A systematic review of scientific research focused on farmers in agricultural adaptation to climate change (2008-2017)

Due to the severe consequences of climate change, associated risks to global food security, and the contribution of agriculture to greenhouse gas emissions, agriculture must necessarily adapt to meet these challenges. Many studies have therefore sought to investigate agricultural adaptation to climate change, and as key stakeholders in agriculture, farmers play a vital role in this process. There is a rapidly increasing corpus of scholarship on agricultural adaptation to climate change, with many studies beginning to incorporate survey methods to examine farmer perceptions and adaptation responses. Nevertheless, in-depth understanding of farmers worldwide is inadequate due to insufficiently robust methodologies, socio-economic disparities, and unequal geographic distribution. In this study, we searched and reviewed the existing peer-reviewed, English-language scientific articles published between 2008 and 2017 on agricultural adaptation to climate change that have incorporated farmers into their research methodologies. The main findings include the following: (1) a small but increasing number of studies focus on farmers in climate change adaptation; (2) the global geographic distribution of the reviewed studies is uneven, and many of the most vulnerable nations (e.g., lower-income/agricultural-dependent economies) have no representation at all; (3) there were diverse rationales and methods for incorporating farmers into the studies, and many of the methodological differences were due to practical and logistical limitations in lower-income/agricultural-dependent nations; and (4) studies were from multiple academic fields, indicating the need for more interdisciplinary collaboration moving forward because agricultural adaptation to climate change is too complex for a single discipline to fully explore. Although English is increasingly recognized as the “international language of science,” due to the challenge of language segmentation limiting broader understanding of global scholarship whenever possible, future reviews should be jointly conducted in both English and non-English languages.

Abstract 23 Due to the severe consequences of climate change, associated risks to global food security, and 24 the contribution of agriculture to greenhouse gas emissions, agriculture must necessarily adapt to 25 meet these challenges. Many studies have therefore sought to investigate agricultural adaptation to 26 climate change, and as key stakeholders in agriculture, farmers play a vital role in this process. There 27 is a rapidly increasing corpus of scholarship on agricultural adaptation to climate change, with many 28 studies beginning to incorporate survey methods to examine farmer perceptions and adaptation 29 responses. Nevertheless, in-depth understanding of farmers worldwide is inadequate due to 30 insufficiently robust methodologies, socio-economic disparities, and unequal geographic distribution. 31 In this study, we searched and reviewed the existing peer-reviewed, English-language scientific 32 articles published between 2008 and 2017 on agricultural adaptation to climate change that have 33 incorporated farmers into their research methodologies. The main findings include the following: (1) 34 a small but increasing number of studies focus on farmers in climate change adaptation; (2) the 35 global geographic distribution of the reviewed studies is uneven, and many of the most vulnerable 36 nations (e.g., lower-income/agricultural-dependent economies) have no representation at all; (3) there 37 were diverse rationales and methods for incorporating farmers into the studies, and many of the 38 methodological differences were due to practical and logistical limitations in lower- 39 income/agricultural-dependent nations; and (4) studies were from multiple academic fields, 40 indicating the need for more interdisciplinary collaboration moving forward because agricultural 41 adaptation to climate change is too complex for a single discipline to fully explore. Although English Introduction 48 Agriculture and climate change are interrelated [1,2]. On the one hand, agriculture is a 'victim' 49 of climate change, since it is sensitive to differences in climatic conditions, so climate change 50 inevitably has significant effects on agriculture [3,4]. Specifically, climate-and weather-related 51 disruptions can cause extraordinary impacts on food production and price, potentially exacerbating 52 food insecurity for millions globally [5,6]. Widely cited estimates indicate that from 1980 to 2008, 53 the global yields of two major food crops, namely, wheat and maize, dropped by 5.5% and 3.8%, 54 respectively, due to the impact of climate change [7]. On the other hand, agriculture is also a 55 substantial 'contributor' to climate change because it is a significant source of greenhouse gases 56 (GHGs) [8][9][10]. It is estimated that agriculture generates over 20% of total global anthropogenic 57 GHG emissions [3,11]. 58 Because the impacts of climate change on agriculture represent threats to quality of life on both 59 the local and global scales [4], and because agriculture has the potential to reduce GHGs by 60 advancing carbon storage technologies [12,13], wise land use management [14], and well-managed 61 cropping and grazing systems/practices [8,[15][16][17][18], calls for the development and implementation of 62 integrated climate change response strategies/policies for agriculture are increasingly urgent [19][20][21]. 63 As farmers are the key stakeholders in agriculture, the impacts of climate change on agriculture have 64 posed a direct threat to their livelihoods and well-being worldwide [22,23]. Therefore, a greater 65 understanding of farmers' beliefs [17,24] and perceptions [25,26]  were also referenced to establish the inclusion and exclusion criteria, as well as the classifications 124 and sub-categorizations of the literature (Table 1). 125

