Thomas McGovern

Thomas McGovern, environmental archaeologist

Could you please introduce yourself?

My name is Thomas McGovern. I’m an archaeologist. I specialize in zooarchaeology, the study of animal bones. I’m based at the City University New York, both Hunter College, and also the Graduate Center.

Why does climate change matter?

Climate change is probably one of the most important things which we all have to think about in relation to our place on the planet now. We always have problems with resource depletion. We always have problems with pollution. We have problems with maintaining our own populations. But these problems are made so much more difficult in situations of uncertainty and situations of fluctuation, and this is of course where we find ourselves now. This is not the first time that we as a species have moved through dramatic climate change. The past is full of examples of human societies who have done this.

The past is also full of dramatic examples where human societies underwent painful transitions — or what people talk about as collapse — when faced with these kinds of climate changes. So the past can be both an inspiration, and a warning, as we’re all facing change on an unprecedented scale in our own lifetimes.

You mention that past societies have lived through climate change before. But isn’t the current state of affairs different from the cases we know about in the past?

The rich paleo-ecological records which has been generated for us in last decade or more by climate scientists have really underlined the extent which our species evolved during periods of profound climate change. And we’re facing one now. The last time, however, that our species faced this kind of a change in temperature was at the end of the Pleistocene, and then all of us were hunter-gatherers spread thinly across the world. Now there’s hardly any hunter gatherers left. We’re all dependent on highly structured food production systems, we’re all interconnected and there’s so many of us. So we are facing profound change on the scale of the warming at the end of the Pleistocene, [but] in a very, very different position in terms of our relationship to earth’s resources, to natural and social capital. We have both greatly much more power than any hunter-gatherer in the past had, but at the same time, our societies in some ways may be much more fragile.

Is it partly a question of scale, the difference we are experiencing now?

As we’re facing climate change on what is — on the millennial scale — unprecedented amounts, we have many different scale issues to deal with. We have the number people who we have to take care of, we have different regions that have very different vulnerabilities. We also have the problem that some of the most vulnerable people have the least power. But climate change is an equal opportunity threat. There is no possibility to have a continent unaffected, or to have a gated community which will not be impacted by climate change. This is affecting all of us. We all need to pull together and recognize [that] the threats presented to us are genuinely global, not just threats in one or two areas, although these may be the places that feel it first. It’s is happening to all of us.

As an archaeologist, what is your take on the challenges posed by climate change?

Climate change has always been one of the major forces shaping the Earth and everything on it. Our species evolved during periods of profound climate change, and we’re facing one [such change] right now. I think probably the most urgent task we have facing climate change is to organize ourselves, and to think how we can work together effectively as a species, to respond to threats which affect all of us.

Climate change has been arguably the most profound in the circumpolar North in the past decade. We’re seeing more rapid change there than we’re seeing in other parts of the world, and much of it is happening unexpectedly rapidly—things we thought from projections would be happening decades from now are happening right now.

Major changes occurring in the North, which I think have concerned myself and everyone else, are issues of rapid sea level rise and also the potential for threshold crossing climate change. We’ve seen back in the Middle Ages the impacts of sea ice formation and now we’re potentially seeing the impacts of sea ice melting throughout the circumpolar North, rapid change full of potential but also full of threat.

What are the human costs of climate change?

People who are threatened from the changes include, of course, Indigenous people, people living in the North, but I think these are changes which affect the globe. So there isn’t anyone on Earth who isn’t affected by the melting of ice sheets and there isn’t anyone who isn’t affected by the sudden accessibility of the polar North to exploration for oil, for gas, and for the transit back and forth for giant ships across the pole.

Human costs of climate change, especially in the circumpolar North, often focus on issues of coastline erosion. Whole communities are going to the sea. Heritage sites are going to the sea. Major archaeological sites are going to the sea. So sea level rise associated with increasing storminess is an immediate major threat to people living in the circumpolar North.

Could you speak to the idea to the ideas of good versus bad climate change, in light of the rush to resources in the North versus the fear over what is happening to the arctic?

