Scoping the proximal and distal dimensions of climate change on health and wellbeing

The impacts of climate on health and wellbeing occur in time and space and through a range of indirect, complicated mechanisms. This diversity of pathways has major implications for national public health planning and influence on interventions that might help to mitigate and adapt to rapidly changing environmental conditions, nationally and internationally. This paper draws upon evidence from public health and adverse impact studies across climate science, hydrology, agriculture, public health, and the social sciences. It presents a conceptual model to support decision-making by recognizing both the proximal and distal pathways from climate-induced environmental change to national health and wellbeing. The proximal and distal pathways associated with food security, migration and mobility illustrate the diverse climate change influences in different geographic locations over different timescales. We argue that greater realization and articulation of proximal and distal pathways should radically alter how climate change is addressed as a national and international public health challenge. Electronic supplementary material The online version of this article (10.1186/s12940-017-0329-y) contains supplementary material, which is available to authorized users.


Introduction
The effects of global climate change are now observable in every part of the world.
Scientific assessments suggest that nowhere will be immune to the future threats climate change poses to human health and wellbeing [1]. Remarkably, many of the indirect adverse health impacts driven by climate-related ecological disruption and their consequences remain to be explored. Crop failures and shifting patterns in disease vectors are remote from current decision-making on energy systems and the aggregating emissions of greenhouse gases. Impacts emerge both from the physical and ecological changes across the globe, and from the societal responses such as geographic and social displacement of populations in conditions of prolonged drought or of severe and persistent flooding. Behaviours and lifestyles, as well as health, social and economic inequalities, will be profoundly affected by climate change [2,3].
We This paper does not seek to systematically review the health impacts of climate change but rather to reinforce the need for any country or community to better capture and communicate its true public health implications in a policy-relevant way.
We focus here on the adverse impacts of climate change of climate change on health and wellbeing, through what we define as proximal and distal pathways. We adopt and define the terms "proximal" and "distal" here for a specific purpose but recognize their use relates to and is informed by wider critiques when discussing causality in epidemiology and public health [4,5]. Climate change is only one yet climate change is but one amongst many huge societal challenges emerging from the complex interconnected effects of global environmental change. Addressing all Developing this theme, we argue that pathways which appear distal to national public health concerns must be made explicit within national policy and decision making. In Scotland, holistic issue framing approaches were used to facilitate a richer interpretation of the environmental contribution in health and wellbeing and especially equity [22,237,8]. This gave public health traction and influence beyond its traditional territory resulting, e.g. in public health involvement in the creation of a place standard [9].
We argue that similar approaches can provide greater traction for public health in addressing local, national and international climate change and its determinants.

