̽��ֱ�� of Cambridge - Department of Geography

Extreme drought contributed to barbarian invasion of late Roman Britain, tree-ring study reveals

ta385 — Thu, 17 Apr 2025 06:00:00 +0000

̽��ֱ��‘Barbarian Conspiracy’ of 367 CE was one of the most severe threats to Rome’s hold on Britain since the Boudiccan revolt three centuries earlier. Contemporary sources indicate that components of the garrison on Hadrian’s wall rebelled and allowed the Picts to attack the Roman province by land and sea. Simultaneously, the Scotti from modern-day Ireland invaded broadly in the west, and Saxons from the continent landed in the south.

Senior Roman commanders were captured or killed, and some soldiers reportedly deserted and joined the invaders. Throughout the spring and summer, small groups roamed and plundered the countryside. Britain’s descent into anarchy was disastrous for Rome and it took two years for generals dispatched by Valentian I, Emperor of the Western Roman Empire, to restore order. ̽��ֱ��final remnants of official Roman administration left Britain some 40 years later around 410 CE.

̽��ֱ�� ̽��ֱ�� of Cambridge-led study, published today in Climatic Change, used oak tree-ring records to reconstruct temperature and precipitation levels in southern Britain during and after the ‘Barbarian Conspiracy’ in 367 CE. Combining this data with surviving Roman accounts, the researchers argue that severe summer droughts in 364, 365 and 366 CE were a driving force in these pivotal events.

First author Charles Norman, from Cambridge’s Department of Geography, said: “We don’t have much archaeological evidence for the ‘Barbarian Conspiracy’. Written accounts from the period give some background, but our findings provide an explanation for the catalyst of this major event.”

̽��ֱ��researchers found that southern Britain experienced an exceptional sequence of remarkably dry summers from 364 to 366 CE. In the period 350 to 500 CE, average monthly reconstructed rainfall in the main growing season (April–July) was 51 mm. But in 364 CE, it fell to just 29mm. 365 CE was even worse with 28mm, and 37mm the following year kept the area in crisis.

Professor Ulf Büntgen, from Cambridge’s Department of Geography, said: “Three consecutive droughts would have had a devastating impact on the productivity of Roman Britain’s most important agricultural region. As Roman writers tell us, this resulted in food shortages with all of the destabilising societal effects this brings.”

Between 1836 and 2024 CE, southern Britain only experienced droughts of a similar magnitude seven times – mostly in recent decades, and none of these were consecutive, emphasising how exceptional these droughts were in Roman times. ̽��ֱ��researchers identified no other major droughts in southern Britain in the period 350–500 CE and found that other parts of northwestern Europe escaped these conditions.

Roman Britain’s main produce were crops like spelt wheat and six-row barley. Because the province had a wet climate, sowing these crops in spring was more viable than in winter, but this made them vulnerable to late spring and early summer moisture deficits, and early summer droughts could lead to total crop failure.

̽��ֱ��researchers point to surviving accounts written by Roman chroniclers to corroborate these drought-driven grain deficits. By 367 CE, Ammianus Marcellinus described the population of Britain as in the ‘utmost conditions of famine’.

“Drought from 364 to 366 CE would have impacted spring-sown crop growth substantially, triggering poor harvests,” Charles Norman said. “This would have reduced the grain supply to Hadrian’s Wall, providing a plausible motive for the rebellion there which allowed the Picts into northern Britain.”

̽��ֱ��study suggests that given the crucial role of grain in the contract between soldiers and the army, grain deficits may have contributed to other desertions in this period, and therefore a general weakening of the Roman army in Britain. In addition, the geographic isolation of Roman Britain likely combined with the severity of the prolonged drought to reduce the ability of Rome to alleviate the deficits.

Ultimately the researchers argue that military and societal breakdown in Roman Britain provided an ideal opportunity for peripheral tribes, including the Picts, Scotti and Saxons, to invade the province en masse with the intention of raiding rather than conquest. Their finding that the most severe conditions were restricted to southern Britain undermines the idea that famines in other provinces might have forced these tribes to invade.

