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Carboniferous rainforest collapse
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Carboniferous rainforest collapse
The Carboniferous rainforest collapse (CRC) was a minor extinction event that occurred around 305 million years ago in the Carboniferous period. The event occurred at the end of the Moscovian and continued into the early Kasimovian stages of the Pennsylvanian (Upper Carboniferous).
It altered the vast coal forests that covered the equatorial region of Euramerica (Europe and North America). This event may have fragmented the forests into isolated refugia or ecological "islands", which in turn encouraged dwarfism and, shortly after, extinction of many plant and animal species. Following the event, coal-forming tropical forests continued in large areas of the Earth, but their extent and composition were changed.
In the Carboniferous, the great tropical rainforests of Euramerica supported towering lycopodiophyta, a heterogeneous mix of vegetation, as well as a great diversity of animal life: giant griffinflies, millipedes, blattopterans, smaller amphibians, and the first amniotes.
The rise of rainforests in the Carboniferous greatly altered the landscapes by eroding low-energy, organic-rich anastomosing (braided) river systems with multiple channels and stable alluvial islands. The continuing evolution of tree-like plants increased floodplain stability (less erosion and movement) by the density of floodplain forests, the production of woody debris, and an increase in complexity and diversity of root assemblages.
Collapse occurred through a series of step changes. First there was a gradual rise in the frequency of opportunistic ferns in late Moscovian times. This was followed in the earliest Kasimovian by a major, abrupt extinction of the dominant lycopsids and a change to tree fern-dominated ecosystems. This is confirmed by a 2011 study showing that the presence of meandering and anabranching streams, occurrences of large woody debris, and records of log jams decrease significantly at the Moscovian-Kasimovian boundary. Rainforests were fragmented, forming shrinking 'islands' further and further apart, and in latest Kasimovian time, rainforests vanished from the fossil record. Little mixing of different plant assemblages occurred throughout this transition; floral assemblages were highly discrete and conservative and gave way to new ones without any transitional floras intermediate in composition with regards to the preceding one and succeeding one.
The fossil record of insects can be difficult to study, due to the generally smaller and more delicate nature of their bodies. One study tabulate the rates of origination and extinction of over 600 terrestrial and freshwater animal families. Their stratigraphic ranges spanned a geologic interval from the middle Paleozoic biotic invasion of the land to the Permian–Triassic extinction event. Insects comprise more than half of the sampled families, most of which are from tropical Euramerica. This study found a Late Pennsylvanian extinction pulse that reflects drying climates and the transition of lycopod to tree fern-dominated land floras.
Before the collapse, vertebrate animal species distribution was very cosmopolitan, with the same species existing across tropical Pangaea. After the collapse, each surviving rainforest 'island' developed its own unique mix of species. Many amphibian species became extinct, while the ancestors of reptiles and mammals diversified into more species after the initial crisis. These patterns are explained by the theory of insular biogeography, a concept that explains how evolution progresses when populations are restricted into isolated pockets. This theory was originally developed for oceanic islands, but it can be applied equally well to any other ecosystem that is fragmented, only existing in small patches and surrounded by another unsuitable habitat.
According to this theory, the initial impact of habitat fragmentation is devastating, with most life dying out quickly from lack of resources. Then, as surviving plants and animals reestablish themselves, they adapt to their restricted environment to take advantage of the new allotment of resources, and diversify. After the CRC, each pocket of life evolved in its own way, resulting in a unique species mix that ecologists call "endemism". A 2018 paper challenged this theory, however, finding evidence for increased cosmopolitanism rather than endemism following the demise of Carboniferous rainforests.
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Carboniferous rainforest collapse
The Carboniferous rainforest collapse (CRC) was a minor extinction event that occurred around 305 million years ago in the Carboniferous period. The event occurred at the end of the Moscovian and continued into the early Kasimovian stages of the Pennsylvanian (Upper Carboniferous).
It altered the vast coal forests that covered the equatorial region of Euramerica (Europe and North America). This event may have fragmented the forests into isolated refugia or ecological "islands", which in turn encouraged dwarfism and, shortly after, extinction of many plant and animal species. Following the event, coal-forming tropical forests continued in large areas of the Earth, but their extent and composition were changed.
In the Carboniferous, the great tropical rainforests of Euramerica supported towering lycopodiophyta, a heterogeneous mix of vegetation, as well as a great diversity of animal life: giant griffinflies, millipedes, blattopterans, smaller amphibians, and the first amniotes.
The rise of rainforests in the Carboniferous greatly altered the landscapes by eroding low-energy, organic-rich anastomosing (braided) river systems with multiple channels and stable alluvial islands. The continuing evolution of tree-like plants increased floodplain stability (less erosion and movement) by the density of floodplain forests, the production of woody debris, and an increase in complexity and diversity of root assemblages.
Collapse occurred through a series of step changes. First there was a gradual rise in the frequency of opportunistic ferns in late Moscovian times. This was followed in the earliest Kasimovian by a major, abrupt extinction of the dominant lycopsids and a change to tree fern-dominated ecosystems. This is confirmed by a 2011 study showing that the presence of meandering and anabranching streams, occurrences of large woody debris, and records of log jams decrease significantly at the Moscovian-Kasimovian boundary. Rainforests were fragmented, forming shrinking 'islands' further and further apart, and in latest Kasimovian time, rainforests vanished from the fossil record. Little mixing of different plant assemblages occurred throughout this transition; floral assemblages were highly discrete and conservative and gave way to new ones without any transitional floras intermediate in composition with regards to the preceding one and succeeding one.
The fossil record of insects can be difficult to study, due to the generally smaller and more delicate nature of their bodies. One study tabulate the rates of origination and extinction of over 600 terrestrial and freshwater animal families. Their stratigraphic ranges spanned a geologic interval from the middle Paleozoic biotic invasion of the land to the Permian–Triassic extinction event. Insects comprise more than half of the sampled families, most of which are from tropical Euramerica. This study found a Late Pennsylvanian extinction pulse that reflects drying climates and the transition of lycopod to tree fern-dominated land floras.
Before the collapse, vertebrate animal species distribution was very cosmopolitan, with the same species existing across tropical Pangaea. After the collapse, each surviving rainforest 'island' developed its own unique mix of species. Many amphibian species became extinct, while the ancestors of reptiles and mammals diversified into more species after the initial crisis. These patterns are explained by the theory of insular biogeography, a concept that explains how evolution progresses when populations are restricted into isolated pockets. This theory was originally developed for oceanic islands, but it can be applied equally well to any other ecosystem that is fragmented, only existing in small patches and surrounded by another unsuitable habitat.
According to this theory, the initial impact of habitat fragmentation is devastating, with most life dying out quickly from lack of resources. Then, as surviving plants and animals reestablish themselves, they adapt to their restricted environment to take advantage of the new allotment of resources, and diversify. After the CRC, each pocket of life evolved in its own way, resulting in a unique species mix that ecologists call "endemism". A 2018 paper challenged this theory, however, finding evidence for increased cosmopolitanism rather than endemism following the demise of Carboniferous rainforests.
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