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Impacts on ecosystems

[edit]
Large proposal moved here from Talk:Global warming

Present revision:


[...] Increased atmospheric CO2 increases the amount of CO2 dissolved in the oceans.[73] CO2 dissolved in the ocean reacts with water to form carbonic acid, resulting in ocean acidification. Ocean surface pH is estimated to have decreased from 8.25 near the beginning of the industrial era to 8.14 by 2004,[74] and is projected to decrease by a further 0.14 to 0.5 units by 2100 as the ocean absorbs more CO2.[3][75] Heat and carbon dioxide trapped in the oceans may still take hundreds of years to be re-emitted, even after greenhouse gas emissions are eventually reduced.[8] Since organisms and ecosystems are adapted to a narrow range of pH, this raises extinction concerns and disruptions in food webs.[76] One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.[77] However, few mechanistic studies have documented extinctions due to recent climate change,[78] and one study suggests that projected rates of extinction are uncertain.[79]


Compare with the IPCC Synthesis report [1]:


  • The resilience of many ecosystems is likely to be exceeded this century by an unprecedented combination of climate change, associated disturbances (e.g. flooding, drought, wildfire, insects, ocean acidification) and other global change drivers (e.g. land-use change, pollution, fragmentation of natural systems, over-exploitation of resources). {WGII 4.1-4.6, SPM}
  • Over the course of this century, net carbon uptake by terrestrial ecosystems is likely to peak before mid-century and then weaken or even reverse[16], thus amplifying climate change. {WGII 4.ES, Figure 4.2, SPM}
  • Approximately 20 to 30% of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5 to 2.5°C (medium confidence). {WGII 4.ES, Figure 4.2, SPM}
  • For increases in global average temperature exceeding 1.5 to 2.5°C and in concomitant atmospheric CO2 concentrations, there are projected to be major changes in ecosystem structure and function, species’ ecological interactions and shifts in species’ geographical ranges, with predominantly negative consequences for biodiversity and ecosystem goods and services, e.g. water and food supply. {WGII 4.4, Box TS.6, SPM}


Main differences

  • The article is biased towards certain topics
    • ocean acidification
    • projections of extinctions
    • uncertainty in these projections
  • Uncertainty is poorly treated

Article:


Since organisms and ecosystems are adapted to a narrow range of pH, this raises extinction concerns and disruptions in food webs.[76]


"raises extinction concerns" is vague. Table 19.1 of the IPCC Working Group II report states [2]:


Ocean acidification already occurring, increasing further as atmospheric CO2 concentration increases ***; ecological changes are potentially severe *


"ecological changes are potentially severe *" is given a confidence level (* = medium confidence). This is more useful than stating that ocean acidification "raises extinction concerns". The current sentence in the article could be replaced with (in bold):


[...] Increased atmospheric CO2 increases the amount of CO2 dissolved in the oceans.[73] CO2 dissolved in the ocean reacts with water to form carbonic acid, resulting in ocean acidification. Ocean surface pH is estimated to have decreased from 8.25 near the beginning of the industrial era to 8.14 by 2004,[74] and is projected to decrease by a further 0.14 to 0.5 units by 2100 as the ocean absorbs more CO2.[3][75] Heat and carbon dioxide trapped in the oceans may still take hundreds of years to be re-emitted, even after greenhouse gas emissions are eventually reduced.[8] Schneider and others (2007) concluded, with medium confidence, that ecological changes due to ocean acidification would potentially be severe. [...]


A shorter, less precise sentence is:


The ecological impacts of ocean acidification are potentially severe.


Article:


(i) One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.[77] (ii) However, few mechanistic studies have documented extinctions due to recent climate change,[78] and one study suggests that projected rates of extinction are uncertain.