Andreas Rzepecki, from the Generaldirektion Kulturelles Erbe Rheinland-Pfalz, said: “Our findings align with the accounts of Roman chroniclers and the seemingly coordinated nature of the ‘Conspiracy’ suggests an organised movement of strong onto weak, rather than a more chaotic assault had the invaders been in a state of desperation.”

“ ̽��ֱ��prolonged and extreme drought seems to have occurred during a particularly poor period for Roman Britain, in which food and military resources were being stripped for the Rhine frontier, while immigratory pressures increased.”

“These factors limited resilience, and meant a drought induced, partial-military rebellion and subsequent external invasion were able to overwhelm the weakened defences.”

̽��ֱ��researchers expanded their climate-conflict analysis to the entire Roman Empire for the period 350–476 CE. They reconstructed the climate conditions immediately before and after 106 battles and found that a statistically significant number of battles were fought following dry years.

Tatiana Bebchuk, from Cambridge’s Department of Geography, said: “ ̽��ֱ��relationship between climate and conflict is becoming increasingly clear in our own time so these findings aren’t just important for historians. Extreme climate conditions lead to hunger, which can lead to societal challenges, which eventually lead to outright conflict.”

Charles Norman, Ulf Büntgen, Paul Krusic and Tatiana Bebchuk are based at the Department of Geography, ̽��ֱ�� of Cambridge; Lothar Schwinden and Andreas Rzepecki are from the Generaldirektion Kulturelles Erbe Rheinland-Pfalz in Trier. Ulf Büntgen is also affiliated with the Global Change Research Institute, Czech Academy of Sciences and the Department of Geography, Masaryk ̽��ֱ�� in Brno.

Reference

C Norman, L Schwinden, P Krusic, A Rzepecki, T Bebchuk, U Büntgen, ‘Droughts and conflicts during the late Roman period’, Climatic Change (2025). DOI: 10.1007/s10584-025-03925-4

Funding

Charles Norman was supported by Wolfson College, ̽��ֱ�� of Cambridge (John Hughes PhD Studentship). Ulf Büntgen received funding from the Czech Science Foundation (# 23-08049S; Hydro8), the ERC Advanced Grant (# 882727; Monostar), and the ERC Synergy Grant (# 101118880; Synergy-Plague).

Three consecutive years of drought contributed to the ‘Barbarian Conspiracy’, a pivotal moment in the history of Roman Britain, a new Cambridge-led study reveals. Researchers argue that Picts, Scotti and Saxons took advantage of famine and societal breakdown caused by an extreme period of drought to inflict crushing blows on weakened Roman defences in 367 CE. While Rome eventually restored order, some historians argue that the province never fully recovered.

Our findings provide an explanation for the catalyst of this major event.

Charles Norman

Adam Cuerden

Milecastle 39 on Hadrian's Wall

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Licence type:

Public Domain

Turbocharging the race to protect nature and climate with AI

lw355 — Sun, 06 Apr 2025 17:00:51 +0000

Rebalancing the planet must happen faster. Cambridge researchers are using AI to help.

̽��ֱ��Cambridge Awards 2024 for Research Impact and Engagement

zs332 — Mon, 03 Feb 2025 10:27:01 +0000

Meet the winner of the Cambridge Awards 2024 for Research Impact and Engagement and learn more about their projects.

Wildlife monitoring technologies used to intimidate and spy on women, study finds

jg533 — Mon, 25 Nov 2024 00:01:44 +0000

Remotely operated camera traps, sound recorders and drones are increasingly being used in conservation science to monitor wildlife and natural habitats, and to keep watch on protected natural areas.

But Cambridge researchers studying a forest in northern India have found that the technologies are being deliberately misused by local government and male villagers to keep watch on women without their consent.

Cambridge researcher Dr Trishant Simlai spent 14 months interviewing 270 locals living around the Corbett Tiger Reserve, a national park in northern India, including many women from nearby villages.

His report, published today in the journal Environment and Planning F, reveals how forest rangers in the national park deliberately fly drones over local women to frighten them out of the forest, and stop them collecting natural resources despite it being their legal right to do so.

̽��ֱ��women, who previously found sanctuary in the forest away from their male-dominated villages, told Simlai they feel watched and inhibited by camera traps, so talk and sing much more quietly. This increases the chance of surprise encounters with potentially dangerous wildlife like elephants and tigers. One woman he interviewed has since been killed in a tiger attack.

