Carboniferous Rainforest Collapse

Carboniferous Rainforest Collapse

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The Carboniferous Rainforest Collapse (CRC) was an extinction event
Extinction event
An extinction event is a sharp decrease in the diversity and abundance of macroscopic life. They occur when the rate of extinction increases with respect to the rate of speciation...

 that occurred around 305 million years ago in the Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

 period). Vast coal forest
Coal forest
Coal forests were the vast swathes of wetlands that extended over much of the tropical land areas during late Carboniferous and Permian times. These forests got their name because they accumulated enormous deposits of peat which later changed into coal...

s (so called because the compacted remains of the dense vegetation formed coal seams) covered the equatorial region of Euramerica
Euramerica was a minor supercontinent created in the Devonian as the result of a collision between the Laurentian, Baltica, and Avalonia cratons .300 million years ago in the Late Carboniferous tropical rainforests lay over the equator of Euramerica...

 (Europe and America). Climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

 devastated tropical rainforest
Tropical rainforest
A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator . This ecosystem experiences high average temperatures and a significant amount of rainfall...

s, fragmenting the forests into isolated 'islands' and causing the extinction of many plant and animal species. The change was abrupt, happening during the Moscovian
Moscovian, deriving from Moscow, the capital of Russia, can have the following meanings:*An inhabitant of Moscow.*In stratigraphy:**Moscovian , an ICS stage in the Carboniferous;**Moscovian , a regional stage in the Pleistocene....

 and Kasimovian
The Kasimovian is an geochronologic age or chronostratigraphic stage in the ICS geologic timescale. It is the third stage in the Pennsylvanian , lasting from 306.5 ± 1.0 to 303.9 ± 0.9 Ma. The Kasimovian stage follows the Moscovian and is followed by the Gzhelian.-Name and definition:The Kasimovian...

 stages of the Pennsylvanian
The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...


Extinction Patterns

In the Carboniferous, the great tropical rainforests of Euramerica
Euramerica was a minor supercontinent created in the Devonian as the result of a collision between the Laurentian, Baltica, and Avalonia cratons .300 million years ago in the Late Carboniferous tropical rainforests lay over the equator of Euramerica...

 supported towering lycopsids, a heterogeneous mix of vegetation, as well as a great diversity of animal life: giant dragonflies, millipedes, cockroaches, amphibians, and the first reptiles.


The rise of rainforests in the Carboniferous greatly altered the landscapes by creating low-energy, organic-rich anastomosing
An anastomosis is the reconnection of two streams that previously branched out, such as blood vessels or leaf veins. The term is used in medicine, biology, mycology and geology....

 river systems with multiple channels and stable alluvial islands. The continuing evolution of tree-like plants increased floodplain stability 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 treefern dominated ecosystems. This is confirmed by a recent study has shown that the presence of braided, meandering, and branching rivers, 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.


Before the collapse, terrestrial invertebrates were diverse and included annelids, molluscs, and arthropods,including giant arthropleurids. Most were detritivorous, eating 'litter' off of the forest floor, however, some had evolved herbivorous and predatory forms.


Before the extinction event, terrestrial vertebrates were predominantly amphibians and a few basal amniotes (‘reptiles’). Amphibians were tied to waterside habitats and were primarily piscivores, though a few had evolved insectivory.


Before the collapse, animal species distribution was very cosmopolitan: the same species existed everywhere across tropical Pangaea
Pangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....

, but after the collapse each surviving rainforest island developed its own unique mix of species. Many amphibian species became extinct while reptiles diversified into more species after the initial crisis. These patterns are explained by the theory of island biogeography
Island biogeography
Island biogeography is a field within biogeography that attempts to establish and explain the factors that affect the species richness of natural communities. The theory was developed to explain species richness of actual islands...

, a concept that explains how evolution progresses when populations are restricted into isolated pockets. This theory was originally developed for oceanic islands but can be applied equally to any other ecosystem that is fragmented, only existing in small patches, surrounded by another 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 Carboniferous Rainforest Collapse, each pocket of life evolved in its own way, resulting in a unique species mix which ecologists term endemism.

In the sea

A large portion of marine life died out including the microscopic diatoms and radiolarians. Their skeletons now form thick layers of rock like Britain's White Cliffs of Dover. When a mass extinction takes places, these things settle into under sea canyons, they are carried by currents into eddies and are washed up on shores in different places. Then, under proper conditions with the right amount of pressure they can turn into our fossil fuels.


This sudden collapse affected several large groups, labyrinthodont amphibians were particularly devastated, while the first reptiles fared better, being ecologically adapted to the drier conditions that followed. Amphibians must return to water to lay eggs; in contrast, reptiles - whose amniote
The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes...

 eggs have a membrane ensuring gas exchange out of water and can therefore be laid on land - were better adapted to the new conditions. Reptiles acquired new niches at a faster rate than before the collapse and at a much faster rate than amphibians. They acquired new feeding strategies including herbivory and carnivory, previously only having been insectivores and piscivores.


Atmospheric levels of carbon dioxide crashed to one of its all time global lows in the Pennsylvanian and early Permian.


There are several hypotheses about the nature and cause of the Carboniferous Rainforest Collapse, some of which include climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

. Specifically, at this time climate became cooler and drier, this is reflected in the rock record as the Earth entered into a short, intense ice age. Sea levels dropped by a hundred metres and glacial ice covered most of the southern continent of Gondwana.