Sentence (i) is similar to this bit in the Synthesis report:


  • Approximately 20 to 30% of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5 to 2.5°C (medium confidence). {WGII 4.ES, Figure 4.2, SPM}


Note that this is only given medium confidence, whereas other impacts are high confidence. I suggest that this sentence is deleted and replaced with something which has a higher level of confidence attached to it. The most obvious, and perhaps arbitrary thing to do, would be to refer to the first thing the Synthesis report states about ecosystems. This is:


  • The resilience of many ecosystems is likely to be exceeded this century by an unprecedented combination of climate change, associated disturbances (e.g. flooding, drought, wildfire, insects, ocean acidification) and other global change drivers (e.g. land-use change, pollution, fragmentation of natural systems, over-exploitation of resources). {WGII 4.1-4.6, SPM}


In this form, it is not very useful, so we can refer to the relevant chapter in the WGII report (chapter 4). From the executive summary (p. 213) [3]:


During the course of this century the resilience of many ecosystems (their ability to adapt naturally) is likely to be exceeded by an unprecedented combination of change in climate, associated disturbances (e.g., flooding, drought, wildfire, insects, ocean acidification) and in other global change drivers (especially land-use change, pollution and over-exploitation of resources), if greenhouse gas emissions and other changes continue at or above current rates (high confidence).

By 2100, ecosystems will be exposed to atmospheric CO2 levels substantially higher than in the past 650,000 years, and global temperatures at least among the highest of those experienced in the past 740,000 years (very high confidence) [4.2, 4.4.10, 4.4.11; Jansen et al., 2007]. This will alter the structure, reduce biodiversity and perturb functioning of most ecosystems, and compromise the services they currently provide (high confidence) [4.2, 4.4.1, 4.4.2-4.4.9, 4.4.10, 4.4.11, Figure 4.4, Table 4.1]. Present and future land-use change and associated landscape fragmentation are very likely to impede species’ migration and thus impair natural adaptation via geographical range shifts (very high confidence) [4.1.2, 4.2.2, 4.4.5, 4.4.10].


I think the best thing to take from this is this part:


By 2100, ecosystems will be exposed to atmospheric CO2 levels substantially higher than in the past 650,000 years, and global temperatures at least among the highest of those experienced in the past 740,000 years (very high confidence) [4.2, 4.4.10, 4.4.11; Jansen et al., 2007]. This will alter the structure, reduce biodiversity and perturb functioning of most ecosystems, and compromise the services they currently provide (high confidence)


This could be condensed down to:


Global warming is expected to result in reduced biodiversity of ecosystems.


Incorporated into the existing revision:


[...] Increased atmospheric CO2 increases the amount of CO2 dissolved in the oceans.[73] CO2 dissolved in the ocean reacts with water to form carbonic acid, resulting in ocean acidification. Ocean surface pH is estimated to have decreased from 8.25 near the beginning of the industrial era to 8.14 by 2004,[74] and is projected to decrease by a further 0.14 to 0.5 units by 2100 as the ocean absorbs more CO2.[3][75] Heat and carbon dioxide trapped in the oceans may still take hundreds of years to be re-emitted, even after greenhouse gas emissions are eventually reduced.[8] Since organisms and ecosystems are adapted to a narrow range of pH, this raises extinction concerns and disruptions in food webs.[76]

Global warming is expected to result in reduced biodiversity of ecosystems. Few mechanistic studies have documented extinctions due to recent climate change,[78] and one study suggests that projected rates of extinction are uncertain.[79]


I think this revision is preferable to the earlier one because the new sentence is based on a high confidence statement, rather than a statement of uncertain confidence.

Sentence (ii)


(i) One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.[77] (ii) However, few mechanistic studies have documented extinctions due to recent climate change,[78] and one study suggests that projected rates of extinction are uncertain.


Sentence (ii) can be broken down into two parts:


However, (a) few mechanistic studies have documented extinctions due to recent climate change,[78] and (b) one study suggests that projected rates of extinction are uncertain.