In the circumpolar North there’s lots of change happening right now, but change has been a fairly constant feature of life in the North. Many people who are Indigenous folks, who have adapted to this for years, are facing this change with a sense of both challenge and opportunity. Many Greenlanders are growing vegetables in places where they never could before, and are looking forward to adapting to warmer conditions. Others are taking a very pragmatic view that change is inevitable, change is normal, change is what they’ve been experiencing for all of these thousands of years. And they are both concerned about the nature and the direction of changes but also many communities are perhaps surprisingly confident in their ability to respond. Where the concerns really are deep is where communities feel themselves tied to things they can’t control—the price of oil, distant markets. These are the sorts of things which in many respects today reduce the confidence of northern people about their ability to survive on their own. So we’re going to have to have a concerted effort to work with local communities both to mobilize their own local knowledge for global use and also to make sure they are not victims of being on a long supply chain.

Can you tell us more about the situation in the circumpolar North?

In my research area, the North Atlantic—stretching broadly from Arctic Norway through Labrador—this is an area which in the past has seen very significant climate changes taking place. The onset of drift ice, cold—talk about a little ice age—really had a major impact on people all across the area. This is one of the things which our teams have been studying for the past 30 years now—the issue of how climate change can affect the different ecosystems of the North Atlantic ranging from Greenland to Iceland, Orkney and the Faroes, ranging from places that are genuinely Arctic to northern temperate zones. These are all questions which our teams have been investigating together for quite some time. These connect up to modern issues of climate change directly because today we are seeing the same kinds of changes but perhaps in the opposite direction. Rapid warming rather than rapid cooling, but in each case the impact on local communities is going to be profound though different in different communities.

What specific effects are of particular concern in the North Atlantic?

One of the many risks caused by increasing storm threats combined with rising sea levels is the threat to a huge amount of cultural heritage that’s concentrated along the coast. The past couple of years have seen some extreme storms strike Europe, and these have revealed and destroyed sites in the same storm. So we’re having situations in places we never knew existed before. [Sites of] the Mesolithic onwards are being wiped away before we even have a chance to document them. Other heritage sites—castles, monasteries, cemeteries, places which have been known about for centuries and which are full of value to the local people, both in terms of their own well-being, but also in terms of tourist dollars—these [sites] are being destroyed frighteningly quickly.

What can be done to address these threats?

We have a need to rally resources across the world to respond to these kinds of threats which can’t be stopped like a bulldozer. The sea isn’t going to be turned back by us enacting a law. We have to work together, and with local communities very closely, to prioritize and to rescue what we can from the oncoming sea.

Rising sea level and increasing storminess pose a threat not only to known and recently discovered heritage sites but also to the scientific record that we need to better understand and to reconstruct changing climate through time. One of the things we are discovering is archeological sites are incredible archives for information about the past distribution of animals and plants, about currents, about food webs, that we never realized we could access until the development of ancient DNA studies and isotopic studies. They are broadening every week. It’s a bitter irony that just as we are really getting ourselves into position to make use of these incredibly rich stratified archives taking us back thousands of years in the past, they are being destroyed. This is the Library of Alexandria—full of knowledge, unique, unknown, and it is being burned. It is on fire as we speak. We need international help, we need coordinated effort, to rescue what we can, while we can.

As an archaeologist your work examines past societies. How does understanding of human responses in the past apply to our present-day challenges?

The past informs present to allow us to plan effectively for the future. That’s a bit of a tired thing to say, but it’s very true. Without an understanding of how humans and landscapes, currents, wind and wave, have interacted in the past, and on a millennial scale, we don’t really have any basis at all for understanding what’s about to happen to us. So knowledge of the past, the long durée, that isn’t luxury, it’s necessity if we are going to be effective in building scenarios which will take us through what [are bound to] be interesting times to genuine sustainability in the future.

When you think likely futures facing humanity, what do you picture?

