Unit VIII Project
Instructions
Human Impact on Climate Change PowerPoint
After learning about several ways in which our everyday actions impact climate change, choose one action to conduct more research on and create a PowerPoint presentation to tell us more! Use the unit material and reliable online resources to gather more information.
There are several ideas with information throughout the unit but there is even more information out in the world! Think about what you do every day, and how the activity uses energy or natural resources. Think about a product you buy—how it was made, what natural resources were used to make it? You can also do a quick google search of “everyday activities that effect the environment” and start reading some articles for more ideas.
Remember to use reliable sources from the Internet. There is a lot of misinformation out there and finding reliable information can be difficult. The best sources of reference material for your presentation are scientific journals found in the CSU Online Library databases. Click here for a biology research tutorial that demonstrates how to locate library resources relating to biology You can also find reliable statistics at organization websites listed in the Unit under “Combat Climate Change.”
Your presentation must include:
What everyday activity or product have you chosen to present? Why did you choose this activity or product? Why is it important?
Connect the activity/product to its impact on the environment and climate change. How does doing the activity or making the product use natural resources, disrupt habitat, impact wildlife or other effects on the environment?
Report data and statistics, with references, on how this activity/product effects the environment.
What can people do to decrease the activity/product’s impact on the environment?
Be sure to follow the formatting and guidelines provided below:
Include at least three visual aids.
Include three reliable references, and at least one source must come from the CSU Online Library.
Use bulleted information on slides (five lines or fewer).
Include substantial and detailed speaker’s notes that include what you would say in an actual presentation. The speaker’s notes should also reflect the depth of your research.
Include a separate title slide and separate reference slide.
Use an appropriate font and background.
Include at least 11 slides, but not more than 15 slides (not counting your title slide and reference slide).
Use correct APA format for references and citations, and use correct grammar and spelling.
Upload the presentation as a .ppt or .pptx file.
Research Ideas and Outcomes 5: e34451
doi: 10.3897/rio.5.e34451
Reviewable v1
Grant Proposal
The shadow of the future and the shadow of the
past: Studying the impact of climate change on
human behaviour
Björn Vollan
‡ Philipps University Marburg, Marburg, Germany
Corresponding author: Björn Vollan ([email protected])
Received: 11 Mar 2019 | Published: 26 Mar 2019
Citation: Vollan B (2019) The shadow of the future and the shadow of the past: Studying the impact of climate
change on human behaviour. Research Ideas and Outcomes 5: e34451. https://doi.org/10.3897/rio.5.e34451
Abstract
There is consent among researchers that climate change results in increasing number of
extreme weather events, migration and even the need to resettle entire populations.
Understanding the behaviour of climate refugees and people exposed to extreme events
are key in order to avoid emergency mass movements or even conflict over natural and
social resources. I propose a research project with two related parts that identify the human
reaction to the impacts of climate change by combining a comparative research design and
the use of economic experiments, survey methods and modelling techniques. The first part
of the project builds upon a unique sample of experimentally measured risk and solidarity
preferences of 800 Filipinos taken in 2012 in. In order to assess the impact of the damages
induced by typhoon ‘Haiyan’ and the following recovery aid we will carry out two follow-up
studies with the same people in order to obtain panel data on solidarity and risk
preferences for robust statistical inference.The second part of the project will focus on the
effects of anticipated forced and permanent relocation. The major innovation offered by the
proposed set-up is a sample of inhabitants from atoll and island communities where the
communities only differ in the timing of the expected relocation due to sea level rise with
additional use of priming techniques. The set-up allows studying how preferences and
behavior of people change with the prospect of being severely affected by climate change
‡
© Vollan B. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
https://doi.org/10.3897/rio.5.e34451
http://crossmark.crossref.org/dialog/?doi=10.3897/rio.5.e34451&domain=pdf&date_stamp=2019-3-26
http://crossmark.crossref.org/dialog/?doi=10.3897/rio.5.e34451&domain=pdf&date_stamp=2019-3-26
http://crossmark.crossref.org/dialog/?doi=10.3897/rio.5.e34451&domain=pdf&date_stamp=2019-3-26
mailto:[email protected]
https://doi.org/10.3897/rio.5.e34451
and whether and how these affect short and medium-term adaptation strategies such as an
increased extraction of natural resources and migration.
Keywords
Climate Change, typhoon, sea-level rise, social preferences, lab-in-the-field experiments,
priming, network, agent-based modelling, confirmation bias, Philippines, Solomon Islands
Collaborators
Adam Douglas Henry (University of Arizona), Andreas Landmann (University of Göttingen),
Bernd Hayo (University of Marburg)
State of the art and societal challenges
Climate change, migration of human populations, and environmental degradation are
interrelated in a complex coupled human and natural system. While people have historically
abandoned places with harsh conditions, the scale of these flows is expected to increase
dramatically as a result of climate change. Environmental migrants are individuals forced to
migrate from their home region due to sudden or long-term changes to their local
environment compromising their well-being or secure livelihood. Such changes include
severe droughts, desertification, sea level rise, and disruption or intensification of seasonal
weather patterns. There is consent among researchers that climate change will result in
increasing migration and even the need to resettle entire populations. Myers (1997)
estimated that there will be 200 million environmental migrants in 2050 and later confirmed
these figures, adding that “environmental refugees will soon become the largest group of
involuntary refugees” (Myers 2002). These projections are in line with those reported by the
Intergovernmental Panel on Climate Change (IPCC) and the Stern Review on the
Economics of Climate Change.