̽��ֱ��study reveals a worst-case scenario of deliberate human monitoring and intimidation. But the researchers say people are being unintentionally recorded by wildlife monitoring devices without their knowledge in many other places - even national parks in the UK.

“Nobody could have realised that camera traps put in the Indian forest to monitor mammals actually have a profoundly negative impact on the mental health of local women who use these spaces,” said Dr Trishant Simlai, a researcher on the 'Smart Forests' project in the ̽��ֱ�� of Cambridge’s Department of Sociology and lead author of the report.

“These findings have caused quite a stir amongst the conservation community. It’s very common for projects to use these technologies to monitor wildlife, but this highlights that we really need to be sure they’re not causing unintended harm,” said Professor Chris Sandbrook, Director of the ̽��ֱ�� of Cambridge’s Masters in Conservation Leadership programme, who was also involved in the report.

He added: “Surveillance technologies that are supposed to be tracking animals can easily be used to watch people instead – invading their privacy and altering the way they behave.”

Many areas of conservation importance overlap with areas of human use. ̽��ֱ��researchers call for conservationists to think carefully about the social implications of using remote monitoring technologies – and whether less invasive methods like surveys could provide the information they need instead.

Intimidation and deliberate humiliation

̽��ֱ��women living near India’s Corbett Tiger Reserve use the forest daily in ways that are central to their lives: from gathering firewood and herbs to sharing life’s difficulties through traditional songs.

Domestic violence and alcoholism are widespread problems in this rural region and many women spend long hours in forest spaces to escape difficult home situations.

̽��ֱ��women told Simlai that new technologies, deployed under the guise of wildlife monitoring projects, are being used to intimidate and exert power over them - by monitoring them too.

“A photograph of a woman going to the toilet in the forest – captured on a camera trap supposedly for wildlife monitoring - was circulated on local Facebook and WhatsApp groups as a means of deliberate harassment,” said Simlai.

He added: “I discovered that local women form strong bonds while working together in the forest, and they sing while collecting firewood to deter attacks by elephants and tigers. When they see camera traps they feel inhibited because they don’t know who’s watching or listening to them – and as a result they behave differently - often being much quieter, which puts them in danger.”

In places like northern India, the identity of local women is closely linked to their daily activities and social roles within the forest. ̽��ֱ��researchers say that understanding the various ways local women use forests is vital for effective forest management strategies.

Reference: Simlai, T. et al: ‘ ̽��ֱ��Gendered Forest: Digital Surveillance Technologies for Conservation and Gender-Environment relationships.’ November 2024. DOI:10.17863/CAM.111664

Camera traps and drones deployed by government authorities to monitor a forest in India are infringing on the privacy and rights of local women.

Nobody could have realised that camera traps put in the Indian forest to monitor mammals actually have a profoundly negative impact on the mental health of local women who use these spaces.

Trishant Simlai

Researcher interviewing a local woman in India

Yes

Study uncovers earliest evidence of humans using fire to shape the landscape of Tasmania

sc604 — Fri, 15 Nov 2024 19:00:00 +0000

A team of researchers from the UK and Australia analysed charcoal and pollen contained in ancient mud to determine how Aboriginal Tasmanians shaped their surroundings. This is the earliest record of humans using fire to shape the Tasmanian environment.

Early human migrations from Africa to the southern part of the globe were well underway during the early part of the last ice age – humans reached northern Australia by around 65,000 years ago. When the first Palawa/Pakana (Tasmanian Indigenous) communities eventually reached Tasmania (known to the Palawa people as Lutruwita), it was the furthest south humans had ever settled.

These early Aboriginal communities used fire to penetrate and modify dense, wet forest for their own use – as indicated by a sudden increase in charcoal accumulated in ancient mud 41,600 years ago.

̽��ֱ��researchers say their results, reported in the journal Science Advances, could not only help us understand how humans have been shaping the Earth’s environment for tens of thousands of years, but also help understand the long-term Aboriginal-landscape connection, which is vital for landscape management in Australia today.

