The island rule hypothesizes that species shrink or supersize to fill insular niches not available to them on the mainland.
- Brookesia nana, the nano-chameleon, may be the smallest vertebrate ever discovered.
- The "island rule" states that when new species migrate to islands, they may shrink or grow as they evolve to fill new ecological niches.
- It remains unclear whether the island rule can explain the nano-chameleon or nature's other extreme miniaturizations.
Bigger isn't always better<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTYzNTY0OS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNjM5MzYwMH0.ge-xLd6L6EXkTSUSDmAWCdoLsTsWmK0-54LILO_4pt8/img.jpg?width=1245&coordinates=0%2C279%2C0%2C280&height=700" id="1db5a" class="rm-shortcode" data-rm-shortcode-id="62958849d69721c1050aee9b45006650" data-rm-shortcode-name="rebelmouse-image" data-width="1245" data-height="700" />
The New Zealand little spotted kiwi evolved to be small to fill an ecological niche. Before the arrival of humans, its island ecosystem contained no land mammals to prey on these flightless birds.
Credit: Wikimedia Commons<p>Because of their geographic isolation, islands can have powerful effects on the evolution of their residential species. The massive Komodo dragon prowls its namesake island. The <a href="https://www.wired.com/2015/01/absurd-creature-of-the-week-barbados-threadsnake/" target="_blank" rel="noopener noreferrer">Barbados threadsnake</a> is thin enough to slither through a straw. And the fossil record recounts a history of unusually sized and bedecked creatures who established homes far from the mainland, such as <a href="https://prehistoric-fauna.com/Hoplitomeryx-matthei" target="_blank" rel="noopener noreferrer">the <em>Hoplitomeryx</em> of the Mikrotia fauna</a>.</p><p>One hypothesis for evolution's insular experimentation is "the island rule." The rule states that after establishing themselves on an island, smaller species will tend to evolve into oversized versions of their mainland ancestors. Meanwhile, larger species will tend to evolve into smaller variations. These processes are known as insular gigantism and insular dwarfism, respectively. They do this to fill the ecological niches available to them, which often differ from those they filled on the mainland.</p><p>The rule was first formulated by evolutionary biologist Leigh Van Valen and based on a <a href="https://www.nature.com/articles/202234a0" target="_blank" rel="noopener noreferrer">1964 study</a> by mammologist J. Bristol Foster—which is why it is also known as Foster's rule. Since then, many observational studies have corroborated the island rule, and there is <a href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0040334" target="_blank" rel="noopener noreferrer">even evidence</a> to suggest that new species introduced to islands will, for a time, evolve more rapidly to fill available niches.</p><p>A flock of migrant birds, for example, may find an island's lack of mammalian and reptilian predators opens the ground-living niche once forbidden to them. Such birds would then be free to grow larger, forage below the canopies, and lose the ability of flight.</p><p>This appears to be the origin story for New Zealand's flightless birds including <a href="http://nzbirdsonline.org.nz/species/south-island-giant-moa" target="_blank" rel="noopener noreferrer">the giant moa</a>, which, at six-feet tall, is the tallest bird on record. This megafauna enjoyed all the benefits of being large and in charge: fewer predators, wider ranges, access to more and varied foods, and the ability to better survive trying times. The species enjoyed island life until roughly 600 years ago, when humans arrived on the scene and <a href="https://www.sciencemag.org/news/2014/03/why-did-new-zealands-moas-go-extinct" target="_blank" rel="noopener noreferrer">hunted them to extinction</a>.