(a) is a comment on observed effects of climate change, (b) is a comment on extinction projections. Starting with (a), lets refer back to the IPCC Synthesis report [4]:


Observational evidence[4] from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases. {1.2}

Changes in snow, ice and frozen ground have with high confidence increased the number and size of glacial lakes, increased ground instability in mountain and other permafrost regions and led to changes in some Arctic and Antarctic ecosystems. {1.2}

There is high confidence that some hydrological systems have also been affected through increased runoff and earlier spring peak discharge in many glacier- and snow-fed rivers and through effects on thermal structure and water quality of warming rivers and lakes. {1.2}

In terrestrial ecosystems, earlier timing of spring events and poleward and upward shifts in plant and animal ranges are with very high confidence linked to recent warming. In some marine and freshwater systems, shifts in ranges and changes in algal, plankton and fish abundance are with high confidence associated with rising water temperatures, as well as related changes in ice cover, salinity, oxygen levels and circulation. {1.2}

Of the more than 29,000 observational data series, from 75 studies, that show significant change in many physical and biological systems, more than 89% are consistent with the direction of change expected as a response to warming (Figure SPM.2). However, there is a notable lack of geographic balance in data and literature on observed changes, with marked scarcity in developing countries.


As you can see, the IPCC Synthesis report cites evidence for observed impacts, yet the article only concentrates on observations in one particular area. I think this is biased. To correct this, I suggest that the highest confidence statement from the Synthesis report replaces part (a) of the sentence. The highest confidence statement made is:


In terrestrial ecosystems, earlier timing of spring events and poleward and upward shifts in plant and animal ranges are with very high confidence linked to recent warming.


My suggested revision is:


In terrestrial ecosystems, evidence for recent warming includes the earlier timing of spring events, and poleward and upward shifts in plant and animal ranges.


Incorporated into the existing article revision:


Additional anticipated effects include sea level rise of 0.18 to 0.59 meters (0.59 to 1.9 ft) in 2090–2100 relative to 1980–1999,[3] new trade routes resulting from arctic shrinkage,[67] possible thermohaline circulation slowing, increasingly intense, in some locations, (but less frequent) hurricanes [68]and extreme weather events,[69] reductions in the ozone layer, changes in agriculture yields, changes in the range of climate-dependent disease vectors,[70] which have been linked to increases in the prevalence of malaria and dengue fever,[71] and ocean oxygen depletion.[72] Increased atmospheric CO2 increases the amount of CO2 dissolved in the oceans.[73] CO2 dissolved in the ocean reacts with water to form carbonic acid, resulting in ocean acidification. Ocean surface pH is estimated to have decreased from 8.25 near the beginning of the industrial era to 8.14 by 2004,[74] and is projected to decrease by a further 0.14 to 0.5 units by 2100 as the ocean absorbs more CO2.[3][75] Heat and carbon dioxide trapped in the oceans may still take hundreds of years to be re-emitted, even after greenhouse gas emissions are eventually reduced.[8] Since organisms and ecosystems are adapted to a narrow range of pH, this raises extinction concerns and disruptions in food webs.[76]

In terrestrial ecosystems, evidence for recent warming includes the earlier timing of spring events, and poleward and upward shifts in plant and animal ranges. One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.[77] One study suggests that projected rates of extinction are uncertain.[79]


I think this revision is an improvement on the previous revision because it is not biased towards non-detection of climate change, and it is a based on a finding the IPCC made with very high confidence.

Part (b) of the sentence:


However, (a) few mechanistic studies have documented extinctions due to recent climate change,[78] and (b) one study suggests that projected rates of extinction are uncertain.


Referring back to the IPCC Synthesis report, it does not mention "projected rates of extinction". Therefore I think mention of this is biased. Part (b) is also vague. It states that:


projected rates of extinction are uncertain.


