Urban fauna: Geochemical aspects of existence
Dr. Vladimir A. Alekseenko - Institute for Water and Environmental Problems of the Siberian Branch of the Russian Academy of Sciences
Urban ecosystems are to a certain extent isolated from various other geochemical¬†landscapes. Although occupying relatively¬†small territory (less than 6 % of the Earth‚Äôs¬†land surface), urban areas give a shelter for the¬†prevailing part of the humanity. In this regard,¬†environmental assessment of cities, as well as¬†studies of favourable developmental conditions¬†of urban fauna are of paramount importance.
Several primary reasons caused the current¬†ecological problems. First, the natural (wild)¬†fauna of suburbs is gradually included into the¬†growing urban areas that develop the adjoining¬†territories (Burden, 2006; Gonz√°lez-Garc√≠a¬†et al., 2009). Secondly, the areas surrounding¬†the city have become widely used by urban¬†residents and biogenic landscapes ‚Äď steppes,¬†forests etc. ‚Äď have begun to transform into¬†technogenic areas, mainly agricultural, road¬†and industrial ones.¬†This has caused significant¬†migration of fauna from suburbs to settlements¬†(Garden et al., 2006; Luniak, 2004). This¬†process primarily involves birds and rodents.¬†Third, the number of wild (e.g., squirrels)¬†and domestic animals has increased (Rhodes¬†et al., 2011).
All the appearing fauna has moved to the¬†cities carrying diseases, and got to unusual¬†conditions, which is most important and in¬†most cases has a negative impact. As a result, many illnesses of terrestrial animals and¬†birds have become dangerous to humans.
In accordance with the Law of chemical element¬†behaviour in the biosphere (formulated¬†by V. A. Alekseenko in 1992, 2006, 2017), the¬†content, distribution and even occurrence¬†forms of chemical elements are particularly¬†transformed in residential landscapes as¬†compared with natural ones. For instance,¬†the role of technogenic migration and accumulation,¬†superimposed on natural processes,¬†has significantly increased. Moreover, in¬†the vast majority of cases, the consequences¬†of technogenesis are paramount.
Under the influence of numerous anthropogenic¬†factors, such as electromagnetic,¬†thermal, sound (noise), radioactive, light¬†16 pollution, the composition of living matter¬†can undergo certain changes. In accordance¬†with the Law of connection between changes¬†within a single landscape (formulated by V.¬†A. Alekseenko in 1992), these changes affect¬†over time the geochemical characteristics of¬†the urban atmosphere, groundwater and ultimately¬†the fauna life quality.
As the chemical elements are transported¬†to residential landscapes both as a result of¬†normal regional natural processes and as a¬†result of technogenesis, geochemical anomalies¬†are often formed in various city zones as¬†compared with the surrounding natural areas.¬†Considering the occurrence conditions of¬†such anomalies, they should be classified as¬†natural-technogenic and polygenic.
Their particular feature is a partial overlay of¬†anomalies made up by various chemical elements. Thus, these anomalies can be considered¬†as multi-component, different from natural¬†analogues. First, urban anomaly (or rather,¬†group of anomalies) presents the pollutants¬†in different forms. Secondly, the pollutants¬†are usually presented by numerous chemical¬†elements (compounds) that do not have common¬†crystal-chemical properties. The extreme¬†irregularity of pollutant abundances should be¬†noticed as a particularity of urban anomalies.
Let us first consider several properties of the¬†atmochemical anomalies in the near-ground¬†air of residential landscapes:
1. The composition of atmospheric gases in¬†urban areas is significantly different from¬†that of natural (biogenic) landscapes. In¬†fact, in cities, we are dealing with a large¬†technogenic atmochemical anomaly, made¬†up of various pollutants and which is, from¬†this point of view, polygenic. For example,
an atmochemical anomaly over a megacity,¬†with a population of over a million, various¬†industries and vehicles produce approximately¬†1,500 tons of hydrocarbons, over 600¬†tons of nitrogen oxide, 5,000 tons of carbon¬†monoxide, 500 tons of sulphur oxides etc.¬†daily. About 90 tons of various aerosols are
also emitted into the air.
