Tree

[[File:Royal Oak, Boscobel.jpg|thumb|right|165px|The Royal Oak of England]]
{{biology}}
A '''tree''' is a large [[plant]] with a woody stem. There is no clear definition of what constitutes a tree, and they do not form a distinctive biological group or [[clade]], as {{wpl|angiosperm}} trees like maples are more closely related to grass than {{wpl|gynmosperm}} trees like pines,<ref>[https://www.mountgrace.org/about/news/post/forest-stewardship-gymnosperms-vs-angiosperms Forest Stewardship: Gymnosperms vs Angiosperms], ''Mount Grace Land Conservation Trust'' 5 December 2022</ref> and there are other trees like {{wpl|tree fern|tree ferns}} that aren't closely related to either group. They are generally considered a good thing: they produce [[oxygen]], they can combat [[global warming]] by absorbing atmospheric carbon dioxide and storing carbon, they produce lots of useful [[food]]stuffs, they provide shelter and home to many [[animal]]s and other plants, and they look nice.

==Types of trees==
Trees are a great example of [[convergent evolution]], as many different plant lineages have evolved into trees as it's a great way of being able to grow taller than other plants to get more sunlight. Some of the major types of trees include:

===Lepidodendrales===
[[File:Lepidophloios.JPG|thumb|right|165px|A fossil of ''{{wpl|Lepidophloios||'',}} a scale tree.]]
{{wpl|Lepidodendrales||,}} also known as "scale trees", are a group of {{wpl|lycophyte|lycophytes|,}} a group of plants that was once very diverse but now are largely limited to {{wpl|club mosses||.}} Being some of the earlier vascular plants, having diverged from the lineage in the Silurian, these trees reproduced using spores instead of seeds. While the scale trees are long [[extinct]], they left a lasting impact, being the main plants that are responsible for the massive [[coal]] swamps.<ref>[https://samnoblemuseum.ou.edu/common-fossils-of-oklahoma/plant-fossils/fossils-by-plant-group/fossil-lycophytes/ Fossil Lycophytes], ''Sam Noble Museum''</ref>

===Ferns===
While today are mainly associated with the smaller plants of their clade, ferns have actually evolved into trees no less than three times, with the most recent lineage (appearing in the late Jurassic), tree ferns, still being alive today. Originally native to [[Australia]] and [[New Zealand]], tree ferns were introduced to other places as a result of human activity, and like their smaller cousins tree ferns have fronds and reproduce using spores.<ref>[https://animals.sandiegozoo.org/plants/tree-fern Tree Fern], ''San Diego Zoo''</ref> The extinct lineages include ''{{wpl|Tempskya}}'' as well as some extinct members of the still extant ''{{wpl|Osmundaceae||''.}}

===Seed ferns===
Despite their name, these were not closely related to modern ferns. Although they looked superficially similar, these plants produced seeds instead of spores, and they were likely the first lineage to do so. While they were also contributors to the coal swamps, they sadly went extinct in the [[K-Pg extinction event]].<ref>[https://www.nps.gov/articles/seed-fern.htm Seed Fern Fossil], ''National Park Service''</ref>

===Gymnosperms===
====Ginkgos====
''{{wpl|Ginkgo biloba}}'' is a [[living fossil]], being the last remaining descendant of an order that first showed up in the Permian. In fact, they barely avoided extinction during the [[ice age]], with cultivation by [[China|Chinese]] monks being the main reason they survive today, and since then they've been cultivated across the planet.<ref>[https://ucmp.berkeley.edu/seedplants/ginkgoales/ginkgofr.html Ginkgoales: Fossil Record], ''University of California Museum of Paleontology''</ref> The ginkgo is famous for its smelly seeds that are used in [[Traditional Chinese Medicine]], although Western woo-meisters seem to prefer the leaves (probably due to the aforementioned smell). As it thrives quite well in urban environments, it's one of the plant species that humans have actually significantly aided the survival of.<ref>[https://e360.yale.edu/features/peter_crane_history_of_ginkgo_earths_oldest_tree The Life Story of The Oldest Tree on Earth], Roger Cohn, ''Yale School of the Environment'' 1 May 2013</ref>

