/tvcs/Deciduous20forest20food20web.JPG)

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Statement of Problem
Top predators are one of the potential elements in the ecosystem and those have a positive
effect on biological diversity through regulating the trophic cascades (Letnic et al., 2012) so
their continuous losses from the environment can create a decline biodiversity. Larger
predators are habituated to have large energetic constraints, slow reproduction ability, low
population density, travels a lot for larger prey to meet their energetic requirements. (William
et al., 2014; Carbone et al., 1999; Cardillo et al., 2004). Historically, humans have modified
ecosystems by decimating native animal populations and often substituting domesticated
stock, thereby influencing food webs and simplifying interactions among species (Ripple et
al., 2009). On the other hand prey densities are also changing due to climate change. So the
biodiversity is affected and their existence in the ecosystem is continuously declining in
somewhere they are in endanger condition and somewhere they are extinct. If we try to
reintroduce them in the area where top predators are completely loss or endangered they may
overcome the situation by showing positive effect on the degraded ecosystem. If we
reintroduce top predator such as lynx (Lynx lynx) and wolves (Canis lupus) to German
ecosystem we may observe their influence on the local ecosystem properties. As human
activities play a vital role for the extinction of top predators, I tried to find out what factors
prevent top predators from fulfilling their ecosystem role. Therefore I tried to explore the
reviewed expert based information regarding –
a) The effects of top predators on biodiversity and ecosystems,
b) How the return of lynx and wolves to Germany might influence local ecosystem
properties, and
c) The factors which reduce top predators from human dominated landscape.
Methods and data used
The project report was prepared by reviewing literature, peer-reviewed articles, google search
and discussing with my supervisor. I use predator, top predator, predator effect, ecosystem
function, reintroduced top predators, species protection law, ecology of fear, biodiversity
regulator, trophic downgrading, behavioural pattern of prey and predator, food chain
dynamics, conflict of human with top predator and so on as key search words in google
search.
The effects of top predators on biodiversity and ecosystems
Ecosystem consists of both biotic and abiotic components. Biotic components of an
ecosystem are all living organism from the smallest (microorganism) to the top predator and
abiotic component consists of soil, water, air and also physical characteristics like
temperature, humidity, precipitation etc. There is strong relationship between living and non-

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living component. Non-living components determine the geographic distribution of both
plant and animal community and also influence successful growth of these biotic
communities.
According to the exploitation ecosystems hypothesis (EEH), there is a stepwise trophic
relationships among plants, herbivores, and predators (Oksanen et al., 1981 and Ripple &
Robert, 2012). EEH predicts a positive effect of plants and carnivores on net primary
productivity, while a negative relationship exists between top predators and herbivores,
because large predators consume herbivores and herbivores feed on the plant community.
From millions of years ago until present, top consumers have had a positive effect on the
environment (Estes et al., 2011).
-effect
+Indirect effect
-effect
Fig:2. Hypothetical Trophic cascades (Smee, 2010)
Fig.2. shows that each level has a negative impact of its immediate level in a trophic (Smee,
2010) and a positive impact of its distant level by controlling the consumer pressure. Utter
(Lutra lutra)- urchin (Echinus melo)- Kelp(algae-sea weeds) interaction is an example of
trophic cascades. Utter controls over the urchin resulting kelp population grow well. As we
know that trophic cascades are important in natural ecosystem and top predators’ position is
at the apex of food chain so they control over the food web and natural ecosystem (Terborgh
et al., 2010). If top predators become reduced from the trophic hierarchy then food chain
length become reduced and number of herbivores increase and this effect on primary
producers. When predators limit the consumer then primary producer that is bottom level will
indirectly benefited. Top predators control the prey population and our world is changing so
the food web is also changing and top predator extinction occurs. As a consequence number
of large herbivores increase. And the increased large herbivores alter the local vegetation,
change the movement of birds and small mammals for searching their food and habituated
those who are dependent on primary producers and alter other parts of the ecosystem in a
numerous ways. They not only feed the primary producer but also damage the tree by
browsing, bark stripping. It may be difficult to control erosion, high quality timber production
and other management goal that are related for forest regeneration (Partl et al., 2002 and
Top predator (Carnivors)
Intermediate consumers (Grazers)
Primary producer (Plant)