Study subject -farmers and stakeholders similar to farmers (farmer) Included
The title of the paper explicitly indicates that the 'farmer' (cultivator, grower, producer, smallholder, household, rural community, etc.) is the main or only study subject in the paper. The full text of the document includes substantive reporting or discussion of farmers' participation in climate change adaptation. In these studies, farmers were incorporated in the methodology (interviews, surveys, focus groups /workshops, etc.) to provide first-hand information that could potentially contribute 8 excluded Research papers that reported and/or discussed concepts/theories associated with climate change adaptation, as well as those with methods/models that are used to predict/assess/evaluate climate change adaptation practices, were excluded.

Human system -vulnerability, resilience and adaptive capacity excluded
Studies that assessed vulnerability to climate change in a particular agricultural system were excluded. The assessments were based on various factors (environmental, socio-economic technological, etc.). This category of studies also includes assessments of resilience and adaptive capacity. Note that none of the studies within this classification assessed the vulnerability of farmers or those similar to farmers.

Study subject -natural systems excluded
Any study that only focused on the effects of climate change on natural systems was excluded. These systems cover the biological (flora and fauna) and the physical (climate, land, soil, water, etc.) systems [67]. The impacts, risks, uncertainty, and vulnerability of natural systems are all excluded in this category.

Study subject -others excluded
Articles that were completely irrelevant to the topic were excluded. 126 The literature selection procedure involved three steps. First, we conducted a keyword search in 127 Web of Science. To yield as many relevant articles as possible, this step was conducted in the subject 128 field. To include variations of the thematic terms, Boolean operators and wildcards were applied to 129 yield the following search terms: "climat * chang * " AND "adapt * " AND "farmer." We screened for languages, those outside of the search period or those other than articles and reviews (e.g., abstracts, 134 meeting/conference proceedings, books/book sections) were excluded [65]. This step retrieved 1502 135 papers. 136 Second, we conducted a keyword search to further screen the 1502 retrieved papers for 137 relevance in this study. The main purpose was to achieve greater accuracy in identifying only those 138 studies exclusively focused on 'farmers' and adaptation to climate change. An effective way to filter 139 out non-farmer-related papers was to conduct a more precise term search in the title field of papers 140 [33,66]. To guarantee more precision in the obtained records, we defined the word 'farmer' as any 141 individual and/or a group of individuals engaged in land-based, cultivation-oriented agricultural 142 production activities that supply basic human needs (e.g., food, fibre), including farmers, cultivators, 143 growers, producers, smallholders, households, and rural communities. These selection criteria 144 narrowed the number of papers to 563. 145 In the final step, the titles and abstracts of the 563 remaining articles were individually reviewed 146 to evaluate each article's suitability for inclusion in the final review (Fig 1). We reviewed the 147 abstract of each paper, specifically looking into the context of research methodology. The aim was to 148 determine whether farmers were incorporated into the methods of each study. Cursory to in-depth 149 full-text reading was performed for those papers without abstracts to evaluate their suitability. Three 150 essential criteria had to be met simultaneously for an article to be included in the final review list: 1) 151 farmers were the only study subject or a primary study subject; 2) farmers were incorporated into the

Study objectives formulated by the scholars
Original statements in the articles were first recorded and then categorized