</p><p>Conversely, large species may find island living restrictive as there's less room or food when compared to their mainland nurseries. Because of this, evolution may select for smaller body sizes as such bodies require less energy, and therefore fewer resources, to survive and reproduce. </p><p>This is the theory behind the miniaturization of the <a href="https://www.nps.gov/chis/learn/historyculture/pygmymammoth.htm" target="_blank" rel="noopener noreferrer">Channel Islands pygmy mammoths</a>. As the story goes, in the search for food, a herd of Columbian mammoths embarked on a journey to the super island Santaroasae. Over time, the island was cut off from the mainland. Food became scarce, and smaller mammoths had an easier time surviving and reproducing, thus passing on their Shrinky-Dink genes. Thanks to a lack of oversized predators, such evolution proved fruitful, and in less than 20,000 years, the giant Columbian mammoths evolved into a new species—the (relatively) pint-sized, 6.5-foot-tall pygmy mammoths.</p><p>To be clear, the island rule doesn't state that any species that washes ashore must go either Lilliputian or Brobdingnag. It only states that if an ecological niche becomes available and improves survival and reproductive success, then such a change is likely.</p>
Thanks to that island living?<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="c01cabce7b0b2b48a3734896c4a396db"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/SK7oHmJdDOM?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>Such constrained growth may be the cause of the Jaragua dwarf gecko's bantam evolution. The <a href="https://science.psu.edu/news/worlds-smallest-lizard-discovered-caribbean" target="_blank" rel="noopener noreferrer">gecko eats tiny insects</a> and may be filling a niche that's unavailable on the North American continent with its many, many insectivores. In fact, the island rule may explain why islands are so rich with endemic species—particularly the Caribbean, which is considered <a href="https://www.oecs.org/perb_docs/bc_part2_intro_hotspot.pdf" target="_blank" rel="noopener noreferrer">a biodiversity hotspot</a>.</p><p>Of course, scientific rules are only provisional, and scientists are prepared to revise or completely disregard a hypothesis should new evidence appear. In a field as new as biogeography, the question of whether the island rule is truly a "rule" remains an open and hotly debated question. </p><p><a href="https://onlinelibrary.wiley.com/doi/full/10.1111/jbi.13160" target="_blank" rel="noopener noreferrer">One systematic review</a> found empirical support for the island rule to be low, while <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2007.1056" target="_blank" rel="noopener noreferrer">another analysis</a> argued the rule is simply a recognition of "a few clade-specific patterns." The latter's authors conclude that "[i]nstead of a rule, size evolution on islands is likely to be governed by the biotic and abiotic characteristics of different islands, the biology of the species in question and contingency."</p><p>That brings us back to the newly discovered nano-chameleon. While it seems to follow the island rule—Madagascar being an island known for its rich biodiversity—there is a wrinkle. The species' closest relative lives right next door. <em>Brookesia karchei</em> is near twice the size of the nano-chameleon but ranges in the same mountains on mainland Madagascar. </p><p>If the nano-chameleon evolved to fill an ecological niche, why didn't those same environmental pressures miniaturize the karchei chameleon? If not the island rule, what did lead to the nano-chameleon's smaller size? As is often the case in science, further evidence may one day answer these questions.</p>
Participation in community science programs has skyrocketed during COVID-19 lockdowns.
The rapid spread of COVID-19 in 2020 disrupted field research and environmental monitoring efforts worldwide. Travel restrictions and social distancing forced scientists to cancel studies or pause their work for months.
In a joint briefing at the 101st American Meteorological Society Annual Meeting, NASA and NOAA revealed 2020's scorching climate data.
A dead heat<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTQ2MDU4Ny9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzNzM0MzIwNH0.3NrKDBoOdpFL5IXF3cDbom-Dp2RlrzJgvAciXcb0GDE/img.jpg?width=980" id="69d06" class="rm-shortcode" data-rm-shortcode-id="886a2617e756181e6a11e20a00b65dff" data-rm-shortcode-name="rebelmouse-image" data-width="1266" data-height="654" />
A graph showing the global mean temperatures from 1880–2020 (with the years 1951–1980 serving as the mean baseline).
