Deep-Time Major Biological and Climatic Events vs. Global Changes: Progresses and Challenges
Introduction
Global change is reshaping Earth’s ecosystems at an unprecedented pace, profoundly influencing the evolution and distribution of life. Since the establishment of modern ecosystems approximately 540 million years ago, the Earth has experienced multiple climate extremes coupled with significant disruptions in the global carbon cycle. Understanding the triggers, processes, and biological responses to these deep-time climate events is crucial for predicting and managing current biodiversity shifts. However, bridging the gap between deep-time geological records and modern global changes remains a formidable challenge, primarily due to differences in time scales, the scarcity of high-resolution environmental proxies, and the lack of comprehensive biodiversity data across marine and terrestrial ecosystems.
Major Biological Events and Environmental Backgrounds
Extinction Events
- Ordovician End Extinction: Occurring around 445 million years ago, this event saw a significant decline in marine biodiversity, coinciding with a rapid cooling event (~5°C) and a sharp drop in carbon isotopes (~3‰).
- Permian-Triassic Mass Extinction: The most severe biotic crisis in Earth’s history, associated with rapid warming (~8-10°C), massive carbon isotope excursions (~5-8‰), and extensive volcanic activity from the Siberian Traps.
- Cretaceous-Paleogene Extinction: Linked to the Chicxulub impact and Deccan Traps volcanism, resulting in the demise of non-avian dinosaurs and significant changes in marine and terrestrial ecosystems.
Radiation Events
- Cambrian Explosion: Around 540 million years ago, the rapid diversification of multicellular organisms marked the emergence of modern animal phyla, occurring under warm climatic conditions.
- Ordovician Early Radiation: Following a period of gradual cooling, marine biodiversity increased, highlighting the role of stable environmental changes in fostering evolutionary radiations.
- Carboniferous-Permian Radiation: Spanning millions of years, this period was characterized by the expansion of terrestrial plants and marine invertebrates, coinciding with the onset of the Late Paleozoic Ice Age.
Controlling Factors of Biodiversity
Biotic Factors
Biological evolution and diversification are fundamental to biodiversity. Organisms adapt to stable environments through natural selection, but internal biological dynamics alone cannot fully explain the large-scale fluctuations in biodiversity observed in deep time.
Abiotic Factors
- CO2 and O2: Atmospheric CO2 and O2 levels are closely linked to climate and biotic evolution. Rapid changes in these gases, such as those associated with volcanic eruptions, can trigger extreme climate events and mass extinctions.
- Temperature: Temperature is a critical driver of species distribution and survival. However, historical data show that both extreme warmth and cold can support biodiversity, indicating that the rate of temperature change (rather than absolute temperature) is a key factor.
- Volcanic Activity: Large igneous provinces, such as the Siberian Traps and Deccan Traps, have been linked to mass extinctions through rapid greenhouse gas emissions and environmental perturbations.
Environmental Variability and Biological Responses
Recent studies highlight that the rate of environmental change (environmental variability) is a more critical factor than the absolute values of environmental parameters. Stable environments allow organisms to adapt gradually, fostering biodiversity, while rapid environmental shifts exceed ecological thresholds, leading to mass extinctions. For example, the Paleocene-Eocene Thermal Maximum (PETM) involved a rapid ~5-8°C warming over ~170,000 years, associated with significant carbon isotope changes, but the biotic response varied across ecosystems.
Challenges and Prospects
Current research faces several hurdles, including the lack of high-precision time scales, insufficient high-resolution environmental proxy data, and the absence of comprehensive biodiversity curves for both marine and terrestrial ecosystems. To address these, integrated studies combining deep-time geological records, modern climate models, and Earth system simulations are essential. Developing high-resolution Earth system models to simulate past and future climate events will provide insights into the mechanisms driving biodiversity changes and help anticipate future ecological responses.
Conclusion
The relationship between deep-time biological events and climate changes underscores the importance of environmental variability in shaping biodiversity. By integrating multi-disciplinary approaches and leveraging advanced modeling techniques, we can better understand the triggers of past extinctions and radiations, providing critical insights for mitigating current biodiversity loss and managing future global change.
Author Information
Shuzhong Shen¹*, Feifei Zhang¹, Wenqian Wang¹, Xiangdong Wang¹, Junxuan Fan¹, Jitao Chen², Bo Wang², Jian Cao¹, Shiling Yang³, Hua Zhang², Gaojun Li¹, Tao Deng⁴, Xianhua Li⁵, Jun Chen¹
- State Key Laboratory for Mineral Deposits Research, Frontiers Science Center for Critical Earth Material Cycling, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
*Corresponding author: szshen@nju.edu.cn
DOI
doi: 10.1360/TB-2023-0218
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