I think it’s important for us to try to imagine a society for the future which is less carbon dependent. It’s the only way we’re going to get there. We all have to work together. It is not going to be easy. People will have to make sacrifices. Our understanding of what a livable lifestyle is, something which is pleasant, something which we want to have, our children to have, is going to have to be recalibrated. Sustainability cannot include the levels consumption of carbon which we are all doing today.

What do you think can be done, practically speaking, to move toward a more sustainable world?

Practical things which we can all do involve conserving, making better use of resources, going renewable. In our own lives, academics spend an awful lot of time flying around, and this uses up resources and makes an imprint. If we can make use of video conferencing, if we can make use of online resources, we can work smarter, cheaper, and with less damage to the planet.

What are the shorter-term challenges facing us?

In the short-term, I think some of our biggest challenges — at least in the area where I work, the North Atlantic — have to do with rising sea level, increasing storminess, damage to coastal landscapes, which include resources, fixed resources like harbors and ports, which include a lot of people’s homes, but also include heritage sites like cemeteries, like castles, places that have great meaning to people. From an archaeological standpoint, a great many archaeological sites extending, back thousands of years into the past — we’re now increasingly realizing — can be made use of through a range of new techniques, to give us information we can find no other way, about past environments, about past climate change, which can help to inform us about what may happen in the future.

And the long-term challenges?

Long-term changes in our area are going to be serious. [The] rise in sea level, which can impact fixed resources [that] can be really hard to move — places like Rotterdam, London, New York — are going to be very difficult to defend as time goes on.

We’re also going be facing all sorts of things we can’t anticipate, changing lifestyles, animals and plants moving around in ways which we cannot anticipate and which may appear chaotic to us. We have a lot of challenges, real challenges, and they may all pile up at once. Conjunctures of different kinds — of things happening at different rates, [on] different geographical scales — can be a real hazard when [they] all come due at once, so I think one of things we have to be concerned about is [those] things we don’t anticipate happening.

So what do we do?

I think one of the most important things for us all to do is recognize we have immediate and long-term challenges. We didn’t get into this mess in one year, or one decade, or even one century, and it’s going to take a long time for us to dig our way out. We need to build connections between people among nations, with policymakers, with stakeholders, that give us some framework for sustained response to what will be a sustained problem.

How about at the individual level?

On the individual level we can do things like recycle, we can make better use of energy, but the most important things we are going to have to do together are things we have to do together. We have to organize. We have to be politically active. We have to put pressure on policymakers to make climate change an important agenda item. We have to make it an election item for them. Otherwise it won’t be on their radar. Recycling on the individual level is great, but if it’s wiped out by decisions made on the national and International level, it’s not doing us any good. So one of the things we have to do as individuals is organize.

Changing gears here… Can you talk about what significance water has in the context of the environments you study?

If we think about water in relationship to climate change, in relationship to the area that I have been working in, the North Atlantic, it’s all over. We’ve been working in this chain of islands separated by, in some cases, hundreds of thousands of kilometers of water. Are they separated by that water or are they connected by it. This is an ongoing question of Island research. If islands were to be thought of as isolated laboratories of climate change, culture change, then they [would indeed] need to be isolated, and often it’s much more complicated than that.

As we work in the North Atlantic, one of things we’ve realized is that the interconnectedness of islands is equally as important as their isolation. So water as a highway, water is a barrier, water is the thing that brings whales and seals and sea ice, these are all the ways in which water acts in the North Atlantic, and it is pervasive.

There’s often a tendency to think in equally polarized ways about global North and South. Should we be thinking in similar relational ways about these hemispheres?

The North and global South, [like] the whole planet, are interconnected. In a recent meeting, one of the ministers of Singapore talked about how his island nation is directly connected to events and the circumpolar zone in two ways. One way he noted is that birds from the sanctuary outside of Singapore summer in the Arctic. The other reason is that all Singapore is about one and a half meters above sea level and that much more water coming up will put that city under water. So we have these connections between North and South, between different portions of the globe. Many of them come back to the North—migration, air circulation and especially rising sea level, all connects the North to the rest of the globe.

Could you explain the idea of conjuncture as explored in your work?