The cooler, drier climate conditions were not favourable to the growth of rainforests and much of the biodiversity within them. Rainforests shrank into isolated patches, these islands of rainforest were mostly confined to wet valleys further and further apart. Little of the original lycopsid rainforest biome survived this initial climate crisis, only to survive in isolated refugia.

Then a succeeding period of global warming reversed the climatic trend; the remaining rainforests, unable to survive the rapidly changing conditions, were finally wiped out. As the climate aridified through the later Paleozoic, the rainforests were eventually replaced by seasonally-dry biomes. Though the exact speed and nature of the collapse is not clear, it thought to have occurred relatively quickly in geologic terms, only a few thousand years at most.


Major meteoroid events near the time of the CRC included the formation of the Weaubleau-Osceola structure
Weaubleau-Osceola structure
The Weaubleau-Osceola structure is thought to be a meteorite impact site in western Missouri near the towns of Osceola and Weaubleau. It is believed to have been caused by a 1200-ft meteoroid between 310 and 340 million years ago during the late Mississippian period.It is listed by the Impact...

, a serial impact which has been dated to roughly 310-340 million years ago and would have affected the Euramerican continent.

Multiple Causes

In recent years, scientists have put forth the view the idea that many of Earth's largest extinction events were due to multiple causes that coincided in time. Proponents of this view suggest multiples causes because they either don't see a single cause as sufficient in strength to cause the mass extinctions or believe that a single cause is likely to produce the taxonomic pattern of the extinction. Two of Earth's largest extinction events have been hypothesized to be multi-causal in nature:

The cause of the Permo-Triassic extinction is unclear and some authors have indicated that it may be best explained by a "Murder on the Orient Express Scenario" where multiple causes contributed to a devastating impact on life. Possible causes supported by strong evidence include the large scale volcanism at the Siberian Traps
Siberian Traps
The Siberian Traps form a large region of volcanic rock, known as a large igneous province, in the Russian region of Siberia. The massive eruptive event which formed the traps, one of the largest known volcanic events of the last 500 million years of Earth's geological history, continued for...

, the releases of noxious gases, global warming, and anoxia.

David Archibald and David E. Fastovsky discussed a scenario combining three major causes to the K-T extinction: volcanism, marine regression
Marine regression
Marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously exposed land....

, and extraterrestrial impact, together wiping out the dinosaurs 65 million years ago.

The specific cause of the CRC is not known, but certainly a multiple cause scenario is a possibility.

Fossil Sites

Many fossil sites around the world reflect the changing conditions of the Carboniferous Rainforest Collapse.
  • Hamilton, USA
  • Jarrow, UK
  • Linton, USA
  • Newsham, USA
  • Nyrany, Czechoslovakia
  • Joggins
    Joggins, Nova Scotia
    Joggins is a Canadian rural community located in western Cumberland County, Nova Scotia. On July 7, 2008 a 15 km length of the coast constituting the Joggins Fossil Cliffs was officially inscribed on the World Heritage List.- History :...

    , Canada

The Joggins Fossil Cliffs on Nova Scotia's Bay of Fundy, a UNESCO World Heritage Site is a particularly well preserved fossil site. Fossil skeletons embedded in the crumbling sea cliffs were discovered by Sir Charles Lyell in 1852. In 1859, his colleague William Dawson discovered the oldest known reptile, Hylonomus
Hylonomus was a very early reptile. It lived 312 million years ago during the Late Carboniferous period.It is the earliest unquestionable reptile ....

 lyelli and since then hundreds more skeletons have been found.

Fossil Fuels

The plant material that was lost during this extinction event was transported by water to low lying areas in bogs, marshes, lakes and inland seas. It decayed and as more material covered it, it was compressed, heated and eventually became coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

, a fossil fuels in the form of a combustible black or brownish-black rock. Coal is the largest source of energy for the generation of electricity
Electricity generation
Electricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...

 worldwide, as well as one of the largest worldwide anthropogenic sources of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 releases. Gross carbon dioxide emissions from coal usage are slightly more than those from petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

 and about double the amount from natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...


Hypothesized Future Rainforest Collapse

Tropical and temperate rainforests have been subjected to heavy logging and agricultural clearance throughout the 20th century and the area covered by rainforests around the world is shrinking. A classic pattern of fragmentation is occurring in many rainforests including those of the Amazon
Amazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...

, specifically a 'fishbone' pattern formed by the development of roads into the forest. and littoral rainforest growing along coastal areas of eastern Australia is now rare due to urban development. A number of scientific and environmental groups have hypothesized that a combination of anthropogenic climate change and deforestation may lead to future rain forest collapse.

Modern rainforest collapse may result in massive loss of biodiversity; this is of concern not only for the loss of a biome with many untapped resources but also because animal species extinction is known to correlate with habitat fragmentation. Biologists have estimated that large numbers of species are being driven to extinction (possibly more than 50,000 a year; at that rate, says E. O. Wilson of Harvard University, a quarter or more of all species on Earth could be exterminated within 50 years) due to the removal of habitat with destruction of the rainforests.

The application of palaeodata to the present conditions of this planet is still a science in its infancy, but presumably a better understanding of the process of habitat fragmentation and rainforest collapse in the past may help determine the best course of action to preserve similar ecosystems today. Specifically, examining the conditions that led to the Carboniferous Rainforest Collapse and the recovery of ecosystems after the extinction, may help contribute suitable solutions to resolving the current crisis.

Further reading