Proximal and distal stressors pathways to climate-related health effects
Global environmental change, including climate change, first engaged public health interest in the late 20 th century (e.g. [4-710-13]). In the UK, for example, the public health discourse on climate change centered, initially at least, was conducted, initially at least, with a clear focus on environmental change taking place, or imminently anticipated, in that country. From the outset, concern centered, on what Comment [ CB5]: this appears to be first use of this acronym, but without definition Comment [GM6]: We have clarified this heading in the context of the subsequent changes in the section, as we reserve the terms, proximal and distal for describing pathways. The Proximal is about the "Here and Now" the Distal is about the "then and there"! the greater incidence and severity of flooding or more extreme weather in the UK would mean for the health of UK citizens [819]. In this paper we propose the term "proximal" pathway to describe the process where a population's health is imminently threatened or undermined through climate-related environmental change within its locality or within the borders of its own country and in ways readily comprehensible to that population (including its policy makers). Expressed in another way, from a national perspective, the proximal pathway is about the "here and now". on the local and immediate implications of flooding and extreme weather [8], We recognize that the health effects arising in any country from the proximal pathway closely align with the "direct" health effects described by McMichael et al. in 1996 [14] and explored further by Butler and colleagues when first introducing four classifications of adverse health effects from climate change [15]. These broad classifications were reflected in later work [16,17]. focusing on proximal, direct and often localised health threats from climate (i.e. impacts which are near in time and space). The International Panel on Climate Change (IPCC) [1,198] has predominantely highlighted disuch direct impacts. The 2015 Lancet Commission [1020] emphasises the complexity of relationships between climate-related changes and health [19], distinguishing between direct and indirect impacts.
Here, we propose the terms proximal and distal pathways to better capture/approach accurately describe the true landscape of risks for those living in a particular location or country. The near term and lived proximal experience of climate change is related to encountering local and current changes in daily and seasonal weather patterns and extreme events. These manifestations, and their implications for health and wellbeing, can be widely understood and addressed (in part) by local responses, adding a sense of urgency and purpose to local adaptation and mitigation efforts.
Again, recognizing significant conceptual overlap with the "tertiary" health impacts described by others [15,16], here we use We use the term distal pathway to to describe three indirect routes pathways by which climate change can affect both human health, and wellbeing and ecosystems. Such pathways are often mediated by both natural systems (e.g. disease vectors, water-borne diseases, air pollution) and human systems (e.g. occupational impacts, under-nutrition, and mental stress) [1].
Pathways to health and wellbeing are usually distalmay appear distal to a population in a particular location such as a country, for a combination of three reasons: they are considered temporally or spatially distal or the pathways themselves are particularly complex.
Many pathways are temporally distal because the extent of their effects on health and wellbeing will be experienced over time, or perhaps delayed for decades. The environmental changes which are component parts of these pathways lead to such impacts are difficult to discern especially in average values of, for example, regional temperature change; rainfall intensity and aggregates; reduced snow and ice coverage; increased ocean acidity; and rising sea levels. All have the potential to affect health and wellbeing, often adversely, to a degree which depends not only on the future emission occurrence trajectory, but also on the success of local and global adaptive responses. Uncertainty, compounded by a limited understanding of how these (often incremental) changes can cause damage, means that policy makers Comment [ CB15]: Again, you may want to consider inverted commas.. alas, the term is not well-known, and not necessarily self-explanatory. However, up to you.

Comment [GM17]:
Agreed, but we argue that they can be distal too because in our terms, proximal and distal are relative to the location in question. See revised text which addresses this more clearly. and the public are often much more concerned over about flooding, storms and heatwaves than about profound, widespread climatic changes. Again, using the example of the UK, climate-related sSea level rise will eventually affect health in the UK [21,22], but for the UK population, sea level rise is currently an example of a temporally distal pathway. Although many citizens in the UK can conceive some of what sea level rise might mean for their societyimmediate lives, their economy and their health, itthe full societal impacts still seems far down the line and remote [23,24].
In contrast, for the people of the Maldives, sea level rise represents an acute (temporally) proximal pathway to an imminent risk. [25]. is a very obvious example of a temporally distal pathway. Most can conceive some of what it might mean for society, the economy and health, but it still seems far down the line and remote.
Pathways from climate change to health and wellbeing can also be spatially distal.
For any country and its population, these distal pathways relate to those environmental impacts which are happening or predicted to happen elsewhere.
These can involve quite dramatic environmental changes in countries and regions beyond their borders, while little or no perceptible change in their own environment is experienced. Spatially distal pathways arise, for example, when areas elsewhere are damaged by extreme weather events leading to flooding and drought, or from more long term environment degradation and conflicts over scarce resources that result in displacement or permanent migration, or through the impact of distant events on the functioning of the global food system and therefore economic and physical access to food and local food security (see sections below on Food Security and Migration).  In the language of the IPCC Fifth Assessment Report, many of what we describe as distal pathways are "emergent from indirect, trans-boundary and long distance impacts of climate change" [1227]. The long term resource implications in responding to climate-related environmental change are rendered distal because they are also mired in complexity. For example, there is the current decision as to whether to allow fracking in the UK which will provide short term increases in fossil Comment [s26]: unfamiliar to who? To PH audiences? If you mean PH then your comment on why this is unfamiliar would be useful Comment [GM27]: I suppose public health does pride itself on its capacity to appreciate socio-ecological complexity so "unfamiliar" is not a useful inclusion here. I simply meant that the interplay is complicated and difficult for people to predict or "get their head round" . However, we have taken this out as it was not immediately clear to a reader.