This is meaningless without specifying what the nature of the uncertainty is. To conclude:

  • The choice of subject for part (b) of the sentence is arbitrary. The fact that it is not mentioned in the IPCC Synthesis report makes me think that it is relatively unimportant compared to other topics regarding ecosystems.
  • It is vague, perhaps to the point of being meaningless

Replacement

If we have to have something on projections of ecosystem extinctions, it would make sense for the magnitude of extinction plus the uncertainty of the projection to stated. I think magnitude of extinction is more important than the rate of extinction since the IPCC Synthesis report mentions a magnitude estimate:


  • Approximately 20 to 30% of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5 to 2.5°C (medium confidence). {WGII 4.ES, Figure 4.2, SPM}


This also has a confidence level attached to it. In the existing revision, we already have a magnitude estimate of extinctions:


(i) One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.[77] (ii) However, few mechanistic studies have documented extinctions due to recent climate change,[78] and one study suggests that projected rates of extinction are uncertain.


No confidence level is attached to the projection, but he Synthesis report includes a confidence level.

Suggested change

For this, I think it's helpful to look at the IPCC report chapter the Synthesis report is referring to (Chapter 4, WGII):


Approximately 20 to 30% of plant and animal species assessed so far (in an unbiased sample) are likely to be at increasingly high risk of extinction as global mean temperatures exceed a warming of 2 to 3°C above preindustrial levels (medium confidence) [4.4.10, 4.4.11, Figure 4.4, Table 4.1].

Projected impacts on biodiversity are significant and of key relevance, since global losses in biodiversity are irreversible (very high confidence) [4.4.10, 4.4.11, Figure 4.4, Table 4.1]. Endemic species richness is highest where regional palaeoclimatic changes have been muted, providing circumstantial evidence of their vulnerability to projected climate change (medium confidence) [4.2.1]. With global average temperature changes of 2°C above pre-industrial levels, many terrestrial, freshwater and marine species (particularly endemics across the globe) are at a far greater risk of extinction than in the recent geological past (medium confidence) [4.4.5, 4.4.11, Figure 4.4, Table 4.1]. Globally about 20% to 30% of species (global uncertainty range from 10% to 40%, but varying among regional biota from as low as 1% to as high as 80%) will be at increasingly high risk of extinction, possibly by 2100, as global mean temperatures exceed 2 to 3°C above pre-industrial levels [4.2, 4.4.10, 4.4.11, Figure 4.4, Table 4.1]. Current conservation practices are generally poorly prepared to adapt to this level of change, and effective adaptation responses are likely to be costly to implement (high confidence) [4.4.11, Table 4.1, 4.6.1].


My suggested revision is:


If global mean temperatures exceed 2 to 3°C above pre-industrial levels, around 20 to 30% of species might be at increased risk of extinction, possibly by 2100.


In many ways, this is an unsatisfactory revision. It is less specific than the IPCC report, but it's the best I can do without writing another few sentences. I chose to say "might be at increased risk of extinction" because the IPCC report only has medium confidence in the projection. Additionally, my sentence does not actually refer to the fact that the figure is derived from the "species assessed so far". The fact that Fischlin et al. mentioned this is no doubt significant. So by using the word "might", I hope to give some indication of the uncertainties surrounding this projection.

Here is this new revision integrated into the existing revision:


Additional anticipated effects include sea level rise of 0.18 to 0.59 meters (0.59 to 1.9 ft) in 2090–2100 relative to 1980–1999,[3] new trade routes resulting from arctic shrinkage,[67] possible thermohaline circulation slowing, increasingly intense, in some locations, (but less frequent) hurricanes [68]and extreme weather events,[69] reductions in the ozone layer, changes in agriculture yields, changes in the range of climate-dependent disease vectors,[70] which have been linked to increases in the prevalence of malaria and dengue fever,[71] and ocean oxygen depletion.[72] Increased atmospheric CO2 increases the amount of CO2 dissolved in the oceans.[73] CO2 dissolved in the ocean reacts with water to form carbonic acid, resulting in ocean acidification. Ocean surface pH is estimated to have decreased from 8.25 near the beginning of the industrial era to 8.14 by 2004,[74] and is projected to decrease by a further 0.14 to 0.5 units by 2100 as the ocean absorbs more CO2.[3][75] Heat and carbon dioxide trapped in the oceans may still take hundreds of years to be re-emitted, even after greenhouse gas emissions are eventually reduced.[8] Since organisms and ecosystems are adapted to a narrow range of pH, this raises extinction concerns and disruptions in food webs.[76]

