Birds of prey accumulate environmental pollutants distributed in the surroundings and, in some cases, these can cause death. A comparative study of raptors in Galicia and Extremadura undertaken by Spanish researchers has confirmed their exposure to two potentially toxic agents, lead (Pb) and cadmium (Cd). The data obtained can be used to detect the toxicological effects in terrestrial ecosystems.
Birds of prey that live in extensive geographical areas can accumulate high levels of heavy metals and metalloids in their bodies, as they are top of their food chain. Now researchers from the Universidad de Extremadura and from the Universidad de Santiago de Compostela can reveal that these wild animals can provide extremely useful data to detect and evaluate the toxicological effects of different inorganic elements in terrestrial ecosystems. This information could also be extrapolated to human beings.
“The comparative study between the two autonomous communities, Galicia and Extremadura, enables the difference in exposure and accumulation to different chemical elements in diurnal and nocturnal raptors to be established”, Marcos Pérez López explains to SINC. He is the principal researcher for the study and is part of a wider project that will incorporate data from other countries in the EU.
The research has been published recently in the journal entitled ‘Ecotoxicology and Environmental Safety’, and establishes what type of bird tissue hyper-accumulates metallic elements such as cadmium (in this case the kidneys) would be the most suitable in biological monitoring studies. The research also establishes how the geographic area and the diurnal and nocturnal habits of the raptors can influence the elements quantified.
The scientists analysed the samples from different biological tissues, using the inductively coupled plasma mass spectrometer (ICP-MS) technique to detect and quantify the metals after the samples had been digested in an acid mixture. The Centros de Recuperación de Vida Salvaje (Wild Life Rescue Centres) in Galicia and Extremadura donated the dead birds in which pollutants were detected.
Raptors are sentinels of pollution
The results show that the levels of Zinc (Zn) and Arsenic (As) in the liver appear to be low in general and would not in any way pose a risk to the species under consideration. On the other hand, “the levels of Lead (Pb) in certain diurnal raptors, and levels of Cadmium (Cd) in other nocturnal raptors could lead to the assumption that a ecotoxicological risk exists which would indicate that promoting the biological monitoring networks is useful” Pérez López states.
In order to prevent this situation and predict future environmental changes, these researchers point out the importance of the ecotoxicological studies, particularly because “the raptors’ biological characteristics make them useful “sentinels”, who act as local monitors suitable for evaluating pollution levels”. The wild birds, studied as environmental pollution bioindicators, give important information about the effects of metals on certain species.
Heavy metals in the environment
Metals are found throughout the world and their presence can be associated with natural events or are the result of anthropogenic activities. The impact of heavy metals on the environment can be a serious threat for the stability of the ecosystem and cause serious effects to the health of animals.
Two of the toxic elements studied in this research, Lead (Pb) and Cadmium (Cd) are released into the environment extensively by industry, road traffic and fossil fuel consumption.
Once metals come into contact with a bird, they tend to accumulate in different organs, such as the kidneys and the liver, and can lead to serious damage, even the death of the animal itself.
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