2. This anomaly over large settlements is¬†absolutely inhomogeneous and is divided¬†into smaller ones, differing in composition¬†and contents of gases. Over 30% of aerosols¬†come from vehicles, and nitrogen oxides are¬†derived from fuel combustion. Accordingly,¬†a spatial relationship exists between anomalies¬†and pollutants.
3. Location of certain atmochemical anomalies¬†in cities is not strictly fixed in different¬†districts. These anomalies are mobile,¬†depending on pollutant content, and can¬†even completely disappear with changing¬†weather conditions and hours of enterprise¬†and transport operation.
The urban waters are characterised by the¬†following features:
1. The content of components allows consideration¬†of urban water bodies as major¬†technogenic hydrochemical anomalies;
2. In such aqueous anomalies, the distribution¬†of contaminants, as well as oxidation-reduction¬†and acid-alkaline characteristics are¬†patchy;
3. The contents of priority pollutants are¬†determined by nearby industries and vary¬†depending on seasons and even years. For¬†example, in the centre of a megacity the Ca¬†contents in the groundwater is often 10‚Äď20¬†times higher than the contents in the suburbs,¬†and the element content in summer¬†is 1.5 times higher than in winter.
Vegetation of urban areas is different from¬†a plant cover of landscapes surrounding settlements:
1. Urban plants represent a geobotanical¬†anomaly compared to a vegetation cover of¬†suburbs. It differs in species composition of¬†plants; the rate of branch growth, chlorosis,¬†necrosis, stag-headedness, die-away of small¬†tree branches; drying and withering.
2. The contents of numerous chemical elements¬†in urban vegetation differ significantly¬†from their contents outside the settlements.¬†This allows consideration of a city¬†as a large multicomponent biogeochemical¬†anomaly.
3. Development of biogeochemical and geobo- 17¬†tanical changes in the vegetation of urban¬†areas is mosaic.
4. The specificity of occurrence of urban biogeochemical and geobotanical anomalies,¬†in conjunction with leaf-litter removal,¬†results in the unique biological cycle of chemical¬†elements, typical only for residential¬†landscapes. This, in turn, makes specific¬†conditions of migration and accumulation of
chemical elements in the urban soils (Tume¬†et al., 2018).
In accordance with the Law of development¬†of ecological-geochemical changes within a¬†single landscape, atmochemical, hydrochemical,¬†biogeochemical anomalies within a¬†single urban area, make up a city-wide lithochemical¬†(soil) anomaly. In partnership with¬†academician N.P. Laverov a special research¬†methodology was designed, analysis methods¬†(often for reliability, duplicating one another)¬†were chosen and the leading laboratories were¬†determined.
All these issues were considered¬†in detail in peer-reviewed monographs and¬†articles (Alekseenko, Alekseenko, 2013, 2014a,¬†2014b). We only note that the geochemical¬†characteristics of soils of over 300 cities in¬†Europe, Asia, Africa, Australia and America¬†were studied; a number uniformly selected¬†samples in several settlements reached several¬†thousands, but mainly ranged from 30 to 100.
All the work on establishing abundances of the¬†chemical elements in urban soils took some¬†20 years. The obtained data were compared¬†with abundances in the Earth‚Äôs soils (Table 1),¬†characterising the geochemical patterns of the¬†soils of the late XX ‚Äď early XXI centuries. It¬†is clear that over time abundances of certain¬†elements will change, especially being influenced¬†by changing technologies implemented by¬†urban enterprises.
Biogenic migration and the presence of living¬†organisms largely determine the characteristics¬†of the ecological-geochemical state of the¬†environment and are the leading features of¬†the classification of geochemical landscapes,¬†including urban ones. People make up the¬†significant zoomass in cities. They determine¬†the leading technogenic migration; constitute¬†an important part of the biological cycle;¬†take part in the direct extermination and¬†the emergence of new types of urban fauna.
