Wetlands of the South American Pacific Coast: A Bibliometric Approach


 Wetlands are ecosystems susceptible to anthropogenic impacts; analysis of the scientific publications on these ecosystems can be used as a reference for the adopting of measures to facilitate research and conservation. This bibliometric analysis aimed to evaluate the temporal evolution of scientific publications and trends in research topics related to the wetlands of Ecuador, Peru, and Chile; this region includes an extended desertic region in the southern Pacific. A total of 411 articles published during the period from 2000 to 2019 were reviewed. The most frequent subject areas were 'birds' and 'other types of fauna' (20.7% and 19.2%, respectively); the diversity of publications was similar, but the proportions of the total subject areas for each country varied. The number of papers published per year was found to be increasing. The thematic areas related to these ecosystems that require strengthening in Ecuador, Peru and Chile are identified (e. g. 'hydrology and sediment' in Peru, 'microscopic organisms' in Chile, and 'birds' in Ecuador). Decision-makers should use this information to promote the development of the lines of research identified for each country.


Introduction
Wetlands are highly productive ecosystems, where water is the main controlling factor of the environment and the lives of organisms (Ramsar Convention Secretariat 2013). They provide essential ecosystem services (Ghermandi et  One way to better understand the situation of these ecosystems is through bibliometric analysis of scienti c publications. Through such analysis, functional aspects for management can be recognized; for example, they allow us to identify research gaps and make correct use of research-oriented budgets and contrast the impact of such studies on society (Ellegaard and Wallin 2015; Song and Zhao 2013;Vanti 2000). At the same time, through this type of study it is possible to identify trends in research on speci c elds of knowledge, this being one of the main goals of the bibliometric approach (Romanelli et al. 2018;Wang et al. 2014). Also, bibliometrics reveals exciting perspectives on an analyzed topic, allowing us to identify any shortcomings (Corrales-Reyes and Dorta-Contreras 2019). All these aspects can generate a new outlook in little-explored elds of science and, in addition, serve as a guide for recently initiated researchers (Ellegaard and Wallin 2015; Zhang et al. 2010).
Around the world, most bibliometric analyses in wetlands have focused on the characteristics of trends based on the most frequently cited articles, scienti c journals, institutions, and the most productive countries, all without distinguishing the type of wetland (Ma et al. 2013;Zhang et al. 2010), while others have explored distribution according to thematic and territorial scope (Paracuellos and Ortega 2003; Wang et al. 2012). Bibliometric evaluations that have distinguished the type of wetland have focused on studying arti cial wetlands (Zhi and Ji 2012;Colares et al. 2020). Studies of this type do not exist within the South American continent. In this region, wetlands form a corridor of diversity that involves an entire desert region between Peru and Chile but continues to a more rainy region in Ecuador. The conducting of a bibliometric evaluation at the South Paci c level gives decision-makers the tools to enable them to identify trends and information gaps related to the coastal wetlands of the region. Therefore, the aim of this study was to evaluate the scienti c literature related to the coastal wetlands of the South Paci c in the last 20 years. At the same time, this paper aims to identify the predominant research topics associated with the study of these ecosystems in the region.

Article categorization
The literature was categorized based on three variables: (1) year of publication, (2) country where the study was conducted, and (3) thematic area, such as the discipline within which the work was carried out.
The thematic areas were determined according to the variety of wetland research centers in the region (Salazar-Navarro et al. 2020). The articles were categorized according to a) pathology and public health (articles regarding health, pathogens and their interaction with fauna and humans); b) microscopic organisms (studies focused on microorganisms); c) ecology (documents addressing the ecological interactions of two or more different taxa); d) remote sensing (studies using satellite technologies and image-based prediction or modeling programs); e) management and conservation (articles focused on the correct management of wetlands); f) birds (papers on organisms of this taxon); g) other types of fauna (studies that include taxa other than birds); h) ora and vegetation (research focused on the study of the organisms of these taxa); and i) hydrology and sediments (papers on physical-chemical parameters, sediment sampling, hydrogeology, and hydro-seismic relationships).

Data analysis
The number of articles produced annually by each country was compared; for each country, 20 values were obtained (one for each year between 2000 and 2019). The Kruskal-Wallis test was used to compare these values per country; this test was chosen because the data did not follow a normal distribution in all cases (p <0.05 for Ecuador in the Shapiro-Wilk test).
Linear regression was performed for the total number of publications (without differentiating the country) and year. The slope of the generated line was used as a reference for growth (where positive, it was considered as a tendency to increase over time). The reliability of the model was calculated using the coe cient of determination (R2).
The diversity of thematic area by country was calculated using the Shannon-Wiener index (Harper, 1999): Where pi is the proportion of studies in a given thematic area, divided by the total number of studies. A diversity T-test (Magurran 1988) was carried out to compare the diversities of thematic area across countries.
A contingency table was prepared to compare whether the proportions of the thematic areas of countries were similar. An X2 test was performed in order to evaluate the association between the proportions of the thematic areas and countries. Cramér's V coe cient was also calculated; this coe cient enables evaluation of the degree of association of qualitative variables (in this case, thematic areas) by category