====Conifers====
Conifers are so named because they bear cones that contain their seeds. Most conifers have needles or scale-like leaves, and most of them don't shed their leaves during the winter ({{wpl|larch|larches}} being the exception). Conifers are most known for dominating the vast {{wpl|taiga}} of [[North America]], [[Europe]], and [[Asia]],<ref group=note>Which is actually a new environment, geologically speaking: the taiga's existence is a direct result of the most recent glacial maximum of the ice age</ref> although they can really survive in many different environments, including arid and tropical ones. The tallest ({{wpl|coast redwood||),}} oldest ({{wpl|bristlecone pine||),}} and largest by volume ({{wpl|giant sequoia||)}} of all extant trees are all conifers.<ref>[https://www.usgs.gov/news/featured-story/oh-christmas-tree-science-conifer-trees Oh Christmas Tree: The Science of Conifer Trees], ''US Geological Survey''</ref>

===Angiosperms===
Angiosperms are currently the dominant group of plants, having split from the gymnosperms 300 million years ago but only truly diversifying during the Cretaceous. They are distinct from other plants because they bear flowers, and by extension, fruit.<ref group=note>Note that the botanical definition of a "fruit" (which includes things like acorns and star anise, not to mention tomatoes) is quite a bit wider than the culinary one.</ref> Angiosperm trees are often referred to as deciduous, meaning they lose their leaves in winter, but keep in mind larches are technically deciduous despite being conifers and most tropical angiosperm trees don't lose their leaves over winter.<ref group=note>The opposite of "deciduous" isn't "coniferous" as many believe, but rather "evergreen".</ref><ref>[https://www.worldatlas.com/articles/what-are-the-differences-between-evergreen-and-deciduous-trees.html What Are The Differences Between Evergreen And Deciduous Trees?], ''World Atlas''</ref>

==How many==
It isn't clear how many trees there are on [[Earth]], but a 2015 estimate reported in ''Nature'' was 3 trillion of the things, which is a lot more than there are people.<ref>[https://www.bbc.co.uk/news/science-environment-34134366 Earth's trees number 'three trillion'], BBC, 3 September 2015</ref>

==Tree-planting and global warming==
Tree-planting is often seen as a good way of combatting global warming by absorbing large amounts of carbon.<ref name=guardian20190704>[https://www.theguardian.com/environment/2019/jul/04/planting-billions-trees-best-tackle-climate-crisis-scientists-canopy-emissions Tree planting 'has mind-blowing potential' to tackle climate crisis], The Guardian, 4 July 2019</ref><ref name=discover>[https://www.discovermagazine.com/planet-earth/we-cant-just-plant-billions-of-trees-to-stop-climate-change We Can’t Just Plant Billions of Trees to Stop Climate Change], Discover Magazine, 10 July 2019</ref> One problem is that if, as mentioned, there are 3 trillion trees already, then making a significant difference will require planting a lot. Research led by Tom Crowther at ETH Zurich published in ''Science'' in 2019 recommended planting one trillion trees on 11% of the Earth's land to eventually absorb 200 gigatonnes of carbon from the atmosphere, around two-thirds of the total anthropogenic carbon in the atmosphere.<ref name=guardian20190704/>

There are also risks in that you can't just stick trees anywhere. They require water and other resources, and may have effects on local ecosystems, particularly with low-quality schemes that just plant lots of one or two types of tree rather than seeking to preserve or restore existing types of forest.<ref name=discover/> One traditional method of reforestation is known as "pines in lines", in which pine trees are planted in rows, but this requires expensive maintenance by foresters meaning it may be prohibitively expensive.<ref>[https://www.nationalgeographic.com/environment/2019/04/how-to-regrow-forest-right-way-minimize-fire-water-use/ Tree-planting programs can do more harm than good], National Geographic, 26 April 2019</ref> It's also important to preserve farmland for growing crops if we want to stop people dying of hunger.

