The Upcoming Ice Age: Where Will Animal Species Find Refuge?

Prospective map of terrestrial and oceanic refuges during the next glaciation — What will Earth look like in 50,000 years, with advancing glaciers, expanding tundras, last refuges for wildlife, and still fertile oceans?
Image source: astronoo.com (new window)

Scientific Summary

The question "When should the next ice age begin?" is linked to the Milanković orbital cycles: without human influence, a new glaciation would have started in ~10,000 to 11,000 years. However, the rise in anthropogenic CO₂ delays this threshold far beyond, to ~50,000 years or more. The current climate prevents the accumulation of summer snow, a necessary condition for the growth of ice sheets.

Today, only a few regions are truly uninhabitable (Antarctica, central Sahara, interior Greenland, high mountain ranges, etc.). Habitable lands represent ≈135 million km² out of ≈149 million km² of emerged lands. Based on the Last Glacial Maximum (LGM, ~21,000 years ago), it is possible to identify future viable spaces for biodiversity during the next glaciation. Terrestrial refuges will be mainly located in the southern temperate regions (Mediterranean basin, southern Africa, Australia, South America), humid tropical zones, and emerged continental plateaus (Beringia, Sunda).

What Will Be the Refuges for Life During the Next Glaciation?

In ~50,000 years, if the natural cycles of Milanković resume their course, Earth will experience a new ice age comparable to the Last Glacial Maximum. Glaciated zones will cover Canada, the northern United States, Scandinavia, and the Alps. Terrestrial life will concentrate in refuges: Mediterranean basin, sub-Saharan Africa, Southeast Asia, Beringia, and coastal zones of the Southern Hemisphere. The oceans will maintain biological productivity in marine glacier fjords and coastal upwelling zones, where deep nutrients rise to the surface. Latitudinal migration, physiological adaptation, and ecosystem resilience will be key to survival, but the human footprint (fragmentation, pollution, warming) could deeply alter these refuges and the ability of species to establish themselves there.

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The Cycle of Glaciations

Earth's climatic history is marked by alternations between glacial and interglacial periods, whose main trigger is astronomical. The Milanković cycles describe the periodic variations in solar insolation received by the planet, due to the combined effect of three orbital parameters: the eccentricity of Earth's orbit (~100,000-year cycle), the obliquity or tilt of the rotational axis (~41,000-year cycle), and the precession of the equinoxes (~19,000 to 23,000-year cycle). These variations modify the seasonal and latitudinal distribution of solar energy, directly influencing the formation and melting of ice sheets. When the summers in the Northern Hemisphere are cold enough for snow not to melt completely, it accumulates and compacts into ice, initiating a glaciation.

An ice age is characterized by a major expansion of polar and continental ice sheets (ice caps), a drop in sea level of about 120 meters (due to water being locked up as ice), a global cooling of 4 to 8 °C on average, and a profound modification of ocean currents, particularly the Atlantic Meridional Overturning Circulation (AMOC). These transformations force species to adapt or move.

Estimate of Habitable Lands During the Next Ice Age

Based on the current surface area of habitable lands (≈135 million km²) and the likely expansion of ice sheets and periglacial zones during a future glaciation, it can be estimated that the surface area of habitable lands will be ≈100 to 110 million km² (a reduction of about 20 to 40% compared to the current situation).

Major Glaciations in Earth's Recent History

Chronology of Major Quaternary Glaciations (Marine Isotope Stages)
Name of the Era / Glacial Period	Approximate Interval	Heavily Glaciated Regions	Scientific Remarks
Last Glacial Maximum (LGM)	~26,000 – 19,000 years ago	Laurentide (North America), Fennoscandia (Northern Europe), Alpine and Andean ice caps	Peak of the last Quaternary glaciation; sea level ~120 m lower, vast cold steppes in Eurasia.
Penultimate Glacial Period (MIS 6)	~190,000 – 130,000 years ago	North America, Northern Europe, Greenland, Antarctica	Significant glaciation preceding the Eemian interglacial; extensive ice sheets but different configuration from the LGM.
Glaciation of MIS 8	~300,000 – 250,000 years ago	High latitudes of the Northern Hemisphere and Antarctica	Marked cold phase in marine isotope records; alternation with milder interglacials.
Glaciation of MIS 10	~370,000 – 330,000 years ago	North American and Eurasian ice sheets, Antarctica	Deep glaciation of the Middle Quaternary, well visible in marine sediment cores.
Glaciation of MIS 12	~480,000 – 430,000 years ago	Northern Hemisphere (continental ice sheets), Antarctica	One of the most intense glaciations of the Quaternary, with maximal extension of ice sheets in the Northern Hemisphere.
Glaciation of MIS 16	~650,000 – 620,000 years ago	High northern latitudes and Antarctica	Ancient Quaternary glaciation, identified mainly by oxygen isotope variations in the oceans.