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Gerhardt et al., 2013). The influence of top predator is to suppress both the abundance and
distribution of the herbivore and to promote the abundance and production of primary
producers (Estes et al., 2011). So top predators can keep the ecosystem balanced by
managing biodiversity of the ecosystem. Large predators have an important role in carbon
sequestration. Extinction of top predator from the trophic has a great impact in climate
change (Ripple & Beschta, 2012). It reduces long term carbon sequestration due to lack of
woody plant and increase herbivores. So managing herbivores slow down the deforestation
and also increasing forest regeneration carbon sequestration can be increased and thus
conserve biodiversity (Ripple & Beschta, 2012). As large predator control over the large
herbivores that cause damage of the vegetation by grazing and soil erosion occur, so they
control over the soil erosion also.
In some area top predator has a negative impact on biodiversity. The reduction of large
herbivores increases the plant biomass, which fuelled wildfires during dry seasons in East
Africa (Estes et al., 2011). It’s a natural ecological process that renew or rebirth the
ecosystem. When forest fire increases, it becomes responsible for increasing releases of CO2
into the atmosphere. Due to this increase CO2 level the climate is changed which reduces
biodiversity of this ecosystem rapidly. The consumers are moved to another suitable place
and producers got problem to produce food for its own as well as for consumers due to
elevated CO2, drought, heat, storm etc.
When a specific wildlife population is huge, they perform to show signs of adverse effect on
the soil, vegetation or fauna, poor body condition scores, low trophy scores or low
reproductive performance, or increased parasitic burdens but also the measurement of
infectious disease prevalence (Gortázar et al., 2006). The European wild boar (Sus scrofa)
which is increasing its range keeps contri ution to the spread out of many diseases including
classical swine fever ujeszky s disease orcine ircovirus type and ovine tu erculosis
among others (Geisser & Reyer, 2004 and Gortázar et al., 2006). Deer which is another
species regarding the overabundance also contribute to mycobacterial disease transmission,
normally when they concentrate at feeding sites (Gortázar et al., 2006). If the top predators
are overabundant in the ecosystem, the nature has its own way to control the overabundant
top predator and keep the ecosystem active.
How the return of lynx and wolves to Germany might influence local ecosystem
properties
In the trophic cascades number of top predator is limited and in Germany there were only few
large predators - lynx, wolves and European brown bear and number of top predator became
reducing and at the beginning of twenty century their extinction occurred. Their extinction
occurred due to a combination of human factors, including with deforestation and losses of
natural prey population. (Trouwbors, 2010). When a steady declining of top predator started
along with deforestation, the top predator tries to compete with human being and attacking
the domestic animals because their shelter and food is limited due to this deforestation. Thus
conflict occurred between human being and top predator for their food and habituated. After
declining of top predator the prey population become increasing and at a certain time prey
population flourish. Due to the extinction of large predator number of herbivores such as

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different types of deer – roe deer (Capreolus capreolus), fallow deer (Dama dama) and red
deer (Cervus elaphus) increased. From a study conducted by Melis et al. (2009) on roe deer
density in Europe we found that top predators such as wolves and lynx control over the roe
deer density. With the presence of both lynx and wolf roe deer density is very poor while
absence of lynx or both wolves and lynx roe deer density is very high. And deer impact plays
an important role in ecosystem properties by altering the composition and structure of
vegetation (Gill & Beardall, 2001 and Gerhardt et al., 2013). Deer impact has a great value in
case of both environmental and society forest function and also timber production. They
cause a great damage not only the woodland but also agricultural land. Forest management is
an important tool to control over the ecosystem function (Gerhardt et al., 2013). Wolves
have a great control over elk (Cervus elaphus). When wolves’ extinction was occurred after
the mid of 1920s, elk population was increased. Ripple & Beschta (2004a) showed in a study
that with the extinction of wolves’ population elk increased and that increased elk consumed
and damage the willows (Salix sp.) to a great extent and after the retirement of wolves in
1996 the elk population began to decrease by predation and in 2000 the willows trees again
start to grow in Gallatin Range of South-western Montana, USA. Wolves manage the
ungulate population in lethal and non-lethal ways keeping the ecosystem function active and
conserve biodiversity in Gallatin Mountains. If we introduce a new species into an ecosystem,
competition will be arising and entire ecosystem will be disturbed. In some area the lynx and
wolves are reintroduced for regulating ungulate populations that represent a management
action by restoration the composition and vegetation structure and conservation of
biodiversity. From forest management principle in Germany the principle close to nature
forestry (CNF) describes regulating ungulate populations (Lecture note, 2014): Ungulate
populations higher than under natural conditions due to lack of large predators. They damage
regeneration (quality reduction) or hinder the natural regeneration, game management
necessary, so forests can regenerate naturally. Predator and prey are always engaged in games
of stealth and fear. There are two approaches of predator prey interrelationships. First one is
predators regulate the population size of large herbivores by causing direct mortality and
second one is predators create fear for the prey and thus changing their behaviour (Brown et
al., 1999). As a result the prey population may change their way of movement or they feed
another plants that has low risk. They reduce their feeding time as a result some are died due
to starvation mortality (Schmitz et al., 1997).
As wolves, lynx, etc. are the top predator in Germany and they are near to be extinction so if
we reintroduce them then they may be able to control the ungulate population by causing
direct death or frightened them in their normal behaviour and that will create a favourable
situation for natural regeneration and normal growth of plant community and biodiversity
will maintain. Non-lethal effect that means ecology of fear is more important than direct
mortality (Schmitz et al., 1997 and Ripple &Robert, 2003) because by creating fear their
reproduction rate also foraging ability will decrease and forest biodiversity will be restored.
From a study of Laundré et al. (2001) reintroduced wolves in Yellowstone forest, USA; it
shows that wolves control elk and bison (Bison bison) by providing fear rather than killing
those resulting change of behaviour of prey population. Female showed higher more
awareness in the area where wolves were available in the Yellowstone forest rather than
wolves free areas. The female elk along with calves showed highest vigilance (47.5 ± 4.1%;

