169
of sampling a dominant species with specific traits or a set of
species with complementary traits (Loreau and Hector 2001;
Fargione et al. 2007). In light of these mechanisms, most of
the empirical research developed in the last 10 years focused
on disentangling the relative contribution of community
composition (i.e., role of the taxonomic and/or functional
identity of species) and complementarity to the effect of biodiversity on ecosystem processes. Cardinale et al. (2012)
estimated an even contribution of both mechanisms, but
highlighted that available evidence is still fragmentary for
solving this debate.
Functional Diversity Determines Ecosystem Processes
and Services Changes in biodiversity at all levels of biological organization could affect, to a greater or lesser extent,
the functioning of ecosystems (e.g., Reusch et al. 2005;
Worm et al. 2006). Nevertheless, there is a general agreement that functional diversity is the dimension of biodiversity that contributes the most to the determination of
ecosystem processes (Díaz and Cabido 2001). Traits determine how species capture and use different resources, and
interact with the environment. Thus, the role of species in the
flux of energy and cycling of matter is shaped by their traits,
being the identity, abundance, and range of these traits what
links species and ecosystems from a functional perspective
(Fig. 1; Naeem 1996; Bengtsson 1998). The goods and services provided by ecosystems depend on the persistence of
biogeochemical processes, which rely on functional groups
(i.e., sets of species that exhibit certain functional traits). It is
the loss of functional groups, beyond species,
5
that compromises the capacity of ecosystems to continue providing benefits to humanity (Díaz et al. 2006). During mass extinctions,
and the current one is not the exception, the loss of species is
driven by negative selection against certain traits. Thus, identifying traits that determine a greater extinction risk, and how
they directly or indirectly (through the correlation with other
traits) influence ecosystem processes, is essential to predict
the consequences of extinctions on ecosystem services
(Cardinale et al. 2012, Fig. 1).
The information gathered so far has certainly been valuable for describing the effects that biodiversity has on ecosystem functioning (among other ecosystem characteristics)
and elucidating the underlying mechanisms that mediate
these effects. Nevertheless, a scale discrepancy still persists
5 It is important to clarify that keystone species (i.e., species with a disproportionately effect on the functioning of the ecosystem in comparison to its abundance) can be considered as single-species functional
groups, since they are fully non-redundant and non-replaceable (Bond
1994).
between the local nature of the evidence on which the current
understanding of the biodiversity-functioning relationship is
held and the global scale at which the impacts of anthropogenic activities on biodiversity have usually been described
(Isbell et al. 2017). The understanding of the potential cascading effects that large-scale changes in biodiversity might
have on ecosystems at a local scale is a challenge that still
needs to be addressed. In general, data have been generated
in a fragmented way at different spatial, temporal and ecological scales. In addition, there are almost no attempts in the
literature to integrate this knowledge (but see Isbell et al.
2017 for an example with a management background). In a
context where current methodological constraints prevent
“multi-scale” observational and experimental analyses of
certain phenomena and processes, theoretical essays and
modeling provide a powerful approach to bridge isolated
empirical efforts. Thus, constructing on the existing bibliography, this chapter will give an integrated perspective of the
impacts that global change drivers will have at different ecological scales — from regional species pools to the interaction between species in local communities — and their
potential consequences on the functioning of ecosystems
(Fig. 1). Beyond the literature review, we introduce a set of
tools which allow a holistic analysis of the consequences that
changes in biodiversity have on ecosystem processes under
global change.
Regional Pools of Species Under Global
Change: Is Biodiversity Decreasing?
Regional species pools are defined as the overall set of species that can colonize local communities.
6
The total number
of species observed in these pools is the result of the balance
between processes that increase (i.e., speciation and immigration) and decrease (i.e., extinction) species diversity
(Cornell and Harrison 2014). Human activities have heavily
altered these processes mainly by increasing the rates of
extinction and immigration. On one hand, the overexploitation of species of economic interest, the rapid and in many
cases irreversible loss of habitat and the reduction of distributional ranges due to changes in prevailing climatic conditions are responsible for the loss of species at a regional
scale. On the other hand, the dissemination of species out of
their native range has promoted the exchange of species
among previously isolated regions and in consequence the
introduction of exotic species (Sax and Gaines 2003). The
arrival and establishment of new species could have two
6 Recent reviews and perspective articles have extensively discussed the
regional species pool concept. We recommend Carstensen et al. (2013)
and Cornell and Harrison (2014) for an overview on the topic.
