Invasive species may represent ecosystem engineers (goats, for example) or
members of a new guild (rats, for example) and cause the extinction of native and
endemic species, for example on islands or habitat islands in continental regions
(Fukami et al. 2006; Whittaker and Fernández-Palacios 2007; Harris 2009; Hilton
and Cuthbert 2010; Jones 2010). The increase of a population of an invasive species
is only possible if relating resources are available.
Humans are able to behave like natural disasters and ecosystem engineers as well.
However, at local or regional scales they have already shown that they are also able
to behave in a more or less sustainable manner.
Humans use landscapes and ecosystems to get space, natural products, and
recreation. In the first case (space) natural ecosystems are destroyed or heavily
impacted to establish settlements, infrastructure, arable land, forestry or mining.
For earning energy, water and food, ecosystems are established as, or altered to,
semi-natural ecosystems. In many cases, the quality (organic farming), productivity
(quantity per time) and/or biomass in total (quantity) are the targets of the use. The
consumption of energy, water, food and other products under different scenarios are
expected to increase furthermore within the next years or decades (cf. Hussien et al.
2017; International Resource Panel 2017; Kurian 2017; Newth et al. 2017).
Humans change structures and reduce the biomass by harvesting organic or
inorganic material from the ground (including water) or biosphere. Additionally,
they increase the net productivity by supplying of material such as fertilizers, water
or lime. Humans alter landscapes and landscape structures, and reduce the species
diversity via ecosystem engineering, i.e. by directly eliminating trees, shrubs or
weeds, by hunting or using pesticides, and they can increase the local or regional
species diversity by changing ecological conditions, e.g., by moderate mowing of
semi-dry grassland, by planting or introducing neobiota. However, depending on the
intensity, many processes can have positive and negative effects on the species
richness (Pyšek et al. 2017; van Kleunen et al. 2015).
The swim bladder of a fish species called Totoaba (Totoaba macdonaldi), living
in the Gulf of California, Mexico, is an extremely expansive commodity for the
preparation of a culturally significant soup in China. However, nobody is interested
in the extinction of the worlds smallest marine mammal—a toothed whale called the
Vaquita (Phocoena sinus), which means little cow in English, and is endemic to the
Gulf of California; this animal is definitely at the brink of extinction. In which way
are Totoaba and Vaquita connected? The killing of the Vaquita is not intentional. The
population of this species strongly declined during recent decades simply because of
unmoderated and illegal resource use technologies (gillnets) for catching Totoaba,
eventually accompanied with pesticide exposure and/or inbreeding depression
(IUCN Redlist; see iucnredlist.org on the internet). These practice have depleted the
Vaquita as bycatch and simultaneously depleted their food sources. The ecosystem
functions of the Gulf of California will likely not change much when the last
Vaquita individuals have gone. This could be true for many predators on top of
the food web also in other ecosystems.
Landscapes that are used for recreation are often characterized by openness (1),
diversity of structures and/or species (2), and water bodies (3). Large herbivors, birds
90
C. Hobohm and S. E. Vanderplank
members of a new guild (rats, for example) and cause the extinction of native and
endemic species, for example on islands or habitat islands in continental regions
(Fukami et al. 2006; Whittaker and Fernández-Palacios 2007; Harris 2009; Hilton
and Cuthbert 2010; Jones 2010). The increase of a population of an invasive species
is only possible if relating resources are available.
Humans are able to behave like natural disasters and ecosystem engineers as well.
However, at local or regional scales they have already shown that they are also able
to behave in a more or less sustainable manner.
Humans use landscapes and ecosystems to get space, natural products, and
recreation. In the first case (space) natural ecosystems are destroyed or heavily
impacted to establish settlements, infrastructure, arable land, forestry or mining.
For earning energy, water and food, ecosystems are established as, or altered to,
semi-natural ecosystems. In many cases, the quality (organic farming), productivity
(quantity per time) and/or biomass in total (quantity) are the targets of the use. The
consumption of energy, water, food and other products under different scenarios are
expected to increase furthermore within the next years or decades (cf. Hussien et al.
2017; International Resource Panel 2017; Kurian 2017; Newth et al. 2017).
Humans change structures and reduce the biomass by harvesting organic or
inorganic material from the ground (including water) or biosphere. Additionally,
they increase the net productivity by supplying of material such as fertilizers, water
or lime. Humans alter landscapes and landscape structures, and reduce the species
diversity via ecosystem engineering, i.e. by directly eliminating trees, shrubs or
weeds, by hunting or using pesticides, and they can increase the local or regional
species diversity by changing ecological conditions, e.g., by moderate mowing of
semi-dry grassland, by planting or introducing neobiota. However, depending on the
intensity, many processes can have positive and negative effects on the species
richness (Pyšek et al. 2017; van Kleunen et al. 2015).
The swim bladder of a fish species called Totoaba (Totoaba macdonaldi), living
in the Gulf of California, Mexico, is an extremely expansive commodity for the
preparation of a culturally significant soup in China. However, nobody is interested
in the extinction of the worlds smallest marine mammal—a toothed whale called the
Vaquita (Phocoena sinus), which means little cow in English, and is endemic to the
Gulf of California; this animal is definitely at the brink of extinction. In which way
are Totoaba and Vaquita connected? The killing of the Vaquita is not intentional. The
population of this species strongly declined during recent decades simply because of
unmoderated and illegal resource use technologies (gillnets) for catching Totoaba,
eventually accompanied with pesticide exposure and/or inbreeding depression
(IUCN Redlist; see iucnredlist.org on the internet). These practice have depleted the
Vaquita as bycatch and simultaneously depleted their food sources. The ecosystem
functions of the Gulf of California will likely not change much when the last
Vaquita individuals have gone. This could be true for many predators on top of
the food web also in other ecosystems.
Landscapes that are used for recreation are often characterized by openness (1),
diversity of structures and/or species (2), and water bodies (3). Large herbivors, birds
90
C. Hobohm and S. E. Vanderplank