At Home in Nature

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The effect of climate change on trees

In their Consequences of climate change on the tree of life in Europe (24 February 2011, VOL 470 NATURE pg 531), the Doctors Wilfried Thuiller, Sebastien Lavergne, Cristina Roquet, Isabelle Boulangeat, Bruno Lafourcade & Miguel. B. Araujo report that climate change will effect some species of trees more than others, resulting in dramatic changes to the ecology as ecosystems become redefined by different trees. “Reductions in phylogenetic diversity will be greater in southern Europe, and gains are expected in regions of high latitude or altitude. However, losses will not be offset by gains and the tree of life faces a trend towards homogenization across the continent.” The Doctors say that “Climatic tolerances vary across species, causing some species to be more vulnerable to climate change than others. Because climate tolerances are not randomly distributed across phylogenies, species sensitivities to climate change are expected to be clustered along the phylogeny. It follows that if vulnerable species are closely related, shared internal branches of the tree of life have higher risks of collapsing.” Their estimates for changes in phylogenetic diversity versus scenarios of random extinction for plants, birds and mammals (graphs, above) demonstrate 2 scenarios: a, Emission scenario A1F1; b, emission scenario B1. The grey area is the quantile range of projected phylogenetic diversity due to range contraction (from 2020 onward), randomly scattered across the sample of trees.

Difference between climate change and global warming

Ana Villar and Jon A. Krosnick in their recent publication, Global warming vs. climate change, taxes vs. prices: Does word choice matter? (Climatic Change (2011) 105:1–12) found that how we describe things does matter.  Their excellently worded abstract puts the situation succinctly, or should I say precisely? 


Does “climate change” seem like a less serious problem than “global warming” to Americans and Europeans? Does describing the costs of climate change mitigation in terms of “higher taxes” instead of “higher prices” reduce public support for such efforts? In an experiment embedded in an American national survey, respondents were randomly assigned to rate the seriousness of “global warming,” “climate change,” or “global climate change.” Contrary to predictions made by a leading political strategist, the full sample and political Independents perceived “climate change” and “global warming” to be equally serious. Among Republicans, “climate change” was perceived to be more serious than “global warming,” whereas the reverse was true among Democrats. A similar experiment embedded in a survey of residents of 31 European countries showed that “global warming” and “climate change” were perceived to be equally serious problems. And an experiment embedded in an American survey showed that describing the increased costs of climate change mitigation legislation via “higher taxes” instead of via “higher prices” did not reduce popular support for such legislation, also contradicting a political strategy memo. Thus, word choice may sometimes affect public perceptions of the climate change seriousness or support for mitigation policies, but a single choice of terminology may not influence all people the same way, making strategic language choices difficult to implement.


Yet words mean more to those who are more educated, especially in the phrasing of questions.  The doctors found that people with less education look to questioners and other people to form an ideology about a word: “among respondents with some college or less education, the primacy effect was sizable. The proportion of people who rated the problem as extremely serious or very serious when those options were presented first was 62.49%, compared to 55.89% when those options were last, a difference of 6.60% (?2 (1) = 9.04, p = 0.003, N = 2,005). Among respondents with a college degree or more education, the primacy effect was non-significant. The proportion of people who rated the problem as extremely serious or very serious when those options were presented first was 59.40%, compared to 58.14% when those options were last, a difference of 1.26% (?2 (1) = 0.14, p = 0.71, N = 861). Consistent with past research (e.g., Krosnick and Schuman 1988), education was a marginally significant moderator of the relation between response choice order and seriousness ratings (Wald (1) = 13.36, p = 0.09,one-tailed)… The primacy effect that appeared here was the same effect documented in many other past studies of rating scales and appeared here, as in past research, to be most common among people most likely to satisfice when answering survey questions: respondents low in education. It is therefore important to counter-balance rating scale point order in surveys in order to avoid bias.” 

Educated people have already formed opinions and ideology, which impacts the way that we interpret words: “Among Europeans in the “center,” people were equally likely to mention global warming as the most serious problem as they were to mention climate change (63.30% vs. 64.88%; ?2 (1) = 2.47, p = 0.12.)” 

Word choice matters, but no less so to those who are undeducated about a subject.  When using words, it is important to choose the most objective word, and to fully understand the word’s ideological associations with the audience at hand.

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