Environmental problems – An overview - Environmental Deterioration and Contamination: Problems and their Management - page 33

properties, innovative agro-technologies and eco-technologies, pragmatic science
and engineering may stop ecosystem deterioration.
We pick up two drivers from the long list: deterioration of ecosystems by invasive
species and problems of the urban ecosystem. Both of these problems are complex and
“only'' indirectly related to environmental contamination, but demonstrate complexity
and interactions between ecological systems, intensive human land uses with multiple
chemical application as well as socioeconomic aspects.
6.5 Invasive species
Globalization involves the closer integration of socioeconomic and ecological systems.
The common initiative of The Ecological Society of America (ESA, 2013) and Society
for Ecological Restoration International (SER, 2013) is an integrated sustainability sci-
ence (ESA-SER Joint Meeting, 2007). Integration of ecological systems occurs through
the intentional or incidental movement of species associated with growth in trade
and travel. Species movement has certain potential but uncertain consequences. These
include the emergence of novel zoonotic diseases along with changes in the diversity
and structure of local species assemblage that affect the capacity to deliver ecosystem
services. In many cases, the effect is ecosystem homogenization with implications for
both the correlation of risks across space and the resilience of individual systems. The
resulting “portfolio effect'' alters responses to environmental stressors.
An invasive species is occurring beyond its accepted normal area of distribution as
a result of human activities. The overrepresentation of a species threatens ecological
services and may have major impact on biodiversity by reducing overall species abun-
dance and diversity. Invasive species include microorganisms causing diseases and pest,
fungi and parasites, feral animals, insects and other invertebrates, introduced marine
pests and weeds.
The definition has been revised during the past years. Initially, only the non-
indigenous species were considered invasive, but today both native (indigenous) and
non-native species are regarded invasive if they disrupt a particular habitat by domi-
nant colonization. As a result of the presence and dominance of invasive species, the
natural control and balance are destroyed and the regulating services of the ecosystem
are deteriorated.
Invasive species have generally high adaptive capacity to environmental conditions
and substrates, they are able to reproduce rapidly both asexually and sexually, plants
can regenerate from the root, grow and disperse fast because their natural competitors
and predators that keep them in check in their original ecosystems are missing. The
trophic balance of the community may be highly disturbed by an invasive species, given
that the fast growing population selectively utilizes the supply formerly shared by a
stable and balanced community. Mainly the minor/weaker members of the community
are reduced by the dominating behavior of the invasive species.
Invasive species may be the ones introduced or those which overrun the normal
population density due to natural or man-made changes of the habitat (e.g., excess
precipitation, increased nutrient supply, misused agrotechnologies). The geographical
expansion of certain species can also be considered as invasion, which is a natural
trend over the long term. However, non-native species can also have benefits.