Comment [s31]
: because? State reason here (rather than below) -ageing, affluence, increased power of pharmaceuticals? OR -do you mean only from CC? But, if CC leads to more poverty why will it increase?

Comment [GM32]:
We address this in the next section, which should be in sufficient proximity to the points addressed here.

Comment [ CB33]
: OK -unfamiliar with Ref 26 and I'm skeptical, but I'm not going to draw a line in the sand over this! fuel access, but which in turn will increase global CO 2 levels as well as causing significant local social, health and ecosystem impacts [1328]. Furthermore, current resource decisions will have major impacts on their equitable national and international distribution and access in the future as climate change plays out over coming decades.

A framework for distal and proximal health consequences of climate change
Unless communicated in more comprehensible and accessible ways, the distal pathways from climate change to health and wellbeing seem setwill certainly to remain fractured and illogical to a significant and influential constituency, including policy makers and politicians. Yet it is often about more than communication. For policy and other decision makers, pathways that are distal in space or time are easier to disregard. Key The consequence is that key issues will be under-accounted for in decision-making. Theis has led to a term growing demand to modernize public health around ecological principles. Sometimes termed "ecological public health",the approach accords with the new importance attributed to these distal issues "ecological public health" now describes a growing demand to modernise public health around ecological principles [3,14,1529,30].
How to achieve recognition amongst the public and policymakers that the choices they make drive current and future climate-related environmental change wherever it occurs is still a major challenge. Individual and societal choice forges the first links in every chain of events from human activities as drivers of climate change to immediate and distant health and wellbeing outcomes. However, if the necessary importance and priority are to be accorded to addressing climate change (and indeed all global environmental issues), a much broader constituency will need to have a much clearer understanding of the fundamental human reliance on natural ecosystems than currently appears to be the case. Such an understanding is central to making less opaque, particularly, the distal pathways from climate-related environmental change to health and wellbeing.  [39,40]. highlighting A common feature of many ecosystem services definitions, e.g. as used in the MEA and the UK National Ecosystem Assessment [41] is that some services provide direct benefits (provisioning, regulating and cultural ES), whereas others underpin ecosystem function (supporting ES).  It has been observed that "all models are wrong but some are useful" [43]] In addition to promoting mechanistic understanding, theThe process and the product of populating simple conceptual models, such as eDPSEEA and others, can clarify both the distal and proximal pathways through which climate change can affect health and serve as a tool for engagement with stakeholders [1934].

Proximal and distal stressors: food systems and mobility
It is evident that both short term proximal climate-related stressors, and the more

Climate change and distal food security
Food, nutrition and agricultural trade are potentially sensitive to climatic changes. While food prices provide a proximal link between food security and climate change, the distal implications of climate change are profound. The growth of demand for food is driven by rising population size and wealth, and the need for sustainabilitly. In many analyses demand is regarded as exogenous, driven by relationships with increasing wealth [4260], to which interventions need to be directed. However, the relationship between food and health are likely to shape trends in demand [3351,4260], and thus affect global agricultural production.

Climate change proximal and distal implications through migration and mobility
Climate changes involve spatial changes to economic and environmental systems that will prompt proximal and distal demographic responses. Fundamentally climate change will have an impact on where people live and on the decisions they make about moving from one location to another. Migration is a central element of economic and demographic change everywhere in the world. In effect, migration flows at the aggregate level are driven principally by differences in economic activity across space and time, though all individual decisions involve social, cultural and demographic dimensions. Some elements of the relative attractiveness of different areas, and hence the demand for migration, are sensitive to weather and climate.
Hence resource scarcity, the availability of ecosystem services, and issues of  Climate change-induced resource scarcity reduces the potential for capital accumulation in resource-sensitive economies, and thus has a potential negative impact on the mobility potential of sections of the population who do not have the resources necessary for migration migration prospects for migration. Hence, populations may experience a poverty-immobility nexus, -where increased mobility would be necessary for effective adaptation. In addition, rapid urbanization, partly amplified by migration trends of populations moving into expanding cities throughout developing and emerging economies, means that a growing number of populations Comment [s54]: Also a good par Comment [s55]: Maybe "can be temp" or "often temp" -because sometimes it is much more prolonged, as you say in the next par.