One of the concepts which we’ve borrowed from environment history is the idea of conjuncture—that sometimes things that are operating on different time scales and different geographical scales can combine in unexpected ways. Sometimes a trivial event can have great consequences. So one of the things we’ve been looking at is the sort of issues of when does climate change impact a particular Society? What were people doing before they were impacted? Had they essentially drawn down all the natural capital that the environment had to offer and filled it up with people? Or was there good deal of slack left in the system between where they were and what they had to do to survive?

Other issues are things like out-of-area things—trade possibilities where suddenly a product like wool or dried fish has great value where previously it was only locally useful. And in some cases, really bad things coming from the outside, like Black Death. So we have these things coming together in ways which have greater impact than if they came one thing at a time. And of course this gets us back to the whole issue of things being interconnected: social and environmental, landscape issues, these all come together and they may all have different time scales which are interacting in different ways.

Can you offer some examples of conjunctures in the North Atlantic context?

In the North Atlantic area, you can see some conjunctures coming together with the initial spread of this mixed Nordic-Celtic population out across the North Atlantic. One of the things that happened, of course, is the Viking expansion from Scandinavia, driven by many factors, many of them probably simply historical, some having to do with wealth coming in from the outside of the system. But this generates a sort of knock-on effect, where people, farming people at least, appear for the first time in Iceland and Greenland. And the conjuncture here is with a period of climate stability, which is both warmer and less stormy than in time periods both before and after. So expansion across the North Atlantic is bringing together a bunch of different factors — technological change, improvements in seafaring, improvements in navigation, intensified warfare in the North Sea area — all of which is leading people, and giving them lots of incentive, to try their hand someplace else. And this is also a time period when times were probably never better for people to make go of it, in Iceland and Greenland, that they’re coming in with a North Atlantic generalized farming economy.

Another aspect of conjuncture to think about is in Norse Greenland later on, when times are beginning to get hard. Climate change effects the Norse Greenlanders very strongly after about 1250 [AD] or so. Drift ice is coming in from South Greenland in the summertime. This is also coming at the same time where, in Europe, the interest in low-bulk, high-value prestige goods like walrus ivory, the sort of thing the Greenlanders have been supplying for generations, that continues to be of some interest but is replaced in many cases [by] decorative metal work or walrus ivory coming from other sources closer to Europe, like the Barents Sea. At the same time that you’re getting a lack of interest in the key Greenlandic trade product [i.e. walrus ivory], you are also getting a situation, because of drift ice, that is making it much more difficult for people to get from Iceland to Greenland. So the Greenlanders’ isolation, which seems to be increasing in the middle ages, is a product of both of environmental change and also of economic change happening outside of their control.

A third example of conjuncture is the Norse Greenlanders facing this reduced interest in their fundamental trade product, walrus ivory, from Europe at the same time that they’re subjected to increasing contact from Native American populations, Thule people, who are the ancestors of modern Eskimo, Inuit people of the Eastern Arctic, coming into Greenland for the first time probably sometime after year 1200. By the year 1300 we’re probably seeing permanent Inuit winter settlements down in the Norse area, intensifying contact between the two groups. It’s still not very well understood, but it’s worth noting that the very few examples we have that mention of contact between the Norse, and the people they called the Skraeling, in Greenland after 1300, are all about conflict. So if the Greenlanders, the Norse Greenlanders, are facing climate change and reduced contact with Europe by chance, by conjuncture, they are also facing this increasing cultural contact situation which may be not playing out in ways very favorable to them.

What can be said about the transmission of ecological knowledge when we think of these kinds of conjunctures, including cultural contacts, in the medieval Greenlandic context?

Any society interacts with the real world that it experiences, not directly through a fundamental understanding or absorption of nature, but through a nested series of perceptions, understandings, and not least [through] a ‘toolkit’, which many people now talk about as traditional ecological knowledge [TEK] or local and traditional knowledge [LTK]. And this can be thought of as the toolkit of culturally developed solutions to the kinds of problems that they are running into in the environments they live in.