Projection at 50,000 Years: Viable Terrestrial Zones

In a "natural" climate scenario, the next glaciation should intensify from ~30,000 years and reach a maximum around 50,000 years. Paleoclimate models suggest a configuration comparable to the LGM, but with differences due to the current continental configuration and the legacy of anthropogenic warming.

Non-Glaciated Temperate Zones

The mid-latitudes of the Northern Hemisphere, between 30° and 50°, will remain partially ice-free. In Southern Europe (Iberian, Italian, and Balkan peninsulas) and around the Mediterranean basin, cold steppe or boreal forest conditions will prevail, but with more humid refuges at altitude. In South Asia, the Himalayan range and the Tibetan massifs will offer high-altitude refuges, while the Ganges plains could remain relatively temperate.

Tropical Regions

Tropical zones (Central America, Amazon basin, Central Africa, Southeast Asia) will be among the most thermally stable regions, although they will experience significant drying and a reduction of humid forests in favor of savannas and open forests. The Amazon rainforest will contract into refuges, while African savannas will expand. Tropical mountain zones (Andes, Kilimanjaro, New Guinea) will play a crucial role as refuges for high-altitude species.

Exposed Continental Shelves

The drop in sea level (~120 m) will expose vast territories. In Asia, the Sunda shelf will connect the Sunda Islands to the Malay Peninsula, creating a vast area of savanna and open forest, a refuge for many Asian species. Beringia will reappear, offering a corridor between Asia and North America. Similarly, the Australian shelf (Sahul) will connect Australia, Tasmania, and New Guinea.

Cold Deserts and Periglacial Steppes

Around the ice sheets, a wide belt of periglacial steppes (similar to the mammoth steppe of Beringia) and cold deserts (loess) will cover much of Central Europe, Siberia, and the North American plains. These environments, although poor in trees, are extremely productive in grasses and herbs, supporting a megafauna of herbivores. The southernmost zones of these steppes (e.g., Hungary, Ukraine, American Great Plains) will constitute refuges for large mammals.

Viable Oceanic Habitats Despite Cooling

The ocean will undergo major transformations: drop in sea level, changes in currents, cooling of surface waters, expansion of sea ice. However, some areas will remain biologically active.

Sea Level Drop and New Lands

The exposure of continental shelves will reduce the surface area of epicontinental seas (e.g., South China Sea, North Sea), but will create new coastal habitats and lagoons, rich in nutrients.

Shift in Marine Productivity

Marine primary productivity (phytoplankton) will concentrate in upwelling zones (rising of deep, nutrient-rich waters), mainly along the west coasts of continents (California, Peru, Morocco, Namibia) and in the Southern Ocean. Glaciations favor upwellings due to the intensification of trade winds.

Role of Ocean Currents

Changes in the AMOC (slowdown or partial shutdown) will reduce heat transport to the North Atlantic, cooling European waters and limiting productivity in northern seas. However, fjords fed by marine glaciers (directly ending in the sea) could become highly productive zones. Indeed, the plumes of meltwater from marine glaciers cause a local upwelling (rising of deep, nutrient-rich waters), which supports high primary production, as observed in Greenland. This phenomenon is called the "fertilizing effect of marine glaciers."

Biologically Active Oceanic Zones

The oceanic zones that will remain productive are therefore:

Coastal upwelling zones (year-round productivity).
Fjords with marine glaciers (e.g., Greenland, Patagonia, Svalbard), where nutrient input maintains summer phytoplankton blooms.
Seasonal ice shelves (Antarctica, Arctic), rich in sea ice that hosts communities of diatoms and krill.
Ridges and submarine platforms (e.g., Dogger Bank in the exposed North Sea), zones of mixing and nutrients.

Impacts on Living Species and Survival Strategies

The response of species to the next glaciation will partly repeat the patterns observed during the LGM, but in a new context marked by human impact.

Survival Strategies

Latitudinal Migration: Species from temperate zones will migrate south (Northern Hemisphere) or north (Southern Hemisphere). Trees and forests will move hundreds of kilometers toward the equator.
Physiological Adaptation: Some species will develop cold-resistant phenotypes (morphology, metabolism, cryoprotection). Small mammals (e.g., Arctic ground squirrels) could survive through hibernation.
Expansion into Refuges: Climate refuges will be areas of biodiversity concentration, where interactions between species will intensify.

Vulnerable and Resilient Species

Vulnerable: Species with low dispersal capacity (plants with heavy seeds, reptiles, amphibians), cold habitat specialists that may be trapped (e.g., mountain species without altitudinal refuge), and species of large tropical forests if fragmentation is too severe.
Resilient: Generalist species (e.g., crows, rats, foxes), steppe herbivores (bison, horses, camels), and marine planktonic organisms with resistance stages (cysts, spores).

Where Will Humans Live in This Glacial World?

Unlike wild species, humans will not depend solely on natural climate refuges: technology, agriculture, and social organization will provide additional room for maneuver. Physical constraints will remain decisive, particularly access to arable land, fresh water, and energy.