Biodiversity and the Functioning of Ecosystems in the Age of Global Change: Integrating Knowledge Across Scales
of sampling a dominant species with specific traits or a set of
species with complementary traits (Loreau and Hector 2001;
Fargione et al. 2007). In light of these mechanisms, most of
the empirical research developed in the last 10 years focused
on disentangling the relative contribution of community
composition (i.e., role of the taxonomic and/or functional
identity of species) and complementarity to the effect of biodiversity on ecosystem processes. Cardinale et al. (2012)
estimated an even contribution of both mechanisms, but
highlighted that available evidence is still fragmentary for
solving this debate.
Functional Diversity Determines Ecosystem Processes
and Services Changes in biodiversity at all levels of biological organization could affect, to a greater or lesser extent,
the functioning of ecosystems (e.g., Reusch et al. 2005;
Worm et al. 2006). Nevertheless, there is a general agreement that functional diversity is the dimension of biodiversity that contributes the most to the determination of
ecosystem processes (Díaz and Cabido 2001). Traits determine how species capture and use different resources, and
interact with the environment. Thus, the role of species in the
flux of energy and cycling of matter is shaped by their traits,
being the identity, abundance, and range of these traits what
links species and ecosystems from a functional perspective
(Fig. 1; Naeem 1996; Bengtsson 1998). The goods and services provided by ecosystems depend on the persistence of
biogeochemical processes, which rely on functional groups
(i.e., sets of species that exhibit certain functional traits). It is
the loss of functional groups, beyond species,
5
that compromises the capacity of ecosystems to continue providing benefits to humanity (Díaz et al. 2006). During mass extinctions,
and the current one is not the exception, the loss of species is
driven by negative selection against certain traits. Thus, identifying traits that determine a greater extinction risk, and how
they directly or indirectly (through the correlation with other
traits) influence ecosystem processes, is essential to predict
the consequences of extinctions on ecosystem services
(Cardinale et al. 2012, Fig. 1).
The information gathered so far has certainly been valuable for describing the effects that biodiversity has on ecosystem functioning (among other ecosystem characteristics)
and elucidating the underlying mechanisms that mediate
these effects. Nevertheless, a scale discrepancy still persists
5 It is important to clarify that keystone species (i.e., species with a disproportionately effect on the functioning of the ecosystem in comparison to its abundance) can be considered as single-species functional
groups, since they are fully non-redundant and non-replaceable (Bond
1994).
between the local nature of the evidence on which the current
understanding of the biodiversity-functioning relationship is
held and the global scale at which the impacts of anthropogenic activities on biodiversity have usually been described
(Isbell et al. 2017). The understanding of the potential cascading effects that large-scale changes in biodiversity might
have on ecosystems at a local scale is a challenge that still
needs to be addressed. In general, data have been generated
in a fragmented way at different spatial, temporal and ecological scales. In addition, there are almost no attempts in the
literature to integrate this knowledge (but see Isbell et al.
2017 for an example with a management background). In a
context where current methodological constraints prevent
“multi-scale” observational and experimental analyses of
certain phenomena and processes, theoretical essays and
modeling provide a powerful approach to bridge isolated
empirical efforts. Thus, constructing on the existing bibliography, this chapter will give an integrated perspective of the
impacts that global change drivers will have at different ecological scales — from regional species pools to the interaction between species in local communities — and their
potential consequences on the functioning of ecosystems
(Fig. 1). Beyond the literature review, we introduce a set of
tools which allow a holistic analysis of the consequences that
changes in biodiversity have on ecosystem processes under
global change.
Regional Pools of Species Under Global
Change: Is Biodiversity Decreasing?
Regional species pools are defined as the overall set of species that can colonize local communities.
6
The total number
of species observed in these pools is the result of the balance
between processes that increase (i.e., speciation and immigration) and decrease (i.e., extinction) species diversity
(Cornell and Harrison 2014). Human activities have heavily
altered these processes mainly by increasing the rates of
extinction and immigration. On one hand, the overexploitation of species of economic interest, the rapid and in many
cases irreversible loss of habitat and the reduction of distributional ranges due to changes in prevailing climatic conditions are responsible for the loss of species at a regional
scale. On the other hand, the dissemination of species out of
their native range has promoted the exchange of species
among previously isolated regions and in consequence the
introduction of exotic species (Sax and Gaines 2003). The
arrival and establishment of new species could have two
6 Recent reviews and perspective articles have extensively discussed the
regional species pool concept. We recommend Carstensen et al. (2013)
and Cornell and Harrison (2014) for an overview on the topic.
Biodiversity and the Functioning of Ecosystems in the Age of Global Change: Integrating Knowledge Across Scales