Inuit people, for example, have highly developed TEK for moving across ice for hunting on frozen surfaces. So this is part of their tool kit for adaptation. In the North Atlantic, the Norse colonists came from a north temperate zone into progressively more arctic areas as they moved from east to west. And this gave them the opportunity, of course, to add to their toolkit of TEK, and we know that they did. In Greenland they adapted what was probably something like the Faroese pilot whale drive using boats and the whole community to driving harp seals who are not present in the eastern North Atlantic—so certainly flexibility, adaptation, and a willingness to adapt by adding to the tool kit.

But later on we also see some of the limitations of the toolkit. One of the things we see in Norse Greenland is that they don’t adopt Inuit style harpoon-based hunting. They don’t adopt the sea ice-age hunting. They are not mixing their toolkits so the TEK remains somewhat limited. Another example also to think about is TEK losing pieces of itself, losing bits of memory, losing the critical variables that let you actually go from understanding vaguely that you can do this to actually having the step by step knowledge of how to carry something out. A good example of this is the use of steatite or soapstone. This is a wonderful natural product which is stone that can be carved with a knife, and carved in almost any shape you want. Soapstone is present extensively in Norway and Shetland, and in both places it’s used back into prehistory. So this is very much part of the TEK toolkit that Norse settlers had as they moved out to the North Atlantic.

Iceland, where a whole bunch of them wound up for a few centuries, has no steatite. We know they imported steatite. We have found fragments of the material coming from somewhere further to the east, but there wasn’t anything local for people to manufacture. When the same Norse colonists moved from Iceland to Greenland around the year 1000 [AD], they again came upon extensive deposits of steatite, and again began using it. Interestingly though, the technique for carving the steatite had been changed through time. Apparently the precise details of how to work steatite, or the traditional approach to working steatite, going back to prehistory in Norway, had been forgotten. During the stay in Iceland, where steatite was not present, they apparently had lost some of the detail of how to actually do the job of working with steatite. So when people came from Iceland to Greenland they applied what looked like woodworking skills to now working in the stone. So the Greenlanders certainly made great use of steatite but their techniques for working it were subtly different from what you are seeing in contemporary Norway. So this is an example of TEK being retained at one level, the general idea that steatite is useful, but lost in another, the details of actually how to make that work.

You referenced the communal hunting practices of the Norse Greenlanders earlier? Could you elaborate on that and its importance to that society?

The Norse Greenlanders established, in Greenland, a really interesting and unique mixed hunting-herding economy. They certainly made use of all the domestic animals they brought with them from Iceland — pigs, horses, sheep, goats, cows — but they also made extensive use from the very beginning of the really large migratory seal populations, especially the harp seal, which is not present in any numbers in Iceland. So they were very flexible in changing their initial adaptation. As time went on, and especially as climate changed dramatically after the 1250s into the early 14th century, the Norse Greenlanders found themselves in a situation where the terrestrial part of their economy, the domestic animals, were increasingly having a hard time surviving. Pastures are contracting, pasture productivity is probably dropping. It is hard times to be a farmer.

We know from the animal bone collections from their deposits and also from the isotopic residues in the bones of the North Greenlanders themselves, that they dealt with this problem by increasing their marine adaptation, especially sealing. So seal bones go up to as much as 80% of the collections in Norse Greenland and as far as we can tell from dietary reconstructions, Norse Greenlanders increasingly go into the marine food web, most certainly eating seals. So we have after 1300, this incredible development of an adaptation really aimed at communal sealing, where whole groups of people would go down the fjord in boats, driving the seals into narrows, catching them in nets, catching them communally — without harpoons, the way the Inuit do it — and bringing the carcasses back for distribution.

So we have indications here that the Norse were very successful in pumping up the communal adaptation of communal sealing, going out and getting these seals in large numbers. And that got them through some very hard times. It also made them vulnerable to any climate change which caused more storminess because, of course, in this case they’re risking a key part of their whole population, and precious boats, in going out between the inner fjords and outer fjords where the seals are.