While there exists a huge literature on the bio-physical impacts of climate change for
various regions and sectors, less is known about the impact of climate-induced migration
on natural systems. Migration can have positive and negative effects on the environment in
areas from which these migrants originate, as well as in their temporary or permanent
destinations. In order to understand these impacts it is crucial to study how climate events
change the pro-sociality of people, their social networks, and society as a whole. Such
research is not only of scientific but also of practical importance. Pro-social behaviour
spurs cooperation among resource users and stakeholders and is central to natural
resource management, community-based activities, and co-management. Understanding
how environmental context – such as differences in exposure to risk– influence cooperation
and environmental behaviour more broadly will help develop more robust theories of how
human and natural systems interact. From a practical point of view, better models will allow
2 Vollan B
us to predict how people are likely to change their behaviour in light of future climate
changes, and build scenarios about potential responses to extreme events. These
predictive models would enable us to study in a virtual environment various policy
interventions that are hypothesized to be effective instruments for reducing ecological
systems stress and protecting human well-being. In light of these considerations, I
therefore believe that my interdisciplinary and policy-oriented research project fully
supports the aims of the Robert Bosch Junior Professorship.
Fig. 1 provides a synopsis of my main research questions, and how they inform a better
understanding of the complex ways in which populations are likely to adapt to climate
changes. Ultimately, this research seeks to predict how people respond to shocks through
migration and changing patterns of resource use. My research design allows for both a
forward- and backward-looking perspective on these issues, by examining how at-risk
populations might adapt to environmental change, and by examining how populations who
have already experienced climate-related shocks responded to these shocks. This
research culminates in the development of empirically-grounded and spatially-explicit agent
based models of how populations – and the stress that populations place on natural
resources – will shift as a result of climate change.
To realize these goals, this research will address two specific research questions. First, we
need to understand how people learn about their exposure to risks. On the one hand this is
a matter of learning about risk (i.e., reducing the gap between perceived risks and actual
risks) through a combination of personal experience and information exchange with
informal social contacts or with formal organisations such as NGOs. We hypothesize that
being exposed to risks leads to an updating of beliefs about costs and benefits of certain
actions, a change in behaviour and ultimately to a change in experimentally-measured
preferences (i.e. how people value certain goods relative to other goods). Second,
understanding how people learn about risks will help us to understand people’s choices
Figure 1.
An overview of research questions.
The shadow of the future and the shadow of the past: Studying the impact … 3
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related to resource use, network formation and migration. Resource use patterns and
support from the social networks are important in itself but they also influence the likelihood
of migration. A collapsing resource base will encourage people to migrate while migration
also reduces the stress on the resource. Likewise, a strong social network may give people
the means to migrate, while on the other hand it may also strengthen emotional ties to
current locations which might prevent migration. The resulting resource use, network and
migration pattern again changes perceived and actual exposure to risk.
The research project will identify the human reaction to severe impacts of climate change
by combining an original comparative research design and the use of economic
experiments, survey methods and modelling techniques. Four PhD students will examine
the behavioural motives of potential climate refugees (shadow of the future) and people
who were exposed to extreme events (shadow of the past). Cooperation for natural
resources strongly depends on the possibility for future interactions with other community
members (i.e. having a shadow of the future) as well as on the history of past interactions
and reputation of other community members (i.e. shadow of the past). Understanding the
underlying responses of people to past and future climate events is thus, crucial to foster
cooperation and to avoid conflict over natural and social resources or even emergency
mass movements and violent conflict. Effective policy interventions will increase the quality
and quantity of alternatives available to people facing environmental degradation.
Understanding the motivations and behaviours of potential climate refugees will also allow
quantifying the expected number of migrants more accurately, which is helpful in practice
for adapting policy and legal regulations.
The methodological innovation of this study is given by the combination of:
1. controlled variation of the context people live in and the use of priming
2. economic experiments measuring people’s preferences,
3. surveys and focus groups to test the external validity of our findings, and
4. agent-based modelling for predictive scenario analyses.
Our comparative design will sample people who have been exposed to natural disasters (
shadow of the past) and people affected by different degree of sea level rise (shadow of the
future). Our research sites are the Philippines, which were affected by Typhoon Yolanda
(also known as “Haiyan”) in 2013, (shadow of the past) and the Solomon Islands (shadow
of the future). In the latter case, we sample people from low lying atolls and from islands as
well as people who already migrated from the atolls.