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mean ± SE) in the second year and continued up to third year after that vigilance were
reducing.
Another effect that caused by reintroduced wolves and lynx is that they may attack human
and other livestock although they prefer wild prey for their food habit or they may serve as
recreation by attraction of tourist and thus may play an ecotourism function. As Germany
forestry has a patchy environment along with agricultural land and settlement so there
remains a conflict between human being with top predators along with food and habituated as
top predators are medium to large bodied animal so they need more space for their roaming.
But in the Bern Convention Action Plan for the lynx states that lynx is not dangerous to the
people (Trouwborst, 2010) and wolves have a tendency to avoid direct contact of human
being so the risk of wolves attack is very poor. But sometime the aggressive wolves attack
human being and killed them. Mostly children, treated as prey were attacked by healthy
wolves. When reintroduction of both wolves and lynx occurred in the same place, there may
occur a conflict within the top predator. Wolves sometimes prey the lynx.
The factors that reduce top predators in human-dominated landscapes
Top predators play a vital role and their existence in the human dominated landscapes and
also performing ecosystem role needs a better understanding of interaction between predator
and human. If we reintroduce top predator in an ecosystem then a lot of factors such as
availability of predator, competitors, poaching, weather condition, genetic isolation, and most
important factor human activities affect them in their growth, survival and reproduction.
Germany is a diversified land with complex climatic condition. In Germany more than 50%
land is used in agriculture and in the previous year forest area was higher and it reaches
around 30% due to forest loss and land fragmentation, grazing, modification of forest
habituates and also agricultural intensification. Due to deforestation and agricultural
intensification number of large herbivores reduces and the reintroduced top predators such as
lynx, wolves, etc. they attack livestock animal such as sheep husbandry in Europe (Thirgood
et al., 2005) and so there remains conflict between farmers and the top predator in order to
keep their livestock safe and it would be difficult to sustain for the large species in a small
area and in near future they could be unavailable due to potential threat from human. They
may be a threat of human being also. In Central Europe, Asia and North America farmers
use livestock protection (guarding) dog to protect their livestock such as goat, sheep from
predation. (Gehring et al., 2010) The livestock protection dogs are able to reduce disease
transmission from wildlife to livestock husbandry, as well as conserve wildlife population.
They may serve as green tools and also offer a proactive function for allowing livestock
boundary and wildlife to coexist. Their performance depends on their aggressiveness. But
sometimes it creates a lot of problem to surrounding people and also tourist. They can bite the
people. Sometime they may feed on domestic dog. Hunting both legal and illegal is an
important factor that prevent top predator from fulfilling their ecosystem role in human
dominated landscape. Construction of road inside the forest area creates another problem for
the top predator. Constructed road also increase the road mortality rate of reintroduced top
predators due to accident with vehicles in the forest (Andrews, 1990).

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Conclusion
So there is an interrelationship between different trophic levels. Every stage plays a great role
in ecosystem function and thus maintaining biodiversity. Top predator keeps the great
contribution in the trophic cascades by reducing number of prey population and influencing
the increment of primary producers. In European ecosystem top predators such as lynx,
wolves, bear were extinct at the beginning of 20th century. So their absence alters the tropic
cascades and biodiversity losses and ecosystem function disrupted. According to the
European Union species protection law some top predators are reintroducing in the European
ecosystem, they are fulfilling the role of ecosystem by managing the inflation of their prey
population. The top predators regulate the ungulate prey population by feeding them or by
creating fear of the prey population and thus stopping the reproduction and thus influence the
growth of primary producers. But human being plays an important role to stop the top
predator for their ecosystem services. As they become a fear both human and livestock, there
remains conflicts between them and for that human beings take direct step to control them.
As a proactive function some preventive measures can be taken by the farmers but problem is
to get livestock damage compensation form the insurance company because the insurance
company does not give any return if the livestock are damaged by the predator that may be
very costly in some cases. So human plays an important role to prevent the top predator by
fulfilling their ecosystem services and thus biodiversity is affected in human dominated
landscape and thus reintroduction of top predators becomes a challenges in Germany. For the
returns of top predators stronger efforts are necessary to provide both financial and structural
safeguard. Hunters may keep an important role in facilitating the top predators to return their
home in Germany.
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Acknowledgements
I would like to thank Prof. Dr. Niko Balkenhol the supervising faculty for the valuable
guidance and supervision during project report preparation. My thanks are also due to Prof
Dr. Aelxander Knohl, Programme Coordinator and Prof. Dr. Niels Strange, SUFONAMA
Coordinator for giving opportunity to study this course.