We now know from proxy evidence in the Greenland ice cores that around 1425 there’s a flip over and trend from decreasing to increasing storminess in the North Atlantic. After 1425, the frequency and severity of storms seems to have kicked up dramatically. So we’re seeing a situation here where traditional environmental knowledge, TEK, seafaring knowledge, would go from well established, drawing on centuries-long experience in Greenland, to uncharted waters literally. So Norse seafarers would suddenly be discovering that the North Atlantic they had adapted to, the understanding of what they could get away with, the luck of the draw, has suddenly changed dramatically.

Today we see something similar happening in northern communities where sea ice is changing so dramatically, that northern communities dependent on hunting and moving across the ice are facing challenges they’ve never faced before. And elders in many northern communities are now becoming reluctant to pass on their sea ice knowledge to younger hunters with the understanding that they’re just likely get somebody killed. Things have changed dramatically. So Norse Greenlanders, ironically enough, may have been incredibly successful in dealing with one environmental change, cooling temperatures, only to make themselves more vulnerable to another climate change, increasing storminess, in the later 15th century.

How can these lessons from the past regarding Norse Greenlanders help to illuminate our situation in the present?

We’re now facing, globally, climate change which we haven’t seen on this scale for many centuries. The last time the North Atlantic saw the same kinds of climate changes was during the rapid cooling of 13th and 14th centuries AD. We have examples, in the past, of how people coped or not coped with these kinds and scales of changes, so the experience of the past has a number of areas of relevance to the present and the future, not least in the case of the Norse Greenlanders, who have become sort of the poster children for unsuccessful societies who chose to fail, who did not adapt successfully to climate change.

Our understanding of the Norse Greenlanders has changed quite a lot in the past few years and it really has changed the story considerably. Now we see Norse Greenlanders as actually quite successful in adapting to the initial climate change, cooling temperatures, by increasing their emphasis on sealing and maritime adaptations, which you can see in both animal bones and in the isotopic signatures in the bodies of the Norsemen themselves in their bones.

It looks as though, increasingly, we’re seeing a situation where the very successful adaptation in the short-term to climate change—cooling—made them more vulnerable to a different kind of climate change—increasing storminess in the long-term. So [a] short-term fix can set you up for long-term problems, and this may be the bigger lesson of the Norse Greenlanders. They didn’t choose to fail, but bad things happened to them anyway.

Could you please reflect on some of the more interesting findings regarding sustainable/unsustainable societal adaptations to environmental challenges that have arisen in your own work, or in the work of your students and colleagues?

Long-term research in the North Atlantic has been really productive in having us better understand some of the millennial scale results, the decisions made 1000 years ago or more. Some of these consequences, these decisions, take quite a long time to play out. In Iceland, we have an example of a human society settling this remote mid-Atlantic island, which before humans got there, had only one land mammal—the arctic fox. They bring in a whole range of new domesticates—a full range of sheep, goats, cows, pigs and unintended domesticates like house mice are being brought in as well. So the initial footprint of humans, farmers, into the North Atlantic, and into Iceland especially, is very visible in our archeology and paleoecology.

Now the traditional explanation of what happens next is [that] the Icelanders heedlessly draw down the natural capital represented by woodland, [and] ultimately by soils, leaving the island heavily eroded with 40% or more of the soil present at [the time of] first settlement washed out to the sea or blown off into the air.

The dramatic effects of landscape change, especially of erosion, are undeniable in Iceland, but our story has changed quite a lot in terms of how this all happened. One of the things we are beginning to realize is that Icelandic farmers in the Viking age and Middle Ages were by no means foolish. They weren’t just drawing down on natural capital. In many cases we have examples of them deliberately fertilizing home fields, taking real care of sensitive environments like migratory waterfowl [and] restricting and eliminating pigs from their environment as ultimately too destructive and strongly limiting the number of goats.