How does the variation in context affect behaviour? We propose that such severe changes
in perceived environmental risk also affect people’s preferences. In the same vein, the
forthcoming World Development Report 2015 draws on a large number of studies in
Behavioural Economics and asserts that context has large effects on human judgment and
behaviour; and social norms motivate much of what people do. Preference parameter
estimates are used by economists as inputs for measuring welfare and conducting policy
analysis. A huge body of literature has documented the predictive power of individual and
social preferences for individual behaviour. However, until recently, most economists have
4 Vollan B
assumed preferences (including pro-social preferences) to be exogenous. Economists take
individuals “as they are” without asking how they come to want and value things (Bowles
1998). This simplifies the analysis of planned policies or changes in the environment as
predictions about future behaviour can be more easily made*1. Indeed, according to
experimental studies, pro-social preferences develop with age from children to adolescents
but seem to remain stable over time for adults (Carlsson et al. 2014).
Yet, an emerging approach, which we also propose here, examines the relationship
between lifetime events or broader contextual factors and the evolution of preferences
using economic lab-in-the-field experiments in different settings to explore various
relationships. Experimental studies in this vein have investigated how behavior is affected,
inter alia, by market integration (Henrich et al. 2005), religion (Henrich et al. 2010),
exposure to different political systems (Ockenfels and Weimann 1999), production
technologies (Leibbrandt et al. 2013), conflict (Bauer et al. 2014, Voors et al. 2012), natural
disasters (Eckel et al. 2009 or working paper by Cameron and Shah or Cassar) and long-
term resource scarcity (Prediger et al. 2014). These studies report remarkable evidence in
favour of both long-term and short-term endogenous preference formation. Endogenous
preferences are preferences that cannot be taken as given, but are affected by external
factors. They are interdependent, in part determined by social institutions and subject to
learning and habit formation through past-experiences. Yet, if preferences change in
certain situations, then policy analysis and scenarios relying on fixed preferences might be
misleading as preferences might change simultaneously.
Objectives, concept and approach
This study contributes to a growing literature that analyses how real world context affects
human behaviour. We selected independent but interlinked topics/research sites to
examine the impact of climate change on adaptation strategies and we propose to integrate
these results in a modelling framework that allows predicting future resource use and
migration patterns.
Subproject 1: The effect of natural disaster (shadow of the past)
Subproject 2: The effect of sea level rise (shadow of the future – preferences)
Subproject 3: The effect of sea level rise (shadow of the future – information processing)
Subproject 4: Integration and Modelling
The shadow of the past
The Philippines is among the countries most vulnerable to climate change, as it is most
frequently hit by typhoons or earthquakes causing an estimated $1.6 billion in losses each
year. Catastrophic events can dramatically alter existing social and economic relationships.
Understanding and improving the way people deal with such shocks is highly important to
The shadow of the future and the shadow of the past: Studying the impact … 5
prevent future poverty. Risk-sharing could be one way to better cope with such shocks. A
large fraction of income is transferred between families to make up for losses. In a recent
experimental study in the Philippines, we confirmed these high levels of informal money
transfers among group members to compensate losses.
An emerging body of literature has examined the impact of natural disasters on
preferences and behaviour. Yet, these studies produce very different results regarding
whether people become more or less cooperative, possibly because of difficulties in
establishing causalities, in defining the interaction partner (e.g. within vs outside the
village) and using the right measurement instrument*2. One potential methodological
problem with these studies is the lack of a baseline experiment to control for initial
heterogeneities among different villages. Our study aims to fill this gap and provide solid
evidence on the formation of preferences due to past catastrophic events. To identify
causal relationships and use appropriate econometric methods of analysing panel data
sets, I plan to cooperate with Professor Bernd Hayo and his empirical research team at the
host University in Marburg.
In subproject 1, we will implement two follow-up studies in the second and fourth year
after the typhoon in order to assess the impact of the damages induced by typhoon
Yolanda. More specifically, we explore the causal effects of being hit by Yolanda building on
a unique panel data set for a range of outcome variables (especially experimentally
measured risk taking and solidarity transfers from the unaffected to the affected people, as
well as survey items on social networks and trust). Our main hypothesis is that catastrophic
events not only alter social and economic relationships but also the fundamental ways in
which people behave. Ever since Charles Darwin it has been long argued that adaptation
to the environment might favour the persistence of certain traits or behaviours that help the
survival of the group. We will link the two follow-up studies to our baseline (800 Filipinos in
2012 in Region VI) as well as to official data on reported destruction per village in order to
create a unique panel data set based on experimental games. Furthermore, we will analyse
the impact of recovery aid and how this affects social network formation and preferences.
We will also test whether existing social capital (reflected in voluntary organization
membership, collective action, trust and social relationships) prior to the catastrophic event
helped people, as individuals as well as communities, deal with the disaster.
The shadow of the future
In addition to past events, anticipated future events will also influence individual behaviour.
Many environmental scientists believe that the sea level will rise as a consequence of
global warming and the Solomon Islands will be heavily affected by such an occurrence. In
2005, it was officially decided to evacuate the 1,000 residents of the Carteret Islands, a
group of small and low-lying coral atolls belonging to Papua New Guinea neighbouring the
Solomon Islands. Given that the threats are perceived as real by scientists, the degree of
perceived risk still differs among people, since they learn in different ways about these risks
from personal experience and information exchange with informal social contacts or with
formal organisations, such as NGOs.