A number of ambitious schemes have been announced. [[Ethiopia]] planned to plant 4 billion trees by October 2019, including 350 million on just one day, although it is unclear how many they actually planted.<ref>[https://www.bbc.co.uk/news/world-africa-49266983 Deforestation: Did Ethiopia plant 350 million trees in a day?], BBC Reality Check, 11 Aug 2019</ref> In 2017 [[Pakistan]] completed a goal of planting 1 billion trees (despite allegations of corruption).<ref>[https://www.weforum.org/agenda/2018/07/pakistan-s-billion-tree-tsunami-is-astonishing/ Pakistan has planted over a billion trees], World Economic Forum, 02 Jul 2018</ref> Pakistan's scheme was inspired by the International Union for Conservation of Nature's (IUCN) Bonn Challenge launched in 2011, which aimed to restore 150 million hectares of forest globally by 2020 and 350 million hectares by 2030.<ref>[https://www.bonnchallenge.org/about-the-goal#commitments About the Bonn Challenge Goal], Bonn Challenge website</ref> A [[Turkey|Turkish]] scheme for National Forestation Day on 11 November 2019 is alleged to have ended in failure with 90% of the 11 million trees dead within a few months.<ref>[https://www.theguardian.com/world/2020/jan/30/most-of-11m-trees-planted-in-turkish-project-may-be-dead Most of 11m trees planted in Turkish project 'may be dead'], The Guardian, Jan 30, 2020</ref>

Before the [[UK]]'s 2019 general election, the [[British Labour Party]] announced plans to plant 2 billion trees; this is a bit more than the recommendations of the UK government Committee on Climate Change which recommended 1.5 billion trees be planted by 2050 and appears very ambitious but not impossible.<ref>[https://www.theguardian.com/politics/2019/nov/28/is-labours-plan-to-plant-2-billion-trees-realistic Is Labour's plan to plant 2bn trees realistic?], The Guardian, 28 Nov 2019</ref><ref name=gramling/> Labour lost the election, and we'll have to wait a while to see if 1.5 billion trees are planted. 

Growing trees isn't as simple as dropping a seed in the ground. Most schemes, such as those in Pakistan and Ethiopia, rely on tree nurseries to produce seedlings which must then be planted in the correct location. Growing trees require protection from grazing animals, as well as the risk of disease and insect pests, and can suffer from a lack of water and nutrients.<ref>[https://www.bigblogofgardening.com/what-are-the-most-common-threats-to-trees-in-your-landscape/ What Are the Most Common Threats To Trees in Your Landscape?], Big Blog of Gardening, Sep 2018</ref> So they may require water, fertilizer, pesticide, and the infrastructure (roads/tracks, accommodation for foresters, etc) to plant and maintain them. All this adds to the costs and can provide a negative environmental impact, but it's the sort of thing farmers and foresters have been doing for millennia.

Frequently, when governments get behind the idea of tree planting on a massive scale, it winds up being tree plantations, which have a relatively relatively minor impact compared to restoring land to natural forest (3 vs. 42 gigatons of sequestered carbon).<ref name=gramling>[https://www.sciencenews.org/article/planting-trees-climate-change-carbon-capture-deforestation Why planting tons of trees isn’t enough to solve climate change: Massive projects need much more planning and follow-through to succeed – and other tree protections need to happen too] by Carolyn Gramling (July 9, 2021 at 6:00 am) ''Science News''.</ref> Restoring natural forests is also a much more difficult task than making plantations because it usually requires specific plans tailored to each location so that that there is buy-in from the communities who will be responsible for protecting the forests.<ref name=gramling/> There is likewise an important need to protect natural forests that are still intact because there is constant economic pressure for deforestation, and this too requires tailoring solutions to local communities.<ref>[https://www.sciencenews.org/article/planting-trees-protect-forests-climate-change The first step in using trees to slow climate change: Protect the trees we have: By holding onto the big, old trees, more carbon will stay sequestered] by Susan Milius (July 13, 2021 at 6:00 am) ''Science News''.</ref> Adding trees within croplands can both increase carbon sequestration and reduce pressure on deforestation with often the added benefit of increased food yield.<ref>[https://www.sciencenews.org/article/trees-crops-agroforestry-climate-biodiversity Mixing trees and crops can help both farmers and the climate: Agriculture that includes trees boosts food production, stores carbon and saves species.] by Jonathan Lambert (July 14, 2021 at 6:00 am) ''Science News''.</ref>