Comment [RS56]:
We have amended this sentence as suggested by the reviewer.

Comment [RS57]:
We have rephrased this section to make it more accessible -as indicated by the reviewer, our reference to differential migration patterns was not fully clear in the original version.

Comment [s58]:
Maybe for some -but from Syria, many have migrated despite poverty

Comment [RS59]:
We agree with the reviewer comment and have rephrased this section. are more exposed to weather and climate hazards in those migration destination areas.
A further interaction between migration and climate change is forced migration due to conflict. This type of migration is also typically involuntary, and has implications in both conflict areas and population-receiving areas. However,The direct links between climate risks and conflict risks are are not well established, yet the issue of attribution and causation is not the most relevant issueyet still an area of concern [4967,5068]. The IPCC Fifth Assessment Report concludes that climate change impacts are likely to exacerbate poverty in resource-sensitive regions and that since poverty is a principal driver and predicator of violent conflict, the risks of climate change amplifying conflict risks in future are real [4967]. Conflict itself has significantly differential effects on the ability of populations to relocate from conflict zones [5170]. The IPCC Fifth Assessment [1] emphasizes that Cclimate change, if it is to affect conflict risk, does so through expanding poverty as a principal cause of insecurity and conflict. Hence, in theory, there is a plausible route for increased risk in conflict-prone areas of the world over the incoming decades, in the absence of efforts for development and relief of the underlying causes of conflict in those regions [4967,68].
The principal form of migration globally, however, continues to be the movement of populations to urban centrescenters within their national borders. In terms of absolute numbers, this trend is apparent and stark in Asia and Africa in particular We have rephrased this section to reflect this comment and added further references to underpin this point.

Comment [ CB62]
: I disagree; this is not the place for debate, but it seems to depend on one's neural wiring! (ie to see the links or not) (I have corresponded extensively with Peter Geick re this.) Future policies and interventions to deal with these risks need to account for how those risks are spatially and socially differentiated, and how their accessibility is dependent on a range of social and cultural contexts, such that the benefits of those interventions are widespread [2,1020]. Similarly, the mitigation of climate change through decarbonisation of energy and altered economic systems have the potential to bring about significant benefits to health and wellbeing, especially if these are widely distributed. Despite sentinel attempts over time by various commentators [see for example [14][15][16][17], there is still a need to Concepts of public health that recognishelp people in specific locations or countries (including policymakers) eto understand and communicate climate-related health threats on vastly expanded temporal and spatial scalessL. ………………………………………………, and the complexity of both distal and proximal causes would, we argue, help to realize such benefits.
The concept of ecosystem services and recent representations of their links to human health and wellbeing [1934,246]  We agree with the point made, but it would be beyond the scope of this paper to speculate based on current evidence and knowledge.