If global mean temperatures exceed 2 to 3°C above pre-industrial levels, around 20 to 30% of species might be at increased risk of extinction, possibly by 2100. However, few mechanistic studies have documented extinctions due to recent climate change,[78] and one study suggests that projected rates of extinction are uncertain.[79]


As you can see, it's a swap of the previous sentence with my new one:

Old


(i) One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.[77]


New


If global mean temperatures exceed 2 to 3°C above pre-industrial levels, around 20 to 30% of species might be at increased risk of extinction, possibly by 2100.


  • I think that it is better to use the IPCC report instead of an individual paper
  • It is a more important projection – it applies to all species rather than just the sample in the cited study.
  • It specifically relates impacts to global mean temperature
  • It gives some impression of projection uncertainty.

Further comment on sentences (i) and (ii)


(i) One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.[77] (ii) However, (I) few mechanistic studies have documented extinctions due to recent climate change,[78] and (II) one study suggests that projected rates of extinction are uncertain.


The word "however" links sentence (i) to sentence (ii). This implies that subject (I) has an affect on the study in sentence (i). Subject (I) has to do with attributing observed extinctions to climate change. Sentence (i) is about future extinctions. The linking of the two sentences with the word "however" suggests that subject (I) has a negative bearing on the validity of the previous sentence.

To see if this is the case, it is worth checking the study referred to in sentence (i). This is a study by Thomas et al (2004) pdf. Referring to the later section of the paper on uncertainties in projections:


Many unknowns remain in projecting extinctions, and the values provided here should not be taken as precise predictions. Analyses need to be repeated for larger samples of regions and taxa, and the selection of climate change scenarios need to be standardized. Some of the most important uncertainties follow (see also Supplementary Information). We estimate proportions of species committed to future extinction as a consequence of climate change over the next 50 years, not the number of species that will become extinct during this period. Information is not currently available on time lags between climate change and species-level extinctions, but decades might elapse between area reduction (from habitat loss) and extinction14. Land use should also be incorporated into analyses: extinction risks might be higher than we project if future locations of suitable climate do not coincide with other essential resources (such as soil type or food resources). There is also uncertainty over which species will inhabit parts of the world projected to have climates for which no current analogue exists6. Equally importantly, all parts of the world will have historically unprecedented CO2 levels6, which will affect plant species and ecosystems21,22 and herbivores23, resulting in novel species assemblages and interactions.


No reference is made to observed extinctions attributed to climate change affecting uncertainty of their projections. Therefore it's worth looking at the source provided to support subject (I). The link to this reference was dead so I've updated it. It refers to a paper by McLaughlin et al (2002). If subject (I) is related to the projection in sentence (i), it should be in this reference. To recap, subject (I) is:


"few mechanistic studies have documented extinctions due to recent climate change"


and was linked to the previous sentence on projections by the word "however". From McLaughlin et al (2002) [5]:


Climate change at global and regional scales is predicted to alter species distributions, life histories, community composition, and ecosystem function (1–5). In particular, population losses caused by climate change threaten both species diversity and the delivery of critical ecosystem services (6). Predictions of climate-induced population extinctions are supported by correlational evidence that numerous species are shifting their ranges in response to climatic warming (7–11). Nevertheless, few mechanistic studies have linked extinctions to recent climate change (12, 13). Furthermore, most climate change research and forecasts focus on shifts in climatic means. Global climate models also predict changes in climatic variability (14, 15), but biotic impacts of those increases have received less study. Here, we report that extinctions of two populations of the checkerspot butterfly, Euphydryas editha bayensis, were caused by a combination of habitat loss and regional climate change in the form of increasing variability in precipitation.