Results
A total of 411 articles were reviewed; 24.8% corresponded to wetlands in Ecuador (102 articles), 37.5% (154) to wetlands in Peru, and 37.7% (155) to wetlands in Chile. The temporal distribution of scienti c production for the three countries increased over time, despite some periods of decline (Figure 1). The growth in scienti c production is con rmed, displaying a linear trend supported by an R2 = 0.77 with a positive slope (see Figure 2 for the equation's details). Chile was the only country to have produced at least one article per year during the evaluated period. For the three countries, the most signi cant period for growth in the publication of articles was 2019. Although Ecuador is the country with the fewest number of published articles, its production in 2019 was higher than that of the other countries. The average number of articles produced per year was 5.1, 7.7, and 7.8 for Ecuador, Peru, and Chile, respectively; Kruskal-Wallis analysis indicates that this production is not different between these countries (p = 0.075).
'Birds' and 'other types of fauna' were the most frequent thematic areas (with 20.7% and 19.2% of publications, respectively), followed by 'management and conservation', ' ora and vegetation' and 'hydrology and sediment' (with 15.6%, 15.1% and 13.1%, respectively). Finally, those with the lowest percentages were 'ecology', 'remote sensing', 'pathology and public health' (with 4.4% each) and 'microscopic organisms' (3.2%) (Figure 3, Table 1). According to the X2 test, each country displayed a different scienti c production in thematic areas (X 2 = 72.75 p <0.05 and V = 0.297). The largest number of studies in Ecuador is associated with 'management and conservation' and 'other types of fauna' (26.5%). In Peru, the predominant areas of study are 'birds' (25.3%) and ' ora and vegetation' (20.1%).
Chile has a higher scienti c production in studies related to 'hydrology and sediment' (24.5%) and 'birds' (20%). Finally, Peru is shown as the country with the greatest diversity in terms of thematic scope (H' = 1.969), followed by Chile (H' = 1.903) and Ecuador (H' = 1.856); despite this, no differences between the diversities of the thematic areas by country were identi ed (p> 0.05 for the diversity T-test, Table 2).

Discussion
The growing interest in coastal wetlands indicated by this study is also a trend seen in other scienti c elds, such as those related to forest ecosystems, ecosystem services and renewable energies ( . Other causes may be the increased resources devoted to research activities in recent years (Red de Indicadores de Ciencia y Tecnología 2017). The results obtained in this study indicate a linear increase in such publications, a trend that is expected to continue over the coming years; however, further studies will be required in order to con rm whether or not this increase is maintained. It is also essential that studies be developed to evaluate the use of these articles within the scienti c community, as well as by decision makers.
The presence of research centers is vital for scienti c production on any given subject (Ponomariov and Boardman 2010). In the Andean region, 51% of the organizations focused on the studying of wetlands are located in Ecuador, Peru, and Chile (Salazar-Navarro et al. 2020). However, the results of this study indicate that none of these three countries exhibits a marked difference in terms of the number of publications per year, while the three present different preferences in terms of their production. These results are also re ected in the study by Salazar-Navarro et al. (2020), where Peru is shown to have presented more studies at conferences in the eld of limnology related to 'botany', Chile to 'hydrogeology', and Ecuador to 'conservation'. Ma et al. (2013) determined that two of the leading research topics in wetlands are related to organisms and vegetation; this coincides with our results, since fauna and ora studies constitute more than 50% of published articles.
The results obtained in this study indicate the thematic areas that must be reinforced in each country. Efforts should be increased in relation to research associated with 'hydrology and sediment' in the coastal wetlands of Peru; this knowledge is crucial to understand the origin and future of wetlands in this desertic area. In Chile, studies of 'microscopic organisms' should be expanded, while in Ecuador, it is crucial that greater effort be invested in the publishing of studies on 'birds'. Among the least represented areas for the three countries is 'pathology and public health,' a relevant topic since these desertic areas are constantly affected by epidemics (e.g. Ries et al. 1992;Segovia et al. 2013; Aspilcueta-Gho 2017).
It cannot be ruled out that many publications may have been made in ways other than those considered in this study (such as books or technical documents); however, we consider it essential that scienti c production be empowered in the category of peer-reviewed articles, as well as in the databases used in the present analysis. Currently, initiatives exist which have expressed interest in protecting these ecosystems, such as the Initiative for the Conservation of Coastal Wetlands and Shorebirds on the Arid Coast of the South American Paci c (humedalescosteros.org). It is our hope that this information will serve to promote projects in areas that require special attention, such as those we have identi ed. We feel certain that the results of this study have the potential to serve to generate policies and recommendations for the continuation of research in these ecosystems which are so important to humanity.

Conclusions
A total of 411 articles concerning the coastal wetlands of Peru, Chile and Ecuador were reviewed. The most frequent subject areas were 'birds' and 'other types of fauna'; the diversity of publications was similar across the different countries, but the proportions of the total subject areas of each country varied. A growing trend is indicated in the number of papers published per year. The thematic areas that require strengthening have been identi ed, and they must be considered in order to enable decisionmakers and researchers to intensify their focus in these speci c areas within each country.  Figure 1 Articles on marine-coastal wetlands of the South American Paci c coast between 2000 and 2019, by country.

Figure 2
Articles on coastal-marine wetlands of the South American Paci c coast between 2000 and 2019; the equation resulting from the regression is included.