6 Vollan B
The major innovation offered by the proposed set-up is to sample inhabitants from atolls
and island communities in the Solomon Islands, where the communities only differ in their
expected exogenously determined impacts of sea level rise and other stochastic
environmental changes and not with regard to social, economic, cultural and historical
aspects*3. With a combination of survey and experiments and modelling we aim at
analysing how risk perception, preferences and behaviour of people change with the
prospect of being severely affected by climate change and whether and how these
preferences translate into choices for short- and medium-term adaptation strategies*4. This
could be towards more individualistic (i.e. migration and/or resource overexploitation) or
collective strategies (i.e. solidarity transfers and sustainable use of resources).
In most cases it is extremely difficult to isolate one single environmental factor as an
independent variable from which to deduce its impact on a human activity, such as
migration. This is mostly due to the fact that environmental factors are intertwined with
other social and economic factors also encouraging migration. Furthermore, it should be
taken into account that in some cases the loss of the resource base is, at least partly, self-
inflicted and not the result of a global phenomenon beyond the influence of local
populations (i.e. desertification, deforestation, soil erosion exacerbated by changing climate
conditions). In order to overcome this drawback, the proposed study will focus on one
specific population that is most likely affected by one single environmental event
exogenous to the behaviour of the population itself (in contrast to self-inflicted) and where
adaptation is expected to fail. We plan to select communities along a continuum of
expected sea level rise as well as already migrated households. According to scientific
evidence, atolls will soon and certainly inundate, while high lying islands do not face these
threats. The prospect of inundation is likely to shorten individuals’ possibilities for future
interactions which negatively affects cooperation and thus increases the likelihood of
migrating and the use of adaptation strategies that negatively affect the environment, such
as coral reef and mangrove destruction, marine pollution, land degradation, deforestation,
freshwater degradation and the depletion of fisheries. Laboratory experimental evidence
shows that the existence of a shadow of the future in an infinitely repeated social dilemma
experiment prevents people from behaving selfishly, which is the outcome of a finitely
repeated version (Dal Bo 2005). Thus, knowing that the resources cannot be used by
future generations might lead to a moral disengagement and a focus on short-term benefits
leading to the overuse of natural resources. While the hypothesis that perception of risk
encourages less sustainable behaviour (because you need to use it or lose it) seems clear,
it is less obvious whether the same expectation also holds for climate refugees in the
region to where they migrated. If the behaviour of climate refugees is only destructive in
their region of origin, then some sort of “controlled” migration could be a preferable option.
In subproject 2, we thus employ a battery of individual and social preference experiments
combined with priming videos about future sea level rise scenarios and link them to
secondary data and survey data in order to establish a causal link between perceived risks
and changes in preferences.
Since the exact remaining time horizon until inundation is unknown, it is still important to
sustainably use the available resources and actively engage in various forms of collective
The shadow of the future and the shadow of the past: Studying the impact … 7
action in order to further prevent desalination and erosion, which would aggravate the
problem leading to much earlier inundation. Bounded rationality, preference heterogeneity
among group members, and time constraints are obstacles to efficient information
generation and information revelation. In subproject 3, we will design survey experiments
related to the confirmation bias. Do people consider information that does not coincide with
their initial belief? And how does the information bias affect the willingness to migrate or
other adaptation actions.
Integration and Modelling
The research outcomes of this proposal will address a set of interlinked research questions
of high theoretical importance, but that also shed light on important policy issues for the
sustainable use of natural resources in many developing countries. Given the unique
setting of the proposed study and the range of methods used, it seems advisable to
integrate our findings within a unifying modelling framework. In subproject 4, we will
develop a series of agent-based models representing the behaviour of individuals and
study how variation in risk is likely to influence resource extraction, cooperation in social
networks, and migration. The model will allow for an examination of possible changes in
resource use over time as a result of simulated climate change, and will also model how
shocks are likely to change migration patterns and resultant patterns of resource use.
Agent-based modelling will allow for an examination of complex, emergent patterns of
behaviour resulting from a relatively simple set of individual behavioural rules that are
parameterized from experimental results. The agent-based model provides a platform for
representing basic theories of how individuals interact with each other and their
environment. In addition, the model will also provide a tool that informs decision making by
allowing users to experiment with how certain policy interventions will change the ways
individuals respond to risk, thereby changing larger-scale patterns of migration and
resource use.
Impact
The project aims at improving the knowledge in the areas of sustainable development,
natural resources exploitation, migration and climate change. As behavioural economic
research on climate change is in its infancy, there is a very good potential for scientific
breakthroughs. I expect that my results will show a strong relationship between perceived
changes in environmental risk, experimentally measured individual preferences (risk, time
and ambiguity) and social preferences. Subproject 1 and 2 will enable us to understand
how natural catastrophes and livelihood security affect people’s motivations to act and
thus, key outcome variables related to natural resource use and human development.
Stronger discounting of future benefits will lead to more uncooperative behaviour. Such
changes in risk, time and social preferences will also require changing policies, regulations
and economic modelling. One could expect that risk aversion leads to less innovation and
impatience and stronger time discounting to stronger resource use. With subproject 3 we
obtain more in-depth knowledge about information processing and learning which will be
8 Vollan B
used as input for our Agent-based model. We will also learn about the drivers of migration.