Credit: NASA and NOAA<p>For <a href="https://data.giss.nasa.gov/gistemp/" target="_blank">its 2020 analysis</a>, NASA gathered surface temperature measurements from more than 26,000 weather stations. This data was incorporated with data from satellites as well as sea-surface temperatures taken from ship and buoy instruments. Once tallied, NASA's data showed 2020 barely edged out 2016 as the warmest year on record, with average global temperatures 1.02°C (1.84°F) above the baseline mean (1951-1980).</p><p>In a separate analysis of the raw data, NOAA found 2020 to be slightly cooler than 2016. This distinction is the result of the different methodologies used in each—for example, NOAA uses a different baseline period (1901–2000) and does not infer temperatures in polar regions lacking observations. Together, these analyses put 2020 in a statistical dead heat with the sweltering 2016 and demonstrate the global-warming trend of the past four decades.</p><p>"The last seven years have been the warmest seven years on record, typifying the ongoing and dramatic warming trend," <a href="http://email.prnewswire.com/ls/click?upn=OXp-2BEvHp8OzhyU1j9bSWuwMvMWelqIco5RbfBrouY-2BQCsSv6FnrhBjR9xReGqV57KGOs0rVc5GKMmgs-2FJKbOzjb0sJ6yjzUvrv2w75ulYk3EUck8pSjkzYhoy5ADXO0eOcn7LDjqsHyK2gp2NRf2UysMK-2F9SN4oYUmRylQcRtSUo6-2FcYeK-2B9naUetByXNCR2gF8u_FU3lc-2FvIcVOtjb4iEuBVjFYoW0IRF5dtM-2FDfzzkhmYHO5IVgq387-2BxdHEMunBZ1-2Fy0-2BJDgXnZEYvN604G1TWJfy4M4HKnIouyasgRyWEHIYmPTiDXeFrd9FqRmsl0JQfksEElkp2ITvgyFkkivWV3GiFH7z7tl1cTZ2rNh2c-2FbCRKQxkH4-2BChgYT6uWeYOvXusiC4cDsZkEBvw7lOEdPsPq78JT8F5x5gc5cMRaRJY-2FZ8q8peaKsS7Mfc5OQ6yjyEU5YUHR4QKJ1Fn-2FDuwJ5jk4Gm28sxJZNXX9IEO-2FOHlhyRcJbl6rMWcoeJZDEd-2BM8UJ5ZY-2FYqc1DHevd1Mz-2B1fQ-3D-3D" target="_blank">Gavin Schmidt</a>, director of the NASA Goddard Institute for Space Studies, <a href="https://www.sciencedaily.com/releases/2021/01/210115103020.htm" target="_blank" rel="noopener noreferrer">said in a release</a>. "Whether one year is a record or not is not really that important—the important things are long-term trends. With these trends, and as the human impact on the climate increases, we have to expect that records will continue to be broken."</p><p>And they are. According to the analyses, 2020 was the warmest year on record for Asia and Europe, the second warmest for South America, the fourth warmest for Africa and Australia, and the tenth warmest for North America. </p><p>All told, 2020 was 1.19°C (2.14°F) above averages from the late-19<sup>th</sup> century, a period that provides a rough approximate for pre-industrial conditions. This temperature is closing in on the Paris Climate Agreement's preferred goal of <a href="https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreemen" target="_blank" rel="noopener noreferrer">limiting global warming to 1.5°C</a> of those pre-industrial conditions.</p>
2020's hotspot was—the Arctic?<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTQ2MDU5My9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyMTA5OTU1MH0.0ZCixGwhHbjmyO6By_eaMI-cXrM2-rsPq32J-pAVWPs/img.jpg?width=980" id="34c94" class="rm-shortcode" data-rm-shortcode-id="846b12bfa65c6d1b8d0a5b0d0214e091" data-rm-shortcode-name="rebelmouse-image" data-width="1106" data-height="672" />
A map of global mean temperatures in 2020 shows an scorching year for the Arctic.
(Photo: NASA and NOAA)<p>Heatwaves have become more common all over the world, but a region that really endured the heat in 2020 was the <a href="https://nsidc.org/cryosphere/arctic-meteorology/climate_change.html#:~:text=Over%20the%20past%2030%20years,climate%20change%20in%20the%20Arctic." target="_blank">Arctic</a>.</p><p>"The big story this year is Siberia; it was a hotspot," Russell Vose, chief of the analysis and synthesis branch of NOAA's National Centers for Environmental Information, said during the briefing. "In May, some places were 18°F above the average. There was a town in Siberia […] that reported a high temperature of 104°F. If that gets verified by the World Metrological Organization, it will the first there's been a weather station in the Arctic with a temperature above 100°F."</p><p>The Arctic is warming at three times the global mean, thanks to <a href="https://nsidc.org/cryosphere/arctic-meteorology/climate_change.html#:~:text=Over%20the%20past%2030%20years,climate%20change%20in%20the%20Arctic." target="_blank">a phenomenon known as Arctic Amplification</a>. As the Arctic warms, it loses its sea ice, and this creates a feedback loop. The more Arctic sea ice loss, the more heat introduced into the oceans; the more heat introduced, the more sea ice loss. And the longer this trend continues, the more devastating the effects.