Reviewer 1: Hilary Graham
This is an interesting and clearly-written paper addressing what many regard as the major 21 st century threat to public health. It does not present new findings and perspectives; its primary concern, instead, is to bring together existing evidence and frameworks in ways that highlight the multiple pathways through which the health effects of climate change are mediated. As I read the Abstract, this task is undertaken in order to aid public health planning and the conceptualization of interventions to mitigate and adapt to changing environmental conditions.
There are three areas where the paper could be strengthened.
Firstly, I would recommend that a clearer statement of aims and methods is given in the Abstract and then in the body of the paper. Currently, the Abstract tells the reader what the paper does ('reviews evidence' 'presents a conceptual model') but does not explain why and to what end these exercises are being undertaken. A statement of aims would help here, and should also be included in the Introduction section of the paper. Relatedly, the Abstract provides no information on methods (how the evidence was accessed and assessed etc.)and again the body of the paper has no discussion of the methods used to scope and review the evidence and scope and review potentially-relevant conceptual models. Food systems and migration feature as case studies in the later part of the paper; signally these foci in the Abstract and explaining them in the Introduction would again be helpful.
Related to this first point, it is not altogether clear where the originality of the paper lies. A crisper Abstract and Introduction would ensure that the reader is left in no doubt about this. To explain: with respect to the evidence review part of the paper, there are many existing reviews and reports summarizing evidence on health impacts of climate change and the complex pathways through which these impacts occur, including both those cited in the paper and others. So the reader may be asking 'what does the paper add?' With respect to the conceptual model, the one presented is taken from the authors' previously-published work -again the reader may therefore ask 'where is the originality?' We have reinforced both the abstract and the introduction to better address this criticism. Specifically, we have alluded to the relevance of the work to national public health planning. We recognize the overlap of proximal pathways with the direct health effects and the overlap of Distal with indirect, secondary and tertiary effects described elsewhere but we would submit this is an overlap and not a direct alignment. In our world, proximal and distal are always defined with reference to a specific population and our paper is about the benefits to public health and policy in a particular location an appreciation of the proximal and distal pathways and how they track back to a population's own health. We have proposed that this appreciation can be greatly assisted by the product and process of populating conceptual models for a particular issues. The principle of using issue framing in environmental health issues has been trialled to good effect in a Scottish environmental health policy context and can we submit be applied in an extended temporal and spatial scale. These insights are where we argue the originality of the paper lies.
Secondly, the concepts of 'proximal' and 'distal' anchor the paper. These are very familiar terms within social epidemiology and public health -and have been the subject of influential critiques. The authors should provide definitions of what they mean by the terms, particularly as they use them to refer to various points along the causal chain: proximal and distal determinants (and stressors and threats), proximal and distal pathways, proximal and distal experiences and proximal and distal effects. If they wish to discuss how they usage of the terms relates to and/or is informed by wider critiques of the terms, examples include Tony McMichael's 1999 paper 'Prisoners of the Proximate' and Nancy Krieger's 2008 paper 'Proximal, Distal, and the Politics of Causation'.
We recognize the importance of Tony McMichael's Prisoners of the Proximate and also of Nancy Kriegers papers in relation to the terms proximate and distal and have now referenced these papers. We very specifically use proximal and distal here in reference to climate change related pathways to human health for a specific country or location and we would respectfully submit they are sufficient defined in the paper.
Thirdly, there is relatively little attention given to what the evidence review and conceptual model mean in practice for public health planning and interventions (this was signaled as part of the paper's remit in the Abstract). I was expecting a section discussing how a focus on the 'proximal' and 'distal' domains helped with policy development and evaluation, particularly given the authors' important emphasis in the Introduction on equity and sustainability across societies and generations. I would suggest either this aspect of the paper is strengthened, or the Abstract and Introduction are revised to downplay it.
We appreciate the comments of the reviewer and while the relevance of the concepts we discuss for the policy domain is without any doubt an important aspect, we feel that it is too early to gauge any potential impact. The proximal and distal concept has been introduced into the discussion in the context of the UK Living With Environmental Change, with a focus on health. Our examples and other literature indicate a growing awareness and take-up of ecological public health and systematic/integrated thinking in the policy and planning process. However, adequately reflecting on how these concepts (will) support policy and planning will require both more time to analyse outcomes, but as well a wider discussion including all relevant actors within a transdisciplinary framework, which goes beyond the remit and scope of our current paper. We suggest that this point is best addressed by a follow-up publication down the line, which can address this with suitable depth and based on emerging evidence from the policy domain.
In addition to these three areas, I would encourage the authors to address two other points. First, the paper introduces an ecosystem focus (2 nd para of the Introduction). Does the term need defining and this focus explaining -and then drawn more clearly through the rest of the paper?
We refer to the ecosystem focus as it has been introduced by Rayner and Lang in their Ecological Public Health works, and link this to the conceptual understanding of how ecosystems and health are linked based on the MEA, the UK National Ecosystem Assessment and a body of peer-reviewed literature around those. We believe that a further definition beyond these foundations is not adding value to the paper, but have made several revisions/edits to the body of the text in response to this and the other reviewer's comments, which we are confident will improve the communication of our conceptual understanding of the ecosystem focus.