The most favorable regions for human settlement will largely coincide with the biodiversity refuges already identified (Mediterranean basin, South Asia, sub-Saharan Africa, Central America), between 20° and 45° latitude. This is already the pattern observed during the Last Glacial Maximum, where human archaeological sites are concentrated precisely in these areas. The current major cereal plains (North America, Northern Europe) will become periglacial steppes unsuitable for crops, while new arable lands will appear on continental shelves exposed by the drop in sea level (~120 m).

This scenario remains conditioned by technology, which could allow the occupation of larger regions than those estimated.

Factors Determining Human Habitability During a Future Glaciation
Factor	Effect During Glacial Period	Consequence for Human Settlement
Average Temperature	Drop of 4 to 8 °C	Contraction of habitable zones toward mid-latitudes and tropics
Sea Level	Drop of about 120 m	Exposure of new coastal lands, obsolescence of current ports
Precipitation	Regional redistribution (drying or humidification depending on areas)	Displacement of agricultural zones, appearance of new inland lakes
Extent of Ice Sheets	Expansion over North America and Northern Europe	Abandonment of currently most densely populated regions of the Northern Hemisphere
Energy and Technological Resources	No direct climate-related change	Allow occupation of climatically marginal zones, provided stable access to resources

Prospective Textual Mapping of World Regions

The configuration of Earth in ~50,000 years (if glaciation occurs) could be described as follows:

Categories of Zones During the Next Glaciation
Category	Regions Concerned	Characteristics
Glaciated Zones	Canada, northern United States, Greenland, Scandinavia, Iceland, Alps, Urals, Patagonia, Antarctica (expansion)	Thick ice sheets (several km), near-total absence of life, a few bare refuges (nunataks).
Periglacial Zones (Cold Steppes, Loess Deserts)	Central Europe (Germany, Poland, Western Russia), American plains (Midwest), Southern Siberia, Northern China, Argentina (Pampas)	Open landscapes, dominated by grasses and herbs, with frozen soils (permafrost), high wind activity (loess deposits).
Terrestrial Biological Refuges	Mediterranean basin, Iberian Peninsula, Italy, Balkans, East Africa, Southern Africa, Southeast Asia (Sunda), Central America, Andes, Himalayas, Beringia, Tasmania, New Zealand, Coastal California	Mixed temperate forests, humid savannas, humid tropical forests (in low-altitude zones), mountainous areas with microclimates, refuges for megafauna.
Productive Oceanic Zones	Coastal upwellings (California, Peru, Morocco, Namibia, Senegal), fjords of Greenland and Patagonia, Bering Sea, Antarctic ice shelf, Dogger Bank (exposed North Sea)	Upwelling of deep waters, nutrient input, phytoplankton blooms, rich marine food chains (fish, marine mammals, birds).

Conclusion: What Future for Life in a Glacial World?

The next ice age, if it occurs, will not mark the end of life on Earth, but rather a major redistribution of its presence. In about 50,000 years, humanity could adapt and live comfortably in a glacial world, thanks to technologies that are currently unimaginable. Abundant energy (nuclear fusion, geothermal), controlled habitats (domes or underground structures), climate-independent agriculture, advanced biotechnologies, and AI-assisted robotics for logistics could transform this icy world into a cold but entirely livable environment, even conducive to human prosperity.

Scientific References

FAQ: Understanding Refuges During Glaciations

What is a biological refuge (refugium) during a glaciation?

A biological refuge is a geographical area where climatic conditions have remained relatively mild during a glacial period, allowing species to survive while they disappeared from surrounding regions. These refuges are often sheltered valleys, coastal zones, mountainous regions, or humid tropical forests. They are essential for post-glacial recolonization.

What were the main refuges during the last glaciation?

The main terrestrial refuges were located in Southern Europe (Iberian, Italian, Balkan peninsulas), North America (southeastern United States, California coast), Asia (Beringia, Himalayas, Southeast Asia), and sub-Saharan Africa (Great Lakes region, South Africa).

Why are marine glaciers important for marine productivity?

Marine glaciers (which end directly in the sea) cause plumes of meltwater that bring deep, nutrient-rich waters to the surface. This phenomenon, called glacial upwelling, fertilizes the sea surface and supports high phytoplankton productivity, even in summer, which is not the case in fjords bordered by land glaciers.

Is the next ice age certain?

No, human activity could delay or prevent it. Massive CO₂ emissions (greenhouse gases) are warming the planet. According to researcher Frerk Pöppelmeier, "if we continue to emit CO₂, it is possible that we will never have another ice age in the foreseeable future." Natural orbital parameters are in place, but anthropogenic greenhouse effect opposes them.

How do plant species migrate during a glaciation?

Plant species migrate mainly through seed dispersal (wind, animals) and gradual expansion of populations toward milder zones. Trees, for example, can move several hundred meters per year on average, but species with heavy seeds (such as beech or oak) are slower and may be trapped if glaciation is rapid. Mountain refuges often allow species to survive at altitude rather than migrating long distances.