Planetary boundaries, tipping points and

Question

biodiversity
Even before trade-offs among ecosystem services and biodiversity
are considered, we may be able to identify critical thresholds — for
example, a quantitative value for a measure of biodiversity that we
do not want to fall below. This idea is the basis for what Rockström
et al. [33] call ‘a novel concept, planetary boundaries, for estimating
a safe operating space for humanity with respect to the functioning
of the Earth System’. They defined boundaries as ‘… humandetermined values of the control variable set at a ‘safe’ distance
from a dangerous level (for processes without known thresholds at
the continental to global scales) or from its global threshold.
Determining a safe distance involves normative judgments of how
societies choose to deal with risk and uncertainty’.
This approach has gained consideration in some post-2010
strategies. For example, the International Expert Workshop on the
2010 Biodiversity Indicators and Post-2010 Indicator Development
[8] concluded that: ‘Ecosystem tipping points and their possible
consequences for human well-being should be considered and
provide justification for targets and effective policy responses, on
the basis of the precautionary principle’.
Rockström et al. [33] suggested a tipping point for the number of
species extinctions, based simply on the argument that ‘massive loss
of biodiversity [is] unacceptable for ethical reasons’. How might
consideration of ecosystem services provide more defensible,
objective, inputs to this kind of approach? First, ecosystem service
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considerations suggest that tipping points based only on species
numbers may be questionable. From an ecosystem services
perspective, losing a given number of species belonging to the same
branch of the tree of life is not the same as losing the same number
of species belonging to different branches.
A simple example (Figure 2) illustrates the disconnect between the
number of species lost, and the proportion of evolutionary history
lost. Yesson and Culham [54] used a phylogenetic tree for a plant
group, Cyclamen, to examine PD losses under scenarios of climate
change. They found high phylogenetic dispersion of those Cyclamen
taxa with the lowest probability of extinction arising from potential
climate change impacts. This pattern implied that the potential loss
of PD and evolutionary potential through climate change was smaller
than might be expected based only on species-counting. As Figure 2a
shows, the six persisting, phylogenetically well-dispersed, Cyclamen
species retain a large amount of PD. But now imagine that the exact
same number of species persist, but are clumped in one part of the
tree. Figure 2b depicts these hypothetical situations and illustrates
that the loss of PD, for the same level of species loss, is much greater.
This disconnect between species numbers and ecosystem services
suggests that tipping points based on species counts may have little
utility. There is also a positive message — perhaps the most natural
manifestation of a tipping point can be found for these same
phylogenetic trees and ecosystem services. Tipping points may take
into account longstanding pressures, with delayed impacts on
biodiversity. Figure 3 provides a hypothetical illustration of what this
means for the loss of evolutionary history (PD), as extinctions
continue within a taxonomic group. The plot shows that successive
species extinctions each may imply only a moderate loss of PD, until,
abruptly, the last species goes extinct — and the long branch,
representing a large amount of PD, is lost. A nominated ‘boundary’
could reflect the degree of acceptable risk to ecosystem services
relative to this tipping point. An approach called ‘phylogenetic risk
analysis’ [55•] provides exactly this kind of risk assessment. For
instance, one can study ‘worst-case losses’ that arise when one or
more entire branches of the phylogenetic tree are lost. Phylogenetic
risk analysis can guide decisions that try to reduce risk of these
tipping point outcomes.
Currently, some authors are exploring boundaries and tipping points
for one group, corals that are particularly threatened by climate and
land use changes. Carpenter et al. [56] calculated that ‘32.8% of
zooxanthellate corals fall into threatened categories, compared to
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approximately 25% of mammals and 14% of birds…If Near
Threatened species are added, the proportion of corals (57.8%)
exceeds that of all terrestrial animal groups assessed to date.’. These
impacts on corals may be even greater at the phylogenetic level.
While vulnerabilities to environmental changes are well dispersed on
the phylogenetic tree (lots of diversity would persist), there are
many examples where entire clades fall into IUCN threatened (or
near-threatened) classes. On the basis of a large phylogenetic tree
for corals [57], we can identify several cases resembling our simple
example in Figure 3. For example, all listed species within
Catalaphyllia, Physogyra, and Euphyllia are assigned to one of the
threatened or near-threatened categories [56]. The phylogenetic
tree shows that these are the only descendents of a long branch.
Thus, we have a situation in corals where conservation decisions can
focus on the potential worst-case loss of this deeper branch (and the
corresponding loss of ecosystem services). Our conjecture is that
similar risks associated with phylogenetic tipping points will be found
in many lineages.
Conclusions
A core aspect of sustainability is the achievement of a good balance
among the different needs of society [23]. We have argued that
appreciation and quantification of ecosystem (as opposed to just
ecosystem) services can help ensure that biodiversity is properly
taken into account in trade-offs and decision-making.
We have not really addressed the important question of the
relationship between ecosystem services and ecosystem services. In
so far as all organisms and their features and interactions are
products of evolution, it might be argued that ecosystem services are
a subset of ecosystem services. Another perspective is that the idea
of ecosystem services helps us to appreciate that ecosystem services
have themselves changed over evolutionary time, as the
components of these systems have themselves evolved and
diversified. Our focus above has been on the use of the phrase
‘ecosystem services’ as a tool to help us better account for all (or at
least more) of the values associated with biodiversity. In this respect
we view ecosystem services and ecosystem services as
complementary. We think that the notion of ecosystem services can
help us to better appreciate and measure the services provided by
the tree of life and by healthy contemporary evolutionary systems.
But, regardless of the exact terminology we adopt, our main
argument is that we need fresh perspectives on biodiversity that
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help us to better represent the full range of uses and services in
decision-making for sustainability. We believe that the phrase
‘ecosystem services’ could prove useful in this context.
We close with a return to the discussion of prospects for a new CBD
Strategic Plan [8]: ‘The overarching goals of the Plan should be to
promote the health of ecosystems in the interest of human wellbeing, to reduce the risks to human well-being from biodiversity loss,
and to ensure options for future generations are maintained’ (see
also [58]). In this spirit, we have argued that human well-being is
adequately safeguarded only when we appreciate the way in which
it depends both on traditional ecosystem services and on the
ecosystem services that we have highlighted here. This perspective
simply amplifies the last segment of the quote — the ‘options for
future generations’ that evolution has provided, and will continue to
provide, are critical in fully appreciating nature's gifts to human wellbeing.
What is the link between this article and my field of study? [4 marks]
5) How is the content in this article relevant to the present day? [5 marks]
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6) How has the article increased my understanding of the issue being discussed? [5 marks]