One potential result might be that incentivised controlled migration should be promoted, so
that when shocks occur their effect will not be as bad. The outcome of subproject 4 will
offer important and applicable knowledge about the interplay of migration and resource use
which can be important tools for planners and decision makers in order for quantifying the
expected number of migrants and reaction to potential policies and legislations.
Finally, the project will be an important next step in my career as environmental economist.
Funding for the proposed project will help to consolidate my research programme about
how resource users make decisions in social dilemmas and the influence of institutional
and contextual factors – particularly ecological variables. At the same time, this proposal
will allow me to continue to work on a recently emerging research about climate change
and environmental migration. More specifically, this research will produce
• several scientific research publications in leading economic and interdisciplinary
journals as well as four PhD theses and Master theses,
• improved collaboration among researchers of various disciplines,
• presentations of scientific results on various international conferences,
• third-party funding for follow-up projects.
Implementation
Study Sites
The “shadow of the past” study will be carried out in the same 30 villages that were used in
the initial study in 2012. We will try to track as many as possible of the original 810 subjects
– if necessary also using phone interviews. The experiments were conducted in the
Western Visayas (Region VI), in the province of Iloilo, Philippines. Existing databases
suggest that the region is a slightly disadvantaged but not unrepresentative of many other
regions of the Philippines. Philippine geography makes reaching and responding to the
needs of remote areas very difficult. This implies that help to cope with the frequently
occurring natural disasters (earthquake, typhoons) is mainly organised in within the
respective community. In November 2013, one of the strongest tropical cyclones ever
recorded (Yolanda), devastated portions of the Philippines, especially the Central and
Western Visayas. On Iloilo many areas were severely hit, while others were not hit at all. In
our data of 30 villages we have an even split between affected and unaffected villages.
The “shadow of the future” project will be carried out in two regions of the Solomon Islands,
which represent varying gradient sites of ongoing and future climate change impacts. First,
we will work with people of the Reef Island. The atoll inhabit small coastal communities
with an average population of 50–500 people per village. Second, we will work with
migrants from the Reef island now living in Honiara, the capital city.
Social preferences and solidarity: Intact communities are characterised by social norms
of trust and cooperation as well as social networks that control individual resource
The shadow of the future and the shadow of the past: Studying the impact … 9
extraction strategies. In the shadow of the past study, we will focus on solidarity
experiments, which we already applied in the Philippines before. Solidarity generates and
sustains strong feelings of togetherness and social-cohesion, resulting in collective action
and mutual aid (e.g. informal risk-sharing arrangements). An adequate experimental tool to
capture the relation between inherent risks of everyday life and mutual aid is the “solidarity
game” introduced by Selten and Ockenfels …
International Journal of
Environmental Research
and Public Health
Review
Climate Change and Human Health: A Review of
Allergies, Autoimmunity and the Microbiome
Carly Ray and Xue Ming *
Department of Neurology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA; [email protected]
* Correspondence: [email protected]; Tel.: +1-973-972-2922
Received: 29 April 2020; Accepted: 29 June 2020; Published: 4 July 2020
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Abstract: The impact of climate change on human health is a topic of critical importance. While only
recently beginning to gain attention, it is clear that immediate action is necessary to minimize this
impact. In our review, we will outline a subset of these effects in detail. We will examine how climate
change has worsened respiratory allergic disease. We will discuss how climate change has altered
antigen exposure, possibly disrupting antigen-specific tolerance by the immune system, leading,
in turn, to an increase in the prevalence of immunologic diseases. Finally, we will explore how the loss
of biodiversity related to climate change may affect the microbiome, potentially leading to dysbiosis,
inflammatory, autoimmune and neurologic diseases.
Keywords: climate change; allergy; autoimmunity; microbiome; dysbiosis; neurodevelopment
1. Introduction
A warming climate has the potential to profoundly impact human health. The effects are
widespread. As stated by the World Health Organization (WHO) Director-General in 2008, “climate
change will affect, in profoundly adverse ways, some of the most fundamental determinants of health:
food, air, water. In the face of this challenge, we need champions throughout the world who will work
to put protecting human health at the centre of the climate change agenda” [1]. In this review, we
will discuss in detail the relationship between climate change and allergies. While this topic has been
previously discussed in the literature, we propose that there may be a more profound link between the
two, i.e., that our changing climate may not only be worsening the condition of those with existing
allergies, but also triggering allergies in those who are disease-naive. In addition, we will explore a
possible link between current human practices and a declining biodiversity with disturbance to the
human microbiome and increasing autoimmunity.
2. Allergy and Climate Change: What We Already Know
It is well documented that climate change leads to worsening symptoms in patients with
established allergic disease. Patients with chronic respiratory allergic disease such as asthma and
allergic rhinoconjunctivitis are at particular risk due to increased exposure to pollen, as well as the
increased concentration and distribution of air pollutants [2].
