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Understanding environmental change through the lens of trait-based,
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functional and phylogenetic biodiversity in freshwater ecosystems
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Janne Alahuhta
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*, Tibor Erős
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, Olli-Matti Kärnä
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, Janne Soininen
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, Jianjung Wang
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, Jani Heino
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1 Geography Research Unit, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland
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2 Balaton Limnological Institute, MTA Centre for Ecological Research, Tihany, Hungary
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3 Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, FI-00014
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Helsinki, Finland
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4 Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73, East Beijing
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Road, 210008 Nanjing, China
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5 University of Chinese Academy of Sciences, 380 Huaibeizhuang, Huairou, 101408 Beijing, China
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6 Finnish Environment Institute, Biodiversity Centre, Paavo Havaksen tie 3, FI-90530 Oulu, Finland
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* Janne Alahuhta, Geography Research Unit, University of Oulu, P.O. Box 3000, 90014 Oulu,
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Finland. Email: janne.alahuhta@oulu.fi, Fax: +358 8 344 084
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Running head: Environmental change and freshwater biodiversity
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Paper type: Research Review
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Abstract
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In the era of the Anthropocene, environmental change is accelerating biodiversity loss across
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ecosystems on Earth, among which freshwaters are likely the most threatened. Different biodiversity
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facets in the freshwater realm suffer from various environmental changes that jeopardize the
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ecosystem functions and services important for humankind. In this work, we examine how
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environmental changes (e.g. climate change, eutrophication or invasive species) affect trait-based,
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functional and phylogenetic diversity of biological communities. We first developed a simple
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conceptual model of the possible relationships between environmental change and these three
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diversity facets in freshwaters, and secondly, systematically reviewed articles where these
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relationships had been investigated in different freshwater ecosystems. Finally, we highlighted
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research gaps from the perspectives of organisms, ecosystems, stressors and geographical locations.
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Our conceptual model suggested that both natural factors and global change operating at various
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spatial scales influence freshwater community structure and ecosystem functioning. The relationships
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between biodiversity and environmental change depend on geographical region, organism group,
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spatial scale and environmental change gradient length. The systematic review revealed that
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environmental change impacts biodiversity patterns in freshwaters, but there is no single type of
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biodiversity response to the observed global changes. Natural stressors had different, even
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contradictory effects (i.e., multiple, negative and positive) on biodiversity compared with
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anthropogenic stressors. Anthropogenic stressors more often decreased biodiversity, although
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eutrophication and climate change affected freshwater ecosystems in a complex, more
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multidimensional way. The research gaps we identified were related, for example, to the low number
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of community-based biodiversity studies, the lack of information on true phylogenies for all
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freshwater organism groups, the missing evaluations whether species traits are phylogenetically
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conserved, and the geographical biases in research (i.e., absence of studies from Africa, Southern
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Asia and Russia). We hope that our review will stimulate more research on the less well-known facets
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and topics of biodiversity loss in highly vulnerable freshwater ecosystems.
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Keywords: Community ecology, Diversity index, Functional diversity, Global change, Lakes,
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Phylogenetic diversity, Rivers, Species traits, Streams
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Introduction
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Environmental change affects biodiversity, but its influence varies in time and space, including within
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and across ecosystems (Hooper et al. 2012; Dornelas et al. 2014). In the era of the Anthropocene, the
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general understanding is that biodiversity loss is accelerating, for example, due to increased
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atmospheric greenhouse gases, land use alteration, environmental pollution including eutrophication,
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overexploitation of species and invasion of exotic species (McGill et al. 2015; Maxwell et al. 2016).
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Such undesirable progress affecting biodiversity is also jeopardizing ecosystem functions and
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services vital to human well-being (Cardinale et al. 2012). In this sense, perhaps the most threatened
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ecosystems exposed to environmental changes are freshwaters (Dudgeon et al. 2006; Vörösmarty et
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al. 2010; Wiens 2016; Vilmi et al. 2017). This is because many freshwater species have limited ability
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to disperse in the face of changing environmental conditions (Heino et al. 2009) and they are subject
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to multiple anthropogenic pressures acting simultaneously (Woodward et al. 2011). In addition,
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freshwaters are not often part of the biodiversity conservation programs.
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Although freshwaters account for only ca. 1% of the Earth’s total surface area, they are especially
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important ecosystems, because they 1) are hosting relatively larger proportion of biodiversity
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compared to terrestrial systems and 2) constitute a source for many of the essential but threatened
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ecosystem services, such as drinking water supplies, aquaculture and climate change mitigation
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(Dudgeon et al. 2006; Cardinale et al. 2012). In addition, freshwater and terrestrial ecosystems are
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fundamentally interrelated through the movement of energy, nutrients and other materials (Soininen
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et al. 2015). For example, organic matter within a catchment area and terrestrial organisms enter lentic
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and lotic systems, whereas aquatic insects emerge and fly to surrounding riparian zones, where they
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are eaten by terrestrial predators. Thus, freshwater ecosystems depend on multiple environmental
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characteristics operating at various spatial scales (Fig. 1). These issues not only highlight the
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importance to maintain and protect the taxonomic diversity of ecological communities, but also other
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facets of biodiversity in the freshwater realm at various spatial scales.
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Fig. 1. Conceptual illustration of the relationships between environmental change and freshwater
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community structure and ecosystem functioning. Freshwater (abiotic) ecosystem status is influenced
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by different environmental variables, ranging in an increasing order of importance from regional
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climate and catchment features to local environmental features. Ecological status of surface waters
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per se comprises of many water quality variables such as nutrient status and oxygen levels.
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