24
nected into an ecological network have an essential role in maintaining the species diversity of
the biosphere.
The spatial distribution of the unknown
number of the 10–20 million species of the biosphere on Earth (certain estimations consider
even much higher numbers also realistic) is not
random. The appearance and regular occurrence
of ecosystems is determined significantly by
climate. The appearance of tropical rainforests,
savannahs, deserts or deciduous forests in temperate climate zones is different and their occurrence more or less parallel with latitudes is
well-known.
The above zonal occurrence of terrestrial ecosystems and the zones themselves were named
after the major plant types (formations), however,
they mean more than simple plant zones: they
include all ecosystems in the given zone including their plants and animals, producing and
decomposing organisations and also their habitats. These are called biome in ecology and life
geographical zone in geography. Only the most
elemental characteristics are discussed here.
Aquatic ecological systems have not been
grouped into biomes yet. The reason for this is
primarily that the living systems in oceans are
divided differently from terrestrial ecosystems
both horizontally and vertically. Unknown
patches are especially abundant in the study of
deep-sea ecosystems. It is likely that studying the
life of oceans will result in the systemising of the
major life geographical units of oceans, marine
biomes in the future.
Biosphere itself as the global ecological system is interpreted as a unity of all terrestrial and
aquatic ecological systems (ecosystems).
2.4
Topology of Systems:
Network Theory
Connections, interactions among the elements of
a system in many cases determine the operation,
stability of the entire system. In the last third of
the twentieth century increasing attention was
paid to the connections of the elements of complex systems. Scientists of different fields understood that completely different systems have
similar structure. For example, the Internet created by humans is very similar to living organisms in many ways, the economic networks are
similar to networks observed in living cells, etc.
To understand the operation of complex systems
the understanding of the structure of networks is
necessary.
In mathematics system elements are called
points and connections between them are called
sides. Sides may represent either strong or weak
connections. According to Granovetter (1983)
the society is composed of groups of friends with
a small number of members connected strongly
and these groups have weak connections with
each other (Fig. 2.7). Weak connections are not
insignificant, these could be dominant in communication with the wider world. Job seeking could
be set as an example. It is rarely successful as the
job seeker would like within the groups of friends
with strong connections therefore our weaker
connections reaching further have to be utilised.
Watts and Strogatz (1998) introduced group
strength coefficient (local clustering coefficient/
clustering coefficient). A value close to one
means that in a group of friends every friend of a
given person is a good friend of the others (networks B, C and D in Fig. 2.7). If the cluster coefficient is zero then the given person is the only
one who keeps the group of friends together (network A in Fig. 2.7).
Scientists realised that group formations a
general characteristic of complex networks. It is
present in the network of neurons of living beings
just like in electric networks or the World Wide
Web.
The structure of the World Wide Web is dominated by points having many connections, socalled centre points. These are the ones everyone
refers to therefore they are easy to find. Yahoo.
com, for example, is a huge centre point that can
be accessed with two to three clicks from practically any webpage. Centre points occur in almost
every major studied network, they are universal
building blocks of our complex, connected world.
Therefore they are present in natural systems as
well, like in ecological systems or in the biochemical system of our cells.
2 Structure and Operation of Systems, Models of the Global Earth System
nected into an ecological network have an essential role in maintaining the species diversity of
the biosphere.
The spatial distribution of the unknown
number of the 10–20 million species of the biosphere on Earth (certain estimations consider
even much higher numbers also realistic) is not
random. The appearance and regular occurrence
of ecosystems is determined significantly by
climate. The appearance of tropical rainforests,
savannahs, deserts or deciduous forests in temperate climate zones is different and their occurrence more or less parallel with latitudes is
well-known.
The above zonal occurrence of terrestrial ecosystems and the zones themselves were named
after the major plant types (formations), however,
they mean more than simple plant zones: they
include all ecosystems in the given zone including their plants and animals, producing and
decomposing organisations and also their habitats. These are called biome in ecology and life
geographical zone in geography. Only the most
elemental characteristics are discussed here.
Aquatic ecological systems have not been
grouped into biomes yet. The reason for this is
primarily that the living systems in oceans are
divided differently from terrestrial ecosystems
both horizontally and vertically. Unknown
patches are especially abundant in the study of
deep-sea ecosystems. It is likely that studying the
life of oceans will result in the systemising of the
major life geographical units of oceans, marine
biomes in the future.
Biosphere itself as the global ecological system is interpreted as a unity of all terrestrial and
aquatic ecological systems (ecosystems).
2.4
Topology of Systems:
Network Theory
Connections, interactions among the elements of
a system in many cases determine the operation,
stability of the entire system. In the last third of
the twentieth century increasing attention was
paid to the connections of the elements of complex systems. Scientists of different fields understood that completely different systems have
similar structure. For example, the Internet created by humans is very similar to living organisms in many ways, the economic networks are
similar to networks observed in living cells, etc.
To understand the operation of complex systems
the understanding of the structure of networks is
necessary.
In mathematics system elements are called
points and connections between them are called
sides. Sides may represent either strong or weak
connections. According to Granovetter (1983)
the society is composed of groups of friends with
a small number of members connected strongly
and these groups have weak connections with
each other (Fig. 2.7). Weak connections are not
insignificant, these could be dominant in communication with the wider world. Job seeking could
be set as an example. It is rarely successful as the
job seeker would like within the groups of friends
with strong connections therefore our weaker
connections reaching further have to be utilised.
Watts and Strogatz (1998) introduced group
strength coefficient (local clustering coefficient/
clustering coefficient). A value close to one
means that in a group of friends every friend of a
given person is a good friend of the others (networks B, C and D in Fig. 2.7). If the cluster coefficient is zero then the given person is the only
one who keeps the group of friends together (network A in Fig. 2.7).
Scientists realised that group formations a
general characteristic of complex networks. It is
present in the network of neurons of living beings
just like in electric networks or the World Wide
Web.
The structure of the World Wide Web is dominated by points having many connections, socalled centre points. These are the ones everyone
refers to therefore they are easy to find. Yahoo.
com, for example, is a huge centre point that can
be accessed with two to three clicks from practically any webpage. Centre points occur in almost
every major studied network, they are universal
building blocks of our complex, connected world.
Therefore they are present in natural systems as
well, like in ecological systems or in the biochemical system of our cells.
2 Structure and Operation of Systems, Models of the Global Earth System