The impacts of climate change: from a butterfly’s microbiome to food security

This year’s UN Climate Change Conference (COP26) will be held in Glasgow in November, and now more than ever before, the pressure is on for world leaders to agree on climate action to keep global warming below 1.5°c. In the lead up to the conference, we’re asking our editors and authors to share their research at the interface of climate and ecology. In this postour Associate Editor Daniel Montoya from the Basque Centre for Climate Change (BC3) discusses two examples of climate change research from his lab:

Daniel Montoya
Journal of Animal Ecology Associate Editor

The latest IPCC report published in August 2021 not only confirms previous scientific predictions, but also presents an even more concerning scenario about the impacts of climate change worldwide. There is no time to hesitate, and even though we do not completely understand some of the consequences of climate change and its feedbacks with other global change drivers, action is badly needed both in the scientific and policy realms. This is the context that the upcoming UN Climate Change Conference (COP26) is going to face.

Understanding the impacts and consequences of climate change, as well as developing strategies to mitigate its effects, are the foundations of one of the strongest research lines in Ecology nowadays. Here, I introduce two examples – one empirical, one theoretical – of climate change research in our lab. The first example is about temperature, range shifts and butterflies. The second links climate variability and agricultural management.

Among the well-documented responses to increasing temperature are the organisms’ range shifts towards the poles and higher altitudes. Despite the plethora of studies reporting spatial expansion in populations following climate change and its consequences on species diversity and composition, and interspecific interactions, the response of host-associated microbiome communities to species range shifts is little understood. Are there general patterns in the way the microbiome responds to climate change-driven range shifts of the hosts, or are responses merely idiosyncratic – i.e. each host microbiome responds differently? More specifically, what are the effects of warming-induced range expansion on the diversity and composition of the host’s microbiome? Experimental studies suggest that higher temperatures impact the diversity and composition of host microbiomes, with implications to the organism’s physiology and survival, and to ecosystem function. Yet, observational studies of host-microbiome communities in original and expanded distributions of range-shifting species are scarce.

Credit: pixabay

This is the motivation behind the first project, which investigates how warming-induced range shifts impact gut microbial communities in species’ expanded ranges. We use two British butterfly species as case models, and compare diversity, abundance and composition of butterflies’ gut bacterial communities in original and shifted ranges. British butterflies are excellent species to study the ecological consequences of range shifts because their ecology is exceptionally well known, they are highly sensitive, and respond rapidly to, environmental change, and detailed long-term distributional data is available for them. Our results reveal a variety of effects of warming-induced range expansion on the diversity and composition of their gut microbial communities. These range from non-significant changes (bacterial richness), to idiosyncratic or butterfly-dependent changes (bacteria evenness patterns), and changes that are consistent across the two butterflies (variability in bacterial richness, core microbiome composition). The microbiome is responsible for many aspects of the host’s physiology and growth, and for ecosystem function, so if the changes in the gut microbial communities reported here apply to other species and taxonomic groups, the potential impact to biodiversity and functioning after range expansion could be severe.

With climate change not only average temperature increases globally, but also its variability – i.e. larger fluctuations in temperature values. More generally, variability in climatic extremes has increased and is going to further increase. In the second study, we explore the potential effects of climatic extremes in the provision of agricultural ecosystem services, with emphasis on biodiversity, food production and food security.

We used a model of biodiversity and crop production in intensively-managed agricultural landscapes, analyzed three main groups of stakeholders –farmers, agricultural unions, conservationists – and identified three ecosystem services that they value most – crop yield per unit of agricultural area, landscape crop production, and biodiversity, respectively. Using information given by ecosystem service trade-offs, we determined the best landscape composition (measured as the proportion of semi-natural habitat within the agricultural landscape), that corresponds to each stakeholder’s demand, and how this affects the provision of the other ecosystem services. To investigate climatic extremes, we assessed how changes in environmental stochasticity (expected under global change predictions) may affect the best landscape composition for each stakeholder and ecosystem service.

We found that higher stochasticity strongly affects the supply of ecosystem services and the best landscape composition for different stakeholders. More specifically, high stochasticity changes the relationship between ecosystem services and semi-natural habitat. For example, the unimodal relationship of landscape production as a function of the proportion of semi-natural habitat reported in previous studies becomes monotonically decreasing for high stochasticity, and this shifts maximum landscape production to lower fractions of semi-natural habitat.

When looking at real policies (e.g. EU Green Policy, Aichi Biodiversity Targets), we found that they generally target lower fractions of semi-natural habitat within agricultural landscapes than those revealed in our study. Importantly, our theoretical results and empirical studies developed in parallel have arrived to similar conclusions in terms of the fraction of semi-natural habitat to be maintained in agricultural landscapes. This study has two take-home messages. First, management for social average or multifunctionality scenario may be a better option for food security, livelihood opportunities, and biodiversity conservation, thus meeting various stakeholders’ demands. Second, agricultural policies should seriously consider global change predictions, as changes in stochasticity directly influence the best landscape compositions that maximize the provision of ecosystem services, stakeholders’ demands and food security.

These two studies illustrate that there is ample scientific evidence of the impacts of climate change on biodiversity, ecosystems and humankind. The upcoming UN Climate Change Conference (COP26) must be brave and encourage decision makers to be guided by science.

For more information on this year’s COP26 meeting, read the BES Guide to COP26.

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