</p><p>For example, since the 1980s, there's been a 50 percent decline in sea ice, and this loss has exposed more of the ocean to the sun's rays. That energy then gets trapped in the ocean as heat. As the <a href="https://www.climate.gov/news-features/understanding-climate/climate-change-ocean-heat-content" target="_blank" rel="noopener noreferrer">ocean heat content</a> rises, it threatens rising sea levels and the sustainability of natural ecosystems. In 2020 alone, 255 zeta joules of heat above the baseline were introduced into Earth's oceans. In (admittedly) dramatic terms, that's <a href="https://www.mprnews.org/story/2020/01/14/twin-cities-scientist-heat-of-5-to-6-hiroshima-atom-bombs-per-second-into-earths-oceans" target="_blank" rel="noopener noreferrer">the equivalent of introducing 5 to 6 Hiroshima atom bombs</a> worth of energy every second of every day.</p><p>Looking beyond the Arctic, the average snow cover for the Northern Hemisphere was also the lowest on record. Like the Arctic sea ices, such <a href="https://nsidc.org/cryosphere/snow/climate.html#:~:text=Snow's%20effect%20on%20climate,especially%20the%20western%20United%20States." target="_blank" rel="noopener noreferrer">snow cover</a> helps regulate Earth's surface temperatures. Its melt off in the spring and summer also provides the freshwater ecosystems rely on to survive and farmers need to grow crops, especially in <a href="https://bigthink.com/surprising-science/too-many-trees?rebelltitem=2#rebelltitem2" target="_self">the Western United States</a>.</p>
Natural disasters get a man-made bump<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTQ2MDU5NS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2MjUwMjE0Mn0.R_juvxCWUw-S9RDkAobjXeMn2qMHg-XVgsOHW74Uz-s/img.jpg?width=980" id="51830" class="rm-shortcode" data-rm-shortcode-id="7b3e734e1d03eaec341dca40df0939f0" data-rm-shortcode-name="rebelmouse-image" data-width="1123" data-height="672" />
A map of 2020's billion-dollar weather and climate disasters, which totaled approximately $95 billion in losses.
Credit: NASA and NOAA<p>2020 was also a record-breaking year for natural disasters. In the U.S. alone, there were 22 billion-dollar disasters, the most ever recorded. Combined, they resulted in a total of $95 billion in losses. The western wildfires alone consumed more than 10 million acres and destroyed large portions of Oregon, Colorado, and California.</p><p>The year also witnessed a record-setting Atlantic Hurricane season with more than 30 named storms, 13 of which were hurricanes. Typically, the World Meteorological Organization <a href="https://www.nhc.noaa.gov/aboutnames_history.shtml#:~:text=Instead%20a%20strict%20procedure%20has,is%20repeated%20every%20sixth%20year." target="_blank">names storms</a> from an annual list of 21 selected names—one for each letter of the alphabet, minus Q, U, X, Y, and Z. For only <a href="https://www.npr.org/2020/09/18/914453403/so-2020-new-storm-forms-named-alpha-because-weve-run-out-of-letters" target="_blank" rel="noopener noreferrer">the second time in history</a>, the Organization had to resort to naming storms after Greek letters because they ran out of alphabet.</p>
For the record, there's a consensus about the record<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="9bb94f5d5a58d40f03e1515f3c2e467c"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/gzksqQDI_kE?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>Such records are a dramatic reminder of climate change's ongoing effect on our planet. They make for an eye-catching headline, sure. But those headlines can sometimes mask the fact that these years are part of decade-long trends, trends providing a preview of what a climate-changed world will be like. </p><p>And in case there was any question as to whether these trends were the result of natural processes or man-made conditions, Schmidt and Vose did not mince words. </p><p>As Schmidt said in the briefing: "Many, many things have caused the climate to change in the past: asteroids, wobbles in the Earth's orbit, moving continents. But when we look at the 20<sup>th</sup> century, we can see very clearly what has been happening. We know the continents have not moved very much, we know the orbit has not changed very much, we know when there were volcanoes, we know what the sun is doing, and we know what we've been doing."</p><p>He continued, "When we do an attribution by driver of climate change over the 20<sup>th</sup> century, what we find is that the overwhelming cause of the warming is the increase of greenhouse gases. When you add in all of the things humans have done, all of the trends over this period are attributable to human activity."</p><p>The data are in; the consensus is in. The only thing left is to figure out how to prevent the worst of climate change before it's too late. As bad as 2020 was, it was only a preview of what could come.<strong></strong></p>
Across the world, wildlife is under severe threat.
Earth's fate and the devastation of the natural world were recently put under the microscope with the release of Sir David Attenborough's Netflix documentary A Life On Our Planet.
Carbon locked in soils can be emitted by bacteria. Turning up the heat on them releases more carbon.
- A new study shows that an increase in temperature can increase the amount of carbon released by the soil.
- This is in line with previous studies, though this one demonstrates a larger increase than the older experiments.
- The risk is that increasing temperatures cause a positive feedback loop.