Why Climate Was the Biggest Driver of Dinosaur Diversity

Dinosaurs didn’t just evolve in a vacuum—they thrived, adapted, and radiated into countless forms because of one powerful force: climate. From lush tropical swamps to arid deserts and polar forests, shifting climates across millions of years created both challenges and opportunities that shaped dinosaur evolution. Temperature swings, rising and falling sea levels, and changes in vegetation dictated which species survived, where they migrated, and how they diversified into everything from towering sauropods to nimble raptors. In this article, we’ll uncover why climate was the biggest driver of dinosaur diversity, showing how Earth’s ever-changing environment sculpted the reign of these prehistoric giants.

The Great Climate Catalyst of the Triassic-Jurassic Boundary

Two hundred and one million years ago, the Earth got so hot that it caused a mass extinction of animals and other animate beings. For dinosaurs on the other hand, this climate change was actually beneficial: Their populations started growing and they expanded their habitat. This wasn’t just any ordinary warming period – it was a planetary transformation that would set the stage for continued dinosaur dominance.

The end-Triassic extinction eliminated some 76 percent of all marine and terrestrial species and about 20 percent of all taxonomic families. In fact, many authorities maintain that the end-Triassic mass extinction on land opened ecological niches that were filled relatively quickly by dinosaurs. Think of it like nature’s ultimate reshuffling of the deck – and dinosaurs were dealt the winning hand.

When Earth Became a Greenhouse Paradise

The climate during dinosaur reign was nothing like our modern world. In general, the climate of the Cretaceous Period was much warmer than at present, among the warmest periods during the Phanerozoic Eon. The climate was also more equable in that the temperature difference between the poles and the Equator was about one-half that of the present.

Temperatures were so high that champsosaurs (crocodile-like reptiles) lived as far north as the Canadian Arctic, and warm-temperature forests thrived near the South Pole. During the Cretaceous greenhouse periods, polar regions were much warmer than today. Imagine polar bears replaced by crocodiles – that’s how dramatically different our planet was back then.

The Sauropod Success Story

Sauropods were really fussy from the get-go: later in their evolution they continue to stay in warmer areas and avoid polar regions. These long-necked giants weren’t just random evolutionary experiments – they were climate specialists who knew exactly what they wanted.

Sauropod-like dinosaurs, which became the giant herbivore species of the later Jurassic like Diplodocus and Brachiosaurus, were able to thrive and expand across new territories as the planet warmed up after the extinction event, 201 million years ago. They showed how the sauropods, and sauropod-like animals, with their long tails and necks and small heads, were the runaway success story of a turbulent period of evolution.

Competition Myth Debunked

For decades, scientists believed dinosaurs outcompeted other animals to reach dominance. Recent research tells a completely different story. What we see in the data suggests that instead of dinosaurs being outcompeted by other large vertebrates, it was variations in climate conditions that were restricting their diversity. But once these conditions changed across the Triassic-Jurassic boundary, they were able to flourish.

Climate change, rather than competition, played a key role in the ascendancy of dinosaurs through the Late Triassic and Early Jurassic periods. According to new research, changes in global climate associated with the Triassic-Jurassic mass extinction — which wiped out many large terrestrial vertebrates such as the giant armadillo-like aetosaurs — actually benefitted the earliest dinosaurs. It’s like discovering that the tortoise didn’t win the race through steady persistence, but because the weather suddenly favored tortoises over hares.

The Volcanic Trigger Behind Dinosaur Rise

Over a relatively short period of time, massive volcanic eruptions from a large region known as the Central Atlantic Magmatic Province (CAMP) spewed forth huge amounts of lava and gas, including carbon dioxide, sulfur and methane. This sudden release of gases into the atmosphere may have created intense global warming and acidification of the oceans that ultimately killed off thousands of plant and animal species.

Cold periods induced by volcanic ejecta clouding the atmosphere might have favoured endothermic animals, with dinosaurs, pterosaurs, and mammals being more capable at enduring these conditions than large pseudosuchians due to insulation. The very catastrophe that destroyed other life forms became dinosaurs’ ticket to success.

Climate Zones Shift the Game

While the climate near the equator in the Late Triassic was much too warm for early dinosaur species, when the climate zones shifted in the early Jurassic, this allowed dinosaur species’ population to flourish and expand to new areas that were previously inaccessible. It’s fascinating how a planetary climate shift literally opened new territories for exploration and colonization.

The Early Triassic world wasn’t immediately welcoming to dinosaurs. They had to wait for their moment – and that moment came when volcanic activity reshuffled the entire climate system. All Triassic archosaurs, apart from dinosaurs, pterosaurs and crocodiles, went extinct. This opened up many of the environments that the archosaurs had occupied, paving the way for the surviving dinosaurs to take their place, while the small mammalian relatives still scurried around the forest floors.