Answer 1

1. What is the link between this article and my field of study? [4 marks]

The link between this article and your field of study depends on the specific area you are focused on; however, the themes discussed are broadly relevant across various fields such as environmental science, ecology, conservation biology, and sustainability studies. The concept of "planetary boundaries" and the exploration of biodiversity loss and tipping points are critical in these areas. If your field is related to environmental management, the article offers insights into how ecosystem services and biodiversity are interconnected, underlining the importance of sustainability in decision-making. Moreover, if you are involved in policy development, understanding tipping points and their implications for human well-being can be instrumental in creating effective environmental policies.

2. How is the content in this article relevant to the present day? [5 marks]

The content in this article is highly relevant to the present day due to ongoing global concerns regarding biodiversity loss, climate change, and ecosystem degradation. As countries and organizations strive to meet sustainability goals and radical environmental changes, the concept of planetary boundaries serves as a framework for assessing our environmental impact. The article reflects current challenges, such as the alarming rates of species extinction and the critical role of biodiversity in human well-being, driving home the importance of preserving ecosystem services. This insight is critical for contemporary discussions about policy formation, sustainable development, and international conservation efforts. Additionally, with the growing awareness of environmental crises, the article's emphasis on ecosystem services as a means to appreciate biodiversity’s value and inform decision-making resonates with calls for more integrated approaches to sustainability.

3. How has the article increased my understanding of the issue being discussed? [5 marks]

The article enhances understanding of the complex relationship between biodiversity, ecosystem services, and human well-being by introducing the concept of tipping points and the distinctions between species loss and evolutionary history loss. It highlights that not all species losses hold the same ecological significance, urging a more nuanced approach to evaluating biodiversity's decline. By incorporating the idea of phylogenetic risk analysis, the article illustrates how specific lineages may represent greater risks for ecosystem services, emphasizing the importance of understanding these connections in conservation efforts. This depth of analysis broadens the perspective on biodiversity beyond mere species counts, encouraging a more comprehensive understanding of ecological resilience and the long-term implications of biodiversity loss. Consequently, readers can appreciate the critical role of ecosystems in supporting human life and the need for informed, proactive measures in managing biodiversity for future sustainability.