Tasmania currently lies about 240 kilometres off the southeast Australian coast, separated from the Australian mainland by the Bass Strait. However, during the last ice age, Australia and Tasmania were connected by a huge land bridge, allowing people to reach Tasmania on foot. ̽��ֱ��land bridge remained until about 8,000 years ago, after the end of the last ice age, when rising sea levels eventually cut Tasmania off from the Australian mainland.

“Australia is home to the world’s oldest Indigenous culture, which has endured for over 50,000 years,” said Dr Matthew Adeleye from Cambridge’s Department of Geography, the study’s lead author. “Earlier studies have shown that Aboriginal communities on the Australian mainland used fire to shape their habitats, but we haven’t had similarly detailed environmental records for Tasmania.”

̽��ֱ��researchers studied ancient mud taken from islands in the Bass Strait, which is part of Tasmania today, but would have been part of the land bridge connecting Australia and Tasmania during the last ice age. Due to low sea levels at the time, Palawa/Pakana communities were able to migrate from the Australian mainland.

Analysis of the ancient mud showed a sudden increase in charcoal around 41,600 years ago, followed by a major change in vegetation about 40,000 years ago, as indicated by different types of pollen in the mud.

“This suggests these early inhabitants were clearing forests by burning them, in order to create open spaces for subsistence and perhaps cultural activities,” said Adeleye. “Fire is an important tool, and it would have been used to promote the type of vegetation or landscape that was important to them.”

̽��ֱ��researchers say that humans likely learned to use fire to clear and manage forests during their migration across the glacial landscape of Sahul – a palaeocontinent that encompassed modern-day Australia, Tasmania, New Guinea and eastern Indonesia – as part of the extensive migration out of Africa.

“As natural habitats adapted to these controlled burnings, we see the expansion of fire-adapted species such as Eucalyptus, primarily on the wetter, eastern side of the Bass Strait islands,” said Adeleye.

Burning practices are still practiced today by Aboriginal communities in Australia, including for landscape management and cultural activities. However, using this type of burning, known as cultural burning, for managing severe wildfires in Australia remains contentious. ̽��ֱ��researchers say understanding this ancient land management practice could help define and restore pre-colonial landscapes.

“These early Tasmanian communities were the island’s first land managers,” said Adeleye. “If we’re going to protect Tasmanian and Australian landscapes for future generations, it’s important that we listen to and learn from Indigenous communities who are calling for a greater role in helping to manage Australian landscapes into the future.”

̽��ֱ��research was supported in part by the Australian Research Council.

Reference:
Matthew A Adeleye et al. ‘Landscape burning facilitated Aboriginal migration into Lutruwita/Tasmania 41,600 years ago.’ Science Advances (2024). DOI: 10.1126/sciadv.adp6579

Some of the first human beings to arrive in Tasmania, over 41,000 years ago, used fire to shape and manage the landscape, about 2,000 years earlier than previously thought.

Simon Haberle

Emerald Swamp, Tasmania

Yes

Planting trees in the Arctic could make global warming worse, not better, say scientists

sc604 — Thu, 07 Nov 2024 13:41:21 +0000

But, writing in the journal Nature Geoscience, an international group of scientists, led by the ̽��ֱ�� of Cambridge and the ̽��ֱ�� of Århus, argue that tree planting at high latitudes will accelerate, rather than decelerate, global warming.

As the climate continues to warm, trees can be planted further and further north, and large-scale tree-planting projects in the Arctic have been championed by governments and corporations as a way to mitigate the worst effects of climate change.

However, when trees are planted in the wrong places - such as normally treeless tundra and mires, as well as large areas of the boreal forest with relatively open tree canopies - they can make global warming worse.

According to lead author Assistant Professor Jeppe Kristensen from Aarhus ̽��ֱ�� in Denmark, the unique characteristics of Arctic and sub-Arctic ecosystems make them poorly suited for tree planting for climate mitigation.

“Soils in the Arctic store more carbon than all vegetation on Earth,” said Kristensen. “These soils are vulnerable to disturbances, such as cultivation for forestry or agriculture, but also the penetration of tree roots. ̽��ֱ��semi-continuous daylight during the spring and early summer, when snow is still on the ground, also makes the energy balance in this region extremely sensitive to surface darkening, since green and brown trees will soak up more heat from the sun than white snow.”