As reported by the American Academy of Allergy Asthma & Immunology (AAAAI), climate
change has both increased the intensity of the pollen season as well as prolonged its duration [3]. A
retrospective study on allergenic pollen abundance and seasonality was published in the 2019 issue of
The Lancet Planetary Health. Researchers analyzed global datasets containing data on pollen season
duration and intensity for 17 locations across multiple continents in the northern hemisphere. The
study found an increase in annual pollen load for 12 of the locations, as well as a significant increase
in pollen season duration for 11 out of the 17 locations. Annual increases in maximum temperatures
Int. J. Environ. Res. Public Health 2020, 17, 4814; doi:10.3390/ijerph17134814 www.mdpi.com/journal/ijerph
http://www.mdpi.com/journal/ijerph
http://www.mdpi.com
https://orcid.org/0000-0003-0752-5777
http://www.mdpi.com/1660-4601/17/13/4814?type=check_update&version=1
http://dx.doi.org/10.3390/ijerph17134814
http://www.mdpi.com/journal/ijerph
Int. J. Environ. Res. Public Health 2020, 17, 4814 2 of 7
were significantly associated with an increase in pollen load, demonstrating a link between the two
phenomena [4].
The heightened intensity of the pollen season can be attributed to the increased concentration
of pollen. Climate change is, in part, a result of the increase in atmospheric greenhouse gases such
as carbon dioxide, nitrous oxide and methane. In a review by Lewis et al. on atmospheric carbon
dioxide and plant biology, increases in carbon dioxide were shown to lead to a reflexive increase in
plant reproduction and total pollen levels. Carbon dioxide is one of four major resources required
by plants for successful photosynthesis. As CO2 concentrations have risen, so too has the growth of
plant species that thrive at high CO2 concentrations (“C3” plants) as well as their pollen byproducts [5].
Ragweed pollen for example, one of the major causes of respiratory allergy, has been increasing in
concentration, with models predicting that levels will increase by 4 times compared to the current
values within the next 30 years [6]. Thunderstorms, which have become more frequent due to rising
sea temperatures, have been found to increase concentrations of pollen grains at ground level. After
absorbing water, these grains can rupture from osmotic shock, releasing allergenic particles that can
induce severe asthmatic symptoms in patients with asthma, hay fever and allergic rhinitis [7].
As described by Katelaris et al., clinical evidence showed that the aforementioned changes in
pollen led to increased respiratory allergic disease, evident from correlations between pollen and
respiratory disease exacerbations [2]. A recent study performed in Melbourne, Australia found a
dose-response association between ambient grass pollen levels and the same day risk of childhood
asthma presentations to the emergency department [8].
Climate change has also been linked to increased concentrations and distribution of air pollutants
such as ozone, nitric oxide and other volatile organic chemicals. There is a growing body of evidence
suggesting that these airborne environmental pollutants may be partially responsible for the substantial
increase in allergic respiratory disease seen in industrialized countries over the past several decades [9].
The results of several studies suggest that the inhalation of air pollutants may potentiate the airway
response to inhaled allergens in persons predisposed to atopic disease. The inhalation of air pollutants,
notably diesel exhaust particles (DEPs), sulfur dioxide and nitrogen dioxide, has been found to cause
inflammation and increased mucosal permeability within the airways, ultimately allowing increased
barrier penetrance by allergens. Oxidative stress is thought to be the major mechanism through which
this occurs. Oxidants produced by pollutants within respiratory mucosal epithelial cells trigger the
release of inflammatory mediators, causing the destruction and apoptosis of respiratory mucosal cells,
and eventually leading to bronchial hyperreactivity. In addition to increasing mucosal permeability,
DEPs in particular can bind to pollens, animal and other allergens, directly facilitating their entry into
the respiratory epithelium [10].
Early exposure to air pollutants has also been linked to an increased risk of incident asthma, allergic
rhinitis and eczema in children. A follow-up to the Toronto Child Health Evaluation Questionnaire
(T-CHQ) study found that exposure to ozone and nitrogen dioxide at birth was associated with a 17%
increased risk for developing asthma at around 4 years of age, and a 7% increased risk for developing
eczema at 3.5 years [11]. A systematic review and meta-analyses of birth cohort studies examining
the impacts of childhood exposure to traffic-related air pollution (TRAP) found that early exposure
to particulate matter was associated with increased risk of asthma, sensitization to aero and food
allergens, and the development of eczema and hay fever [12].
What we know: We know that climate change has worsened allergies in those with established
respiratory allergic disease.
3. Immunologic Disease and Climate Change: Is There a Deeper Link?
As described above, there is ample evidence supporting the link between climate change and
worsening respiratory allergic disease. We hypothesize that the relationship between climate change
and immunologic diseases such as allergies may be more extensive, i.e., that a warming climate may
Int. J. Environ. Res. Public Health 2020, 17, 4814 3 of 7
result in an erratic immune system and consequently, the emergence of allergic and autoimmune
disease in the disease-naïve population.