Checking references 12 and 13 does not show the Thomas et al (2004), which is not surprising since McLaughlin et al (2002) is an earlier paper. In my view, the choice of another editor to synthesize sentence (i) with subject (I) is probably acceptable, but I don't think that it's ideal. It would be better to simply restructure sentences (i) and (ii). My suggested change is:


(1) Few mechanistic studies have linked extinctions to recent climate change. (2) One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections. (3) Another study suggests that projected rates of extinction are uncertain.


This avoids the problem of synthesizing the two studies. I should note that as I described earlier, sentences (2) and (3) are problematic. In particular, the third sentence here is weak. It would be better to simply refer to the uncertainties as described by Thomas et al (2004) in their projections, rather than referring to another paper. You can see that this revision still suffers from a synthesis problem with sentences two and three. Sentence three could be interpreted as a negative comment on the validity of the previous sentence. Sentence (3) is poor. It does not specify any comment on the nature of uncertainties in projections.

Subject (II)

To recap:


(i) One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.[77] (ii) However, (I) few mechanistic studies have documented extinctions due to recent climate change,[78] and (II) one study suggests that projected rates of extinction are uncertain.


In a similar fashion to subject (I), subject (II) could also be read as a negative comment on the validity of sentence (i). It could therefore also suffer from the problem of improper synthesis. Subject (II) is based on a paper by Botkin et al (2007) pdf. It refers to the Thomas et al. (2004) and does describe areas of uncertainty in this paper. Its inclusion is therefore valid. Still, I would prefer it if the "however" link is removed.

Thomas et al (2004) do comment on uncertainties in their projections. The editor who structured sentences (i) and (ii) did attempt to covey they uncertainties over these projections. I think there's room for improvement:


(1) Few mechanistic studies have documented extinctions due to recent climate change. (2) One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections. (3) These types of studies do, however, have limitations.


This revision I think is more logical. It preserves the chronological order of the papers. It is also logical in the sense that observations are first commented on, followed by projections of future changes, followed by a comment on projections. Despite this, I think that this is still a weak improvement.

Sentence (3):


These types of studies do, however, have limitations.


is I feel a very minor improvement on:


[...] one study suggests that projected rates of extinction are uncertain.


Sentence (3) is based on the abstract of the paper by Botkin et al (2007), where it is stated that:


The demand for accurate forecasting of the effects of global warming on biodiversity is growing, but current methods for forecasting have limitations.


Summary

Overall I think that reference to the papers by McLaughlin et al (2002), Thomas et al (2004), and Botkin et al (2007) is not justified. The article at present is biased towards ecosystem projections and non-attribution of ecosystem impacts (extinctions). References to the stated papers, in my view, is not justified. Selection appears to be arbitrary and the failure to refer to the literature assessment by Fischlin et al (2007) is not acceptable. The choice made by editors of the article to focus on attribution of extinctions and projections of extinctions is biased because:

  • non-attribution is not as noteworthy as attribution.
  • The section is biased towards non-attribution, e.g., the literature assessment by Rosenzweig et al. (2007) is not mentioned [6]. This also applies to physical attribution [7].

Overall, the section's coverage of attribution studies is poor, and that applies to the area of ecosystems. Uncertainty is treated very poorly. Enescot (talk) 00:00, 17 March 2010 (UTC)[reply]

IMO, most or all of the suggested additions in the lengthy sections here and further above are perhaps better suited for consideration at Effects_of_global_warming. Please see also WP:Summary style and the essay WP:TLDR. I have no objection to trying some of the suggested condensations of points that arguably are too detailed or wordy at present. On a quick reading of the above, I think the suggested changes of wording are largely unnecessary. Of course there's always room for further improvements to articles. Why not take it one point at a time and see what the response is from the many editors who pitch in on this article?. ... Kenosis (talk) 19:10, 18 March 2010 (UTC)[reply]
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