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= No-analog Communities = No-analog (variants may omit the hyphen and/or use the British English analogue), or alternately novel climates, climatic conditions ("no-analog climates") or biological communities ("no-analog communities") in paleoecology and ecological forecasting are ecological communities that do not have a comparable modern comparison i.e. ecosystems that are novel compared to the modern day. Novelty is defined by the degree to which an ecosystem is unlike any others based on a variety of factors. No-analog communities can generally be described at the ecosystem level, and may consist of and may consist of extant species that coexist in assemblages not seen today. This becomes a problem in paleoecology due to the concept of uniformitarianism, or using the present to analyse the past, with this comes the caveat that the more distant the past becomes, the less the present is representative. . All of these factors combine to create ecological systems that we can not adequately make predictions about. Our current knowledge of no-analog communities is in paleo records and communities with invasive species, however in the future, no-analog communities are projected to arise again given the trajectory of climate change.

Drivers & Theories
A large potential driver in the creation of no-analog communities is environmental change. By definition if any environmental or other changes result in a new and previously unobserved ecosystem that that would be a new no-analog community. In the late Pleistocene, advancing ice sheets in North America caused a mass migration of northern species into the current day United States. Here we see a large intermingling of both plant and animal species that resulted in a new ecosystem previously unobserved in the fossil record and not found since the end of the last ice age. Novelty can arise for a variety of reasons, in biotic or abiotic ways. Abiotic changes, such as alterations to atmospheric conditions, or soil nutrient loads result in the biotic changes that we see in paleo-records. During times of climate change (such as the last ice age and other events driven by the milankovitch cycle) environmental conditions change in abiotic was, and this allows for the creation of new niches, and destruction of others. When the potential niches of a region change, species begin to migrate independently of the other ones that they used to exist with and fill these niches in new ways. Thus new groupings of biota are found together that would never have previously coexisted.

Modeling
In the study of no-annalog communities there is often a focus on the tropic and subtropical range because as the earth warms, the warmest areas are the first to see species begin to extend their range.

Challenges
In modeling, it is difficult to accurately represent the potential for future communities because species never fill the full extent of their potential niche due to other biotic limitations. Additionally, species can begin to develop unknown niches during periods of change.

Late Quaternary
During the late glacial period, plant communities in the United States contained a wider variety of taxa than they do today over a much larger region. High pollen abundances of Ash, Hophornbeams/Hornbeans and Elms (Fraxinus + Ostrya/Carpinus+Ulmus) found in Alaska and the Eastern United States date back to 21,000 years BP to 12,000 years BP. These communities are considered novel since these areas are currently dominated by Picea, Pinus, Quercus, and Cyperacaea.

For example, the density and diversity of the mosaic of North American mammal species has been compared to the mammalian diversity of the African Serengeti today. This is due to the large variation of megafauna that roamed much of North America including herbivores such as the woolly mammoth as well as apex predators like the dire wolf and saber tooth cat. This community however saw a large drop in diversity towards the beginning of the Holocene, which was accompanied by a large increase of global temperature. This resulted in a large decrease in both floral and faunal diversity, including the extinction of many of North America’s megafauna. Every mammal species over 1000 kilograms went extinct and 50% of species between the weights of 1000 kg and 32 kg went extinct.

Mesozoic Era
Mid Jurassic-Cretaceous floral assemblages of ferns and Ginkgo biloba can be classified as a no-analog/novel community since many of the species are still extant yet fail to represent any modern communities. Ginkgo species, along with extant and extinct species of cycads, ferns and shrubs were widely distributed throughout the Northern hemisphere. The survival of Ginkgo’s last remaining species, Ginkgo biloba, can be attributed to glacial refugia located within South-Western China.

Future No-Analog/Novel Communities
Another example of a no-analog/novel community is the appearance of non-native vegetation in early successional forests of Puerto Rico. Prior to the abandonment of farmlands in the late 1940s to 1950s, 75% of the land had been deforested. The abandonment of farmlands encouraged the growth of non-native vegetation in early successional forests, leading to an increase of 50-57% in the islands forest cover. These early successional species provided habitats for native birds, which dispersed the seeds of native vegetation throughout the island. Now the island has a unique mixture of non-native and native vegetation that have begun to restore ecosystem functions of the island

In the future
According to recent models, no-analog communities are projected to appear by the end for the 21st century (by 2100). These models produce a high likelihood of no analogs appearing in the Amazon, Southeastern US, The African Sahara and Sehal, Arabian Peninsula, India, China, and Northern Australia. There is also the possibility for novel climates to arise in the Western US, Central Asia, and Argentina. The region that shows the least risk of no-analog communities arising by the end of the 21st century are the northern most parts of the globe. As the climate has begun to shift, species that have good disposal methods have already been observed shifting their home ranges at accelerated rates. However, not all species are as efficient in dispersal and adaptation. Thus community change happens due to varying rates. This is a point of contention in ecological modeling right now given that we are moving toward future no analog communities.

Extinctions are caused when niches are eliminated from a habitat and the species in question does not a broad enough niche or fast enough dispersal method to follow its niche. Additional problems are encountered when a species optimum temperature ranges are no longer present in its given region and it does not migrate from that region in due time. Often the driver of species extinction is the result of poor dispersal mechanisms during times of climate change given the inability to follow their range.

With Matt and Matt $$(Matt^2?)$$
No-analog Communities <- preferred

This article has 1 sentence and a few examples. For this article we would build out the whole article. Including overview, history of theory, strategies to overcome the issue, examples, prevalence through time periods/causes. Even if we couldn't add all of this, we would be able to add some much needed bulk to the article.

Quaternary extinction event

This article is about the Quaternary extinctions and and the multiple theories surrounding them. It is pretty biased towards the human caused extinctions theory and does not represent the climate change hypothesis very thoroughly. Given we’ve spent a moderate amount of time discussing this and have a number of relevant sources we could potentially improve these sections a lot. Other sections of the article need citing and areas that are back by opinion exist that need to be changed.

Late Pleistocene

This article is incredibly sparse, with and introduction and a brief discussion of bison in North America. The talk page also includes some discussion over terminology inaccuracies within the article. Firstly we would review the article for accuracy, and round out the citations. Then adding sections about characteristic flora and fauna, climate, extinction events, and transition to holocene.

Riverbluff Cave

This page describes Riverbluff cave, a site where multiple pleistocene fossils have been discovered. It has many dead references and gives a vague description of the species found in the cave. To fix it we would include functional citations, and a detailed list of species found in the the citations.

Oxygen-16

This is a stub article that defines oxygen-16 and the processes through which it is formed. It mentions nothing about its applications in palaeoecology while oxygen-18 mentions palaeoecology in great detail. We would draw a lot of information from the oxygen-18 page’s citations since oxygen-18 and oxygen-16 are two sides of the same coin and add paleoecology section to the article.

Article evaluation: Holocene
The introduction doesn't seem to have a clear idea of where it is going but rather a bunch of disjointed facts that may or may not be relevant to basic background, with very few citations to back the information there

Most of the article is almost entirely missing citations

There seam to be a variety of different organizations and researchers referenced, but without citation

The article is rated as a "start" class, so it has been identified as needing a lot of work

The talk page contains a variety of different problems from issues of scientific accuracy in naming the holocene and epoch vs era, to issues of tense and grammar in the article.