The immune system has the ability to differentiate pathogenic antigens from benign antigens
found in our everyday environment. When an antigen is identified as innocuous, the body has the
ability to suppress the immune system from initiating an inflammatory response. Our understanding
of this mechanism of tolerance remains incomplete; however, various models have been proposed. As
explained by Vickery et al., the gastrointestinal tract is continuously exposed to an extremely diverse
profile of antigens. These include benign environmental antigens such as food proteins, harmful
exogenous pathogens and commensal microbiota. The gut has a system for the antigen-specific
suppression of immune response that involves T-cells, antigen presenting cells, cytokines, B-cells and
antibodies [13]. The development and maintenance of this immune tolerance is critical, as loss or
failure of tolerance can result in disorders such as autoimmunity, allergy, respiratory illnesses such as
rhinitis or asthma, and even irritable bowel syndrome. As described in our prior article [14], climate
change has dramatically altered the profile of antigens our bodies are exposed to. While many of these
antigens are benign, it is possible that the extent of this change has overwhelmed the immune system’s
long-standing ability for antigen-specific tolerance, and the increasing molecular mimicry due in part
to increasing exposure to allergens, is leading to a rise in immunologic disease.
Analysis of CDC surveillance and reporting data shows that immunologic disorders are on the
rise [15,16]. Food allergies are one example. Recent data from Northwestern University showed
that 10.8% of adults in the US have a food allergy, with 48% of those developing at least one such
allergy as an adult [17]. According to research from the American College of Allergy, Asthma and
Immunology, peanut allergy in children increased by 21 percent from 2010 to 2017 [18]. In a 2016 New
Jersey Monthly article, Joanna Buffum outlined the ways in which the increase in food allergies among
children has changed the public school experience. There are now rules regulating food, including
making classrooms peanut-free. In 2013, the CDC published the first comprehensive guidelines for the
management of food allergies in schools. As stated by one mother, “kids didn’t have these problems
when I was young”. Studies investigating the cause for this surge are underway [19]. The notion
that climate change may be one of the inciting factors is supported by several studies which have
found that increases in CO2 and temperature are correlated with changes in the composition of peanut
(Arachis hypogaea), potentially altering its antigenicity [20].
The deeper link: Climate change has altered our antigen exposure, potentially disrupting
antigen-specific tolerance by the immune system and increasing the incidence of molecular mimicry
within the body. This may explain in part the surge in immunologic disease that has been observed in
recent years.
4. A Shifting Environment and the Microbiome: Dysbiosis and Inflammatory Diseases
The human gastrointestinal tract consists of an estimated 100 trillion microbes from at least 160
different species. Studies have shown that the composition of the microbiota fluctuates early in life,
influenced by external factors such as one’s environment and diet. As an individual reaches adulthood,
their microbiome profile typically stabilizes. It has become clear that these commensal bacteria play an
active role in human immunity, from the maintenance of barrier defense to the development of immune
tolerance. There is a growing body of literature demonstrating that disruption of the microbiome,
known as dysbiosis, can lead to a variety of secondary effects within the body. Gut microbiome
dysbiosis can lead to the development of infectious, inflammatory and autoimmune disease. Loss of
biodiversity as a result of climate change will be explored as a possible vector of this dysbiosis.
4.1. The Effects of Dysbiosis
The microbiota plays an important role in the maturation of the immune system. Through
processes such as toll-like receptor recognition of microbe-associated molecular patterns (MAMPs),
the body learns to differentiate between commensal microbes and pathogenic bacteria. In addition,
Int. J. Environ. Res. Public Health 2020, 17, 4814 4 of 7
gut microbes are involved in T-cell differentiation, T-regulatory and T-helper 2 responses, and the
maintenance of gut epithelial integrity [21,22]. Perturbations of intestinal microbiota, i.e., dysbiosis,
can lead to the dysfunction of these processes and increase the risk for multiple inflammatory and
autoimmune disorders. This dysbiosis-induced immune dysregulation is supported by studies showing
that patients with these diseases have microbiota profiles that differ from healthy controls. For example,
one study found a four-fold increase in the concentration of Ruminococcus gnavus in the intestinal
epithelia of patients with both Crohn’s disease and Ulcerative Colitis, compared to healthy controls.
R. gnavus has been linked to other inflammatory diseases including spondyloarthritis and infantile
eczema [23,24].
The relationship between dysbiosis and allergy has been well established. Observational studies
have demonstrated that disruption of gut colonization early in life, for example due to cesarean
section or lack of breastfeeding, can lead to altered microbiota profiles and increased incidence of
allergic disease [25]. Reports have also implicated dysbiosis in the development of food allergy, with
several studies finding differences in the microbial makeup of children with food allergies compared
to healthy controls [26]. A cross-sectional study found increased levels of Clostridium sensu stricto
and Anaerobacter, and decreased levels of Bacteroides and Clostridium XVIII in children with food
allergies [27]. A recent prospective study found that low gut microbial richness at 3 months of age
preceded food sensitization at 12 months [28].