In addition, the regions surrounding the North Pole in North America, Asia and Scandinavia are prone to natural disturbances - such as wildfires and droughts - that kill off vegetation. Climate change makes these disturbances both more frequent and more severe.

“This is a risky place to be a tree, particularly as part of a homogeneous plantation that is more vulnerable to such disturbances,” said Kristensen. “ ̽��ֱ��carbon stored in these trees risks fuelling disturbances and getting released back to the atmosphere within a few decades.”

̽��ֱ��researchers say that tree planting at high latitudes is a prime example of a climate solution with a desired effect in one context but the opposite effect in another.

“ ̽��ֱ��climate debate is very carbon-focused because the main way humans have modified the Earth’s climate in the last century is through emitting greenhouse gases from burning fossil fuels,” said Kristensen. “But at the core, climate change is the result of how much solar energy entering the atmosphere stays, and how much leaves again – Earth’s so-called energy balance.”

Greenhouse gases are one important determinant of how much heat can escape our planet’s atmosphere. However, the researchers say that at high latitudes, how much sunlight is reflected back into space, without being converted into heat (known as the albedo effect), is more important than carbon storage for the total energy balance.

̽��ֱ��researchers are calling for a more holistic view of ecosystems to identify truly meaningful nature-based solutions that do not compromise the overall goal: slowing down climate change.

“A holistic approach is not just a richer way of looking at the climate effects of nature-based solutions, but it’s imperative if we’re going to make a difference in the real world,” said senior author Professor Marc Macias-Fauria, from the ̽��ֱ�� of Cambridge’s Scott Polar Research Institute.

However, the researchers recognise that there can be other reasons for planting trees, such as timber self-sufficiency, but these cases do not come with bonuses for climate mitigation.

“Forestry in the far North should be viewed like any other production system and compensate for its negative impact on the climate and biodiversity,” said Macias-Fauria. “You can’t have your cake and eat it, and you can’t deceive the Earth. By selling northern afforestation as a climate solution, we’re only fooling ourselves.”

So how can we moderate global warming at high latitudes? ̽��ֱ��researchers suggest that working with local communities to support sustainable populations of large herbivores, such as caribou, could be a more viable nature-based solution to climate change in Arctic and subarctic regions than planting millions of trees.

“There is ample evidence that large herbivores affect plant communities and snow conditions in ways that result in net cooling,” said Macias-Fauria. “This happens both directly, by keeping tundra landscapes open, and indirectly, through the effects of herbivore winter foraging, where they modify the snow and decrease its insulation capacity, reducing soil temperatures and permafrost thaw.”

̽��ֱ��researchers say it’s vital to consider biodiversity and the livelihoods of local communities in the pursuit of nature-based climate solutions.

“Large herbivores can reduce climate-driven biodiversity loss in Arctic ecosystems and remain a fundamental food resource for local communities,” said Macias-Fauria. “Biodiversity and local communities are not an added benefit to nature-based solutions: they are fundamental. Any nature-based solutions must be led by the communities who live at the front line of climate change.”

More about this story

Reference:
Jeppe Å Kristensen et al. ‘Tree planting is no climate solution at northern high latitudes.’ Nature Geoscience (2024). DOI: 10.1038/s41561-024-01573-4

Explore more discoveries, innovations and research on climate and nature at the ̽��ֱ�� of Cambridge: www.cam.ac.uk/climate-and-nature

Tree planting has been widely touted as a cost-effective way of reducing global warming, due to trees’ ability to store large quantities of carbon from the atmosphere.

Pierre Longnus via Getty Images

Emerald Lake, Yukon

Yes

Changemakers: Bhaskar Vira, Pro-Vice-Chancellor for Education and Environmental Sustainability

lw355 — Mon, 21 Oct 2024 08:50:53 +0000

Economist, researcher and educator, Bhaskar Vira is keeping faith with a life-long love for the natural world and a determination to tackle the climate and nature crises.

Building a more sustainable world

skbf2 — Thu, 19 Sep 2024 10:21:27 +0000

This longstanding partnership between Cambridge, Arup and the Ove Arup Foundation has made our world safer and more sustainable and changed the way professionals are taught.