So a whole bunch of the things Icelandic farmers are doing actually seem to have been quite adaptive and indeed aimed at sustainable use of the pasture resources that they depended upon, literally, for their survival. So why did things go bad? Why were there problems in some parts of Iceland? Why did erosion get its hold on chunks of the Icelandic landscape? Well, the question here is complicated, but it looks increasingly like what we’re looking at isn’t so much bad decision-making in terms of simply over-stocking too many animals in the highlands, but rather a problem of scheduling—leaving the animals, the sheep, up in the highland grazing, even a few weeks too long past the end of the growing season, seems to be the trigger, as far as we can identify, for the large scale erosion we see in late medieval and early modern periods.

Getting it wrong by a week, that’s pretty close scheduling. And what we’re seeing here then is that really the problem of Icelandic landscape managers, the people who were in charge of bringing the sheep down and getting the community ready to move the animals about, being defeated by climate fluctuation. What we’re seeing here is the evidence from increasing erosion is happening not just at times when the climate is moving in a definite direction, getting colder often, but rather in periods where one year is warm [and] another cold. A decade is pretty frosty and another one’s warm afterwards. These are times that are difficult for anyone to figure out.

Our new understanding of what seems to have actually triggered the erosion in the highlands, which then spreads to other parts of the grazing area, in ways which nobody intended — [it’s] in no one’s interest to produce an erosion desert like you see in many parts of Iceland…What we’re beginning to see increasingly is [that] it isn’t a problem of too many sheep in the highlands. It isn’t just overstocking. It’s a much more subtle issue. It’s a problem of judgement and climate.

Icelanders had to be able to keep their sheep up in the highlands as long as they could to get the maximum grazing out of the region as they possibly could. But at the same time, if you keep the sheep up in the highlands past the growing season, past the point where the highland vegetation has gone dormant, that’s when you start killing the grass, that’s when the erosion, these fissures, start opening up, that’s when things really start going to pieces in the highlands. And as far as we can tell this is a question of getting it wrong by a week. It doesn’t take much, many mistakes, to get these kinds of erosion triggers started.

The problem that Icelandic farmers faced in late Middle Ages and the early modern period was really a problem of climate change, climate fluctuation, climate predictability. We realize that they were keeping animals up in the upper pastures for as long as they possibly could, because they needed to conserve fodder elsewhere. But the question of when to bring them down was really critical and depended upon their judgment about when the growing season in the higher elevations was going to stop. And that’s, of course, when the real damage is done by grazing pressure, creating the erosion disasters which then followed. So as far as we can tell, it doesn’t take much more than a week. Getting it wrong by a week is enough to start this cascade of a disaster happening.

In much of the Middle Ages there was a clear trend in climate—it was getting colder. But for the critical periods where we think that they destabilization was taking place, the real problem was interannual variability—warm one year, cold the next, several good seasons followed by many bad ones. This is the sort of situation that’s really hard for any traditional environmental management system, or [for] any modern management system, to get right consistently. And in Iceland, with the highly erodible soils and with the general trend of climate being colder, you only have to get wrong a few times for the cascade to begin. So as far as we can now tell, the erosion story in Iceland is not one of heedless overstocking or just bad human management, it’s getting wrong by a week—almost succeeding but not quite.

What takeaways are there, for us, from these stories of past human responses to climate change?

In the medieval North Atlantic, one of the things which we are increasingly seeing, is the problem of climate fluctuation, rather than just simply of climate cooling. It isn’t that the people of the North Atlantic weren’t capable of adapting to climate change because they were, and they did several times. But what we’re seeing [in the stories of past societies] is the problem that we share with them—the problem to be able to respond to climate change which isn’t always clear cut, that isn’t always going in the same direction. Every year in the Little Ice Age wasn’t as cold as the last. Indeed, many periods were warm. It’s hard to get a trend out of that, hard to know what to do. A big thing that they lacked, that we have, is the long record of the past—both instrumental and proxy records. They give us understanding, a far better one, of the overall trend. Separating out the trend from the short-term [data] is a big problem, for them and for us. We have a few more tools than they did but we remain vulnerable to these same kinds of short-term fluctuations back and forth—cold, warm, hot, dry.

Medieval Iceland, Greenland, and the New Human Condition: A case study in integrated environmental humanities