The Decline: When Climate Turned Against Giants

Climate wasn’t just a friend to dinosaurs – it could also be their enemy. Despite the consensus that the impact of an asteroid in the Yucatán Peninsula (Chicxulub, Mexico) and its resulting environmental destruction is the causal mechanism for dinosaur extinction, there is a long-lived debate on whether the dinosaur extinction was geologically abrupt or more gradual. The gradual hypothesis supports a decline in diversity over the much longer timescale of hundreds of thousands to even tens of millions of years.

We investigate the influence of ecological and physical factors, and find that the decline of dinosaurs was likely driven by global climate cooling and herbivorous diversity drop. The latter is likely due to hadrosaurs outcompeting other herbivores. Even among dinosaurs, climate shifts created winners and losers.

Regional Climate Stories Tell Different Tales

Through a comprehensive analysis of sedimentary facies, variations in dinosaur fossil populations, and global climate records within an integrated chronological framework, we propose that the dinosaurs in the Shanyang Basin either migrated away or faced extinction during the last 0.4 million years of the Cretaceous due to a decline in habitability driven by climate changes. This study illuminates the causal relationship between dinosaur evolution and local climate fluctuations, offering valuable insights into the mechanisms underlying their evolutionary responses to environmental shifts.

As precipitation and temperature increased, the presence of dinosaur fossils gradually declined. We propose that rising temperatures and reduced availability of suitable nesting sites, influenced by increased precipitation, may have prompted dinosaurs in the Shanyang Basin to migrate in search of more hospitable habitats or face extinction. It’s a reminder that even small regional changes could have dramatic consequences for these giants.

Temperature Variations Drive Evolutionary Innovation

The global mean temperature experienced a long-term decline during the latest Cretaceous (∼ 75–66 Ma). However, multiple short-term warming intervals were also found in marine records during this period. These temperature swings weren’t just background noise – they were evolutionary catalysts.

The geographical distribution of abelisaurids in South America was influenced by climatic conditions. Different dinosaur groups evolved specialized adaptations for specific climate conditions, creating the incredible diversity we see in the fossil record.

The Modern Research Revolution

This study now has brought together data concerning all dinosaur species including paleogeographical information on fossil distribution, spatially-explicit general climate models and evolutionary tree-based statistical analyses to explore the links between dinosaur diversity and climate. For their research, the scientists compared models of prehistoric global climate conditions such as temperature and rainfall at the different habitats of dinosaurs back then.

Modern technology allows us to recreate ancient climates with unprecedented accuracy. In 2006, workers on the SK project, an ambitious terrestrial paleoclimatic and paleoenvironmental research effort in China’s Songliao Basin, began drilling through the basin’s rocks to obtain the first complete record of the terrestrial Cretaceous climate. The Songliao Basin preserves a continuous and complete terrestrial record of the Cretaceous.

Climate and Size: Breaking the Rules

We find no evidence for Bergmann’s rule in Mesozoic dinosaurs or mammaliaforms, the ancestors of extant homeothermic birds and mammals. When our model is applied to thousands of extant dinosaur (bird) and mammal species, we find that body size evolution remains independent of latitude. This discovery challenges long-held assumptions about how climate influences animal size.

Data from fossil records and climate models show that extinct mammals and dinosaurs (including extinct birds) did not get bigger with cooling temperatures. These two groups spread to every corner of the Earth, with dinosaurs diversifying into a wider range of sizes – from small flying birds to some of the largest terrestrial animals to exist. Dinosaurs played by their own rules when it came to climate adaptation.

Lessons for Our Climate Future

In this effort to project future climate scenarios, it is invaluable to investigate times in the geologic past when pCO2 levels and temperatures were higher than today because these are the best natural analogues that we have to provide reference points for the future. One such time of interest is the Cretaceous (145.5 million to 66.0 million years ago), when atmospheric conditions created an intense “greenhouse” climate on the planet.

A 2024 paleoclimate reconstruction named PhanDA found a strong correlation between temperature and carbon dioxide during the Paleozoic and the Cenozoic but did not find a similarly strong link during the age of the dinosaurs. So, the precise cause of the Cretaceous Hot Greenhouse will need continued research, but the fossils indicate a very warm planet.

The Continuing Climate Detective Story

Every fossil tells a climate story, and scientists are still piecing together this massive puzzle. Based on the analysis of the global dinosaur fossil database and paleoclimatic records, it has been suggested that global climate changes significantly influenced the evolution and extinction of dinosaurs. New discoveries continue to reveal how intimately connected dinosaur diversity was to Earth’s changing climate.

Climate change appears to have been really important in driving the evolution of early dinosaurs. What we want to do next is use the same techniques to understand the role of climate in the next 120 million years of the dinosaur story. We’re living through our own climate transformation – understanding how dinosaurs navigated theirs could provide crucial insights for our future.

The story of dinosaur diversity isn’t just about fierce predators and gentle giants. It’s about how life responds to planetary change, how opportunity emerges from catastrophe, and how climate shapes the very fabric of evolution. These ancient climate-driven transformations remind us that Earth’s climate system has always been dynamic, powerful, and utterly transformative.

What would today’s dinosaur equivalent look like in our warming world – and are we witnessing similar climate-driven evolutionary changes happening right now?