With this circumstances, residential landscapes¬†were divided into groups depending¬†on the number of inhabitants (Alekseenko,¬†Alekseenko, 2013, 2014b). Average contents¬†of the chemical elements in the soils of such¬†groups are given in Table 2.
Even a cursory analysis of the information obtained allows to draw the following general conclusions:
1. Urban soils inherited the extreme unevenness¬†of distribution of chemical elements¬†and the connection of their contents with¬†atomic mass from the natural Earth‚Äôs soils,¬†which led to the predominance of light and¬†even-numbered elements.
2. Contemporary soil geochemical patterns¬†are primarily formed under the technogenic¬†impact. The concentrations of B, Ba, Ca, Cl,¬†Hg, Li, P, Pb, Sr and Zn are elevated due to¬†this impact. These chemical elements have a¬†paramount influence on all living organisms¬†in cities, including the wild and domestic¬†fauna.
3. Such elements which concentrations exceed¬†the levels of the Earth‚Äôs soils Ag (5.3 times),¬†As (9.4), Bi, Mo (2.2), Sn (2.7), W and Yb¬†(1.5) may affect the life quality of urban¬†organisms.
4. In the soils of certain settlement groups,¬†divided by the number of residents, average¬†contents of chemical elements differ¬†significantly. Megacities with over a million¬†of inhabitants, the highest number of¬†elements with high average concentration¬†was found (Pb, Zn, Ag, As, Cu, Mn, Co, Ni,
Ti and Sn). The smallest number of chemical¬†elements with the heightened average¬†content is typical for soils of small towns,¬†villages, hamlets and farms. This must be taken into account when considering the¬†existence comfort of organisms.
5. The established abundances of the elements¬†in urban soils are their geochemical (ecological
and geochemical) characteristic,¬†which reflects the simultaneous combined¬†impact of technogenic and natural processes.¬†With the development of science and¬†technology, the abundances may gradually¬†change. The rate of such changes is merely¬†predictable.
Alekseenko V., Alekseenko A. (2014a) The abundances of chemical elements in urban soils. Journal of Geochemical¬†Exploration, 147 (B): 245‚Äď249.
Alekseenko V.A., Alekseenko A.V. (2013) Chemical elements in geochemical systems. The abundances in urban¬†soils. Publ. House of South. Fed. Univ., Rostov-on-Don. 388 pp.
Alekseenko V.A., Alekseenko A.V. (2014b) Chemical elements in urban soils. Logos, Moscow. 312 pp.
Burden D. (2006). 22 benefits of urban street trees. Retrieved from http://www.walkable.org/download/22_benefits.pdf
Garden J., McAlpine C., Peterson A., Jones D., Possingham H. (2006) Review of the ecology of Australian urban¬†fauna: A focus on spatially-explicit processes. Austral Ecology, 31, 126-148.
Gonz√°lez-Garc√≠a A., Belliure J., G√≥mez-Sal A., D√°vila P. (2009). The role of urban greenspaces in fauna conservation:¬†The case of the iguana Ctenosaura similis in the ‚Äėpatios‚Äô of Le√≥n city, Nicaragua. Biodiversity Conservation,¬†18, 1909‚Äď1920.
Luniak M. (2004) Synurbization – adaptation of animal wildlife to urban development. Proceedings4th International¬†Urban Wildlife Symposium, 50‚Äď55.
Rhodes J.R., Ng C.F., de Villiers D.L., Preece H.J., McAlpine C.A., Possingham H.P. (2011). Using integrated population¬†modelling to quantify the implications of multiple threatening processes for a rapidly declining population.¬†Biological Conservation, 144, 1081‚Äď1088.
Tume P., Gonzalez E., King R.W., Monsalve. V, Roca N., Bech J. (2018) Spatial distribution of potentially harmful¬†elements in urban soils, city of Talcahuano, Chile. Journal of Geochemical Exploration, 184, B, 333‚Äď344.
Article published at the Catalan Academy of Veterinary Sciences‘s annual magazine, 2018 edition.¬†