Abstract
The accelerated and disordered growth of large urban centers has caused a significant loss of biodiversity and the negative effects are more significant in aquatic environments. Thus, the objective of this study is to assess the effects of environmental change due to urbanization in the abundance and biomass patterns of species belonging to the Zygoptera suborder. We tested the hypothesis that, in altered streams, there will be a predominance of organisms with fast growth and small biomass (r-strategists), and intermediate streams will have an overlapping of r and k-strategists. In control streams, there will be a predominance of k-strategists, with slow growth, decreased abundance, and high biomass. Urban expansion in Amazonian streams will cause loss of Zygoptera species richness. Streams draining urban areas will have higher air temperatures than control streams. Thus, small-sized and less abundant species will be favored. We sampled 15 streams in the metropolitan area of Belém. Sites were classified, using the index of physical habitat integrity, as control, intermediate and altered. Comparisons between biomass and abundance were analyzed using W Statistics. Our analyses showed that: the effects of urbanization cause loss of k-strategists and favors r-strategists, once abundance was placed above biomass; in intermediate environments, contrary to what we expected, there was no overlapping of strategies, once r-strategists were also placed above k-strategists; in control environments, biomass was placed above abundance, suggesting these environments have a predominance of k-strategist species, as we suggested; and we observed increased levels of temperature favor the most abundant species, the ones having generalist biological mechanisms; however, contrary to what we expected, there was no difference in richness. With these results, we reinforce the need for public policies to create or maintain the riparian forest along streams running through urban areas and create or maintain urban parks.
Highlights
55% of the world’s population lives in urban areas, a proportion that might increase to 68% until 2050
Projections show that the gradual migration of the human population from rural to urban areas is congruent with the worldwide population growth, which could reach 2.5 billion until 2050 [1]
Species richness of Zygoptera was not affected by urbanization, contrary to what we expected evidence that, depending on the type of land use, the morphological characteristics of Odonata may better respond to the effects of environmental changes
Summary
55% of the world’s population lives in urban areas, a proportion that might increase to 68% until 2050. Increased population growth in urban areas causes significant losses in the world’s biodiversity [3,4]. Such damages can be more expressive in sensitive systems such as aquatic ecosystems, because they are strongly associated with the surrounding terrestrial vegetation. The loss of this vegetation can cause an increase in channel silting, homogenization of the substrate, water channeling and discharge of residential and/or industrial waste [5]
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