The effect of dysbiosis on the human body is not limited to the development of autoimmune and
inflammatory diseases. Murine models have implicated the microbiota in CNS development, and
dysbiosis has been linked to neurologic diseases such as multiple sclerosis, autism and Parkinson’s
disease (PD). Patients with PD have been found to have abnormal microbiota profiles, and current
research suggests that gastrointestinal dysfunction may be a trigger for alpha-synuclein aggregation in
neurons [29]. Microbiome imbalance and increased gut permeability have been implicated in autism
spectrum disorder (ASD). In my own research, I found abnormal amino acid metabolism, increased
oxidative stress, and altered gut microbiomes among a subset of patents with ASD [30]. It has been
suggested that the so-called gut–brain axis may play a role in several neurodevelopmental disorders.
4.2. Microbiome and Biodiversity Loss
A 2019 global report released by the Intergovernmental Science-Policy Platform on Biodiversity
and Ecosystem Services (IPBES) announced that biodiversity “is declining faster than at any time in
human history”, claiming that nearly 1 million animal and plant species are threatened with extinction.
Climate change was cited as a leading factor for this decline, with changes in land and sea use and
pollution also being implicated [31]. With this decline in macrodiversity comes an accompanying
decline in microdiversity [32].
The “biodiversity hypothesis” suggests that reduced contact between people and a biologically
diverse natural environment may adversely affect the microbiota and its immunomodulatory
capacity [32]. Many members of the scientific community support this hypothesis, such as The
World Allergy Organization (WAO), who declared that “biodiversity loss leads to reduced interaction
between environmental and human microbiotas, which in turn may lead to immune dysfunction and
impaired tolerance mechanisms.” In their statement, the WAOJ suggested that these changes may
account in part for the increase in the prevalence of asthma, allergy and inflammatory disease in the
developed world [33]. Von Hertzen et al. outlined a mechanism for this hypothesis, suggesting that
microbial deprivation can lead to impaired immunoregulatory circuits. In the absence of adequate
microbial stimuli through the skin, gut and respiratory tract, IL-10, TGFβ, regulatory dendritic cell and
regulatory T-cells (TREG) are not sufficiently induced, leading to an inflammatory environment. In
such an environment, TREG cells are converted to T-helper 17 cells (TH17), ultimately enriching bacteria
that tolerate inflammatory mediators [34].
Studies dating back to 2005 support this hypothesis, showing that exposure to rich microbial
environments correlates with protection against the development of future allergic and autoimmune
Int. J. Environ. Res. Public Health 2020, 17, 4814 5 of 7
disease [35,36]. When compared to a reference group, school aged children living on farms were found
to be exposed to a wider range of microbes and have lower prevalences of asthma and atopy [37].
There is also evidence that, compared to healthy controls, patients with atopy tend to reside in areas
of lower environmental biodiversity (i.e., plant species, land types). In one study, individuals with
atopic disease were found to have reduced diversity of cutaneous gammaprotectobacteria, a bacteria
found in the soil and above-ground vegetation. There was a significant correlation between amounts
of gammaproteobacteria and IL-10 expression in healthy participants, suggesting that the bacteria may
have a protective effect against allergy [32].
Climate, current practices and the gut: The microbiome is a key player in the development and
maintenance of the immune system. It has also been implicated in central nervous system development.
Dysfunction as a result of a lack of immersion in biodiverse natural surroundings can lead to serious
inflammatory, autoimmune and neurologic diseases.
5. Future Steps
In the above review, we have demonstrated various ways in which climate change has the
potential to affect the human body. To minimize this impact, we must end the destruction of our
natural environment, decrease emissions of greenhouse gases and urge our peers to adopt more “green”
behavior. We have also explored the impact of broader shifts in human practices such as decreased
exposure to nature and the use of antimicrobials on subsequent health and disease development. With
research demonstrating links between the microbiome and autoimmune, inflammatory, and neurologic
diseases, it is critical that we minimize antimicrobial exposure. This may involve altering guidelines
for the prescription of antibiotics by medical professionals. In addition, given that the microbiome is
directly impacted by our daily environment, it is important to regularly immerse ourselves in nature
and familiarize ourselves with biodiverse surroundings.
6. Conclusions
It is clear that the effects of climate change extend beyond the natural environment and into the
human body. In this review, we have detailed several of these effects. A warming climate has caused
exacerbation of existing respiratory allergic diseases and is implicated in the surge of allergies and
autoimmunity in those who were previously disease naive. Climate change has dramatically altered
the profile of antigens our bodies are exposed to, bombarding our immune systems and potentially
overwhelming its ability for antigen-specific tolerance. More broadly, shifts in current human practices
such as the use of antimicrobials and decreased immersion in biodiverse surroundings have effects
on the microbiome. Dysbiosis has serious implications, as has been linked to the development of
inflammatory, autoimmune and neurologic disease. Climate change is no longer an issue for future
generations. It is affecting every one of us, now. If we do not act immediately, its impact on human
health will undoubtedly worsen. Our bodies have the incredible ability to adapt to environmental
change; however, adaptation takes generations. It is imperative that we work to halt climate change,
not only to save our planet, but also to save our own lives.
Author Contributions: Conceptualization, X.M. methodology, C.R.; Resources, X.M.; Data curation: C.R., X.M.;
writing—original draft preparation, C.R.; writing—review and editing, X.M. and C.R.; Supervision, X.M. All
authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Conflicts of Interest: The authors declare no conflict of interest.
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