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Ignoring Non-English-Language Studies May Bias Ecological Meta-Analyses

Konno, K., Akasaka, M., Koshida, C., Katayama, N., Osada, N., Spake, R. and Amano, T. (2020) Ecology and Evolution.

By reanalysing existing meta-analyses including both English- and Japanese-language studies, we show that effect sizes differ significantly between English- and Japanese-language studies, causing considerable changes in overall mean effect sizes and even their direction when Japanese-language studies are excluded (see figure below). The differences in effect sizes are likely attributable to systematic differences in reported statistical results (language bias in statistical results – see diagram below) as well as study characteristics, particularly taxa and ecosystems (language bias in study characteristics), between English- and Japanese-language studies. This finding has a broad, yet simple implication: future meta-analyses—particularly those conducted at global extents or in regions where English is not widely spoken—should actively search for relevant non-English-language studies, and if appropriate, include them.

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Differences in mean effect sizes between English- (blue) and Japanese-language studies (red) included in existing ecological meta-analyses (left: Koshida & Katayama (2018) Conservation Biology, right: Osada et al. (2013) Japanese Journal of Ecology).

The fate of ignoring studies published in relevant language(s). Studies providing certain information may be more likely to be published in non-English languages (language bias in study characteristics) because, for example, those studies are often not of great interest from an international perspective. After the analysis, statistically significant or positive results may be more likely to be published in higher-impact, English-language journals (language bias in statistical results).

Languages are still a major barrier to global science

Amano, T., González-Varo, J.P. and Sutherland, W.J. (2016) PLOS Biology 14: e2000933.

This piece was our initial attempt to review how language barriers affect science in two directions: (i) when compiling knowledge globally and (ii) when applying knowledge to local environmental issues. For (i) we estimated that up to 36% of conservation-related scientific documents in 2014 were published in non-English languages (below). This clearly indicates an untapped potential of non-English-language literature as an important source of scientific knowledge. For (ii) our survey showed that 54% of protected area directors in Spain identified language as a barrier to the use of scientific papers for their management. At the end of this paper we also provide a number of suggestions for tackling this issue.

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Four barriers to the global understanding of biodiversity conservation: wealth, language, geographical location and security.

Amano, T. and Sutherland, W.J. (2013) Proceedings of the Royal Society B: Biological Science 280: 20122649.

In this paper we found that the availability of data stored in biodiversity databases is highly geographically biased (see figure below), and the proportion of English speakers in each country partly explains the distribution, with a fewer records per area stored for countries where English is not widely spoken. This indicates that language barriers could impede scientific activities and communications at the international level. This finding served as a basis for our endeavour to further investigate consequences of language barriers in science.

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The number of records per square kilometre in four conservation/ecological databases: (a) the Global Biodiversity Information Facility, (b) the Global Population Dynamics Database, (c) MoveBank and (d) the European Union for Bird Ringing Databank.