==Woo and legend==
===Trees cause pollution===
[[File:Sequoiadendron giganteum at Kenilworth Castle.jpg|thumb|right|165px|Quick, someone stop this dastardly producer of pollution!]]
The idea that trees cause pollution is a [[Fractal wrongness|gloriously stupid concept]] foisted upon the public in 1981 by [[President of the United States|U.S. President]] [[Ronald Reagan]].  The full quote of his statement was: {{blockquote|Trees cause more [[pollution]] than [[automobile]]s do.<ref>http://www.theguardian.com/science/2004/may/13/thisweekssciencequestions3</ref>}}
Reagan was falsely referencing the photochemical reaction that causes ground-level [[ozone]] pollution (GLOP), also known as photochemical smog.<ref>http://www.epa.gov/oar/oaqps/gooduphigh/bad.html#6</ref> Smog is created when automobile and power plant emissions are broken down into ozone and other chemicals by strong UV radiation. These reactions are then further amplified by the presence of various volatile organic compounds (VOCs).<ref>{{see-wp|Photochemical smog}}</ref> During hot and sunny weather, many tree species release volatile organic compounds into the atmosphere, notably {{wpl|terpenes||}} and isoprenes (pine pitch is a terpene). Other VOCs that contribute to GLOP include gasoline, kerosene, paint, paint thinner and other industrial solvents.
====The truth====
Reagan's statement was disingenuous because volatile organic compounds produced by trees do not cause pollution any more than the [[Sun]] itself causes pollution. Reagan might as well have said, "The Sun causes more pollution than automobiles do." Photochemical ozone pollution is created when automobile and power plant pollution is broken down by strong sunlight ''in the presence'' of any number of volatile organic compounds.

GLOP or photochemical smog is only created in areas that receive large amounts of pollution from automobiles and power plants.<ref>http://www.shodor.org/master/environmental/air/photochem/smogapplication.html</ref> Trees are not required to create it. Without the input of large amounts of synthetic nitrogen oxides by cars and power plants, the VOCs released by forests on a summer day have nothing to react with, and thus do not create ''any'' pollution. On the contrary, photochemical smog is actually very ''harmful'' to trees— reducing their growth, making their shed leaves decay slower and affecting symbiotic insects and other small organisms that live on them.<ref> [https://news.wisc.edu/study-shows-how-pollution-affects-tree-growth/ Study shows how pollution affects tree growth.] ''University of Wisconsin.''</ref>

===Carnivorous trees===
This apparently goes back to a disreputable [[journalist]] named Edmund Spencer who in 1874 wrote a report about natives of Madagascar sacrificing somebody to a carnivorous tree. Untrue.<ref>{{wpa|Man-eating tree}}</ref>

===Tree of the knowledge of good and evil and Tree of life===
These appear in {{bible|Genesis|2|3}}. [[Adam and Eve]] ate the fruit of the tree of knowledge, and as a result were thrown out of the [[Garden of Eden]]. There is a lot of speculation about what kind of trees they were. While commonly believed to be an [[apple]], there is no evidence in the [[Bible]] for this, and it's likely out of place anyway as apples originated in [[Kazakhstan]] and not the [[Middle East]].<ref>[https://www.livescience.com/what-was-forbidden-fruit-in-eden.html Was the 'forbidden fruit' in the Garden of Eden really an apple?], Ashley P. Taylor, ''Live Science'' 27 March 2021</ref>

==See also==
Tree topics:
* [[Dendrochronology]] — calculating dates using tree rings
* [[Petrified forest]] — stone trees
* [[Tree of life]] — various meanings
* [[Superfoods]] — including apple, cacao, walnut, and possibly other trees
* [[American tall tales]] — including Johnny Appleseed who planted trees and Paul Bunyan who chopped them down again
* [[Ancient giant silicon-based tree hypothesis]] — your guess is as good as mine

Specific types of tree and their products:
* [[Açaí berry]]
* [[Apple cider vinegar]]
* [[Christmas#The Christmas tree|Christmas tree]] — usually pines
* [[Coffee]] is a small tree — some varieties grow well in shade as an understory crop
* [[Graviola]]
* [[Palm oil]]
* [[Tar water]] — an aromatic pine tree product
* [[Yew]]

Famous people whose lives involved trees in popular mythology:
* [[Adam and Eve]]
* [[Isaac Newton]] 
* [[George Washington]]<ref>[https://www.mountvernon.org/library/digitalhistory/digital-encyclopedia/article/cherry-tree-myth/ Cherry Tree Myth] ''Mount Vernon Ladies’ Association''.</ref>

==Notes==
{{reflist|group=note}}

==References==
{{reflist|2|80%}}

[[Category:Environmentalism]]
[[Category:Evolution]]
[[Category:Global warming]]
[[Category:Paleontology]]
[[Category:Plants]]

Categories: Environmentalism, Evolution, Global warming, Paleontology, Plants