Tag: climate change | Page 3

11.2.17

When whale I sea you again?

Image of a humpback whale tail from the Palmer Station LTER. Photo credit Beth Simmons.

The activities are as follows:

People have hunted whales for over 5,000 years for their meat, oil, and blubber. In the 19^th and 20^th centuries, pressures on whales got even more intense as technology improved and the demand for whale products increased. This commercial whaling used to be very common in several countries, including the United States. Humpback whales were easy to hunt because they swim slowly, spend time in bays near the shore, and float when killed. Before commercial whaling, humpback whales were one of the most visible animals in the ocean, but by the end of the 20^th century whaling had killed more than 200,000 individuals.

Today, as populations are struggling to recover from whaling, humpback whales are faced with additional challenges due to climate change. Their main food source is krill, which are small crustaceans that live under sea ice. As sea ice disappears, the number of krill is getting lower and lower. Humpback whale population recovery may be limited because their main food source is threatened by ongoing ocean warming.

One geographic area that was over-exploited during times of high whaling was the South Shetland Islands along the Western Antarctic Peninsula (WAP). The WAP is in the southern hemisphere in Antarctica. Humpback whales migrate every year from the equator towards the south pole. In summer they travel 25,000 km (16,000 miles) south to WAP’s nutrient-rich polar waters to feed, before traveling back to the equator in the winter to breed or give birth. Today the WAP is experiencing one of the fastest rates of regional climate change with an increase in average temperatures of 6^° C (10.8^° F) since 1950. Loss of sea ice has been documented in recent years, along with reduced numbers of krill along the WAP.

Logan is a scientist who is studying how humpback whales are recovering after commercial whaling. Logan’s work helps keep track of the number of whales that visit the WAP in the summer. He also determines the sex ratio, or ratio of males to females, which is important for reproduction. The more females in a population compared to males, the greater the potential for having more baby whales born into the next generation. Logan predicts there may be a general trend of more females than males along the WAP as the season progresses from summer to fall. Logan thinks that female humpback whales stay longer in the WAP because they need to feed more than males in order to have extra nutrients and energy before they birth their babies later in the year. This extra energy will be needed for their milk supply to feed their babies.

The Palmer LTER station when Logan and others scientists live while they conduct research on whales.

Humpback whales only surface for air for a short period of time, making it difficult to determine their sex. In order to identify surfacing whales as female or male, scientists need to collect a biopsy, or a sample of living tissue, in order to examine the whale’s DNA. Logan worked with a team of scientists at Oregon State University and Duke University to engineer a modified crossbow that could be used to collect samples. Logan uses this crossbow to collect a biopsy sample each time they spot a whale. To collect a sample, Logan aims the crossbow at the whale’s back, taking care to avoid the dorsal fin, head, and fluke (tail). He mounts each arrow with a 40mm surgical stainless steel tip and a flotation device so the samples will bounce off the whale and float for collection. The samples are then frozen so they can be stored and brought back to the lab for analysis. Logan also takes pictures of each whale’s fluke because each has a pattern unique to that individual, just like the human fingerprint. Additionally, at the time of biopsy, Logan records the pod size (number of whales in the area) and GPS location.

Logan’s data are added to the long-term datasets collected at the WAP. To address his question he used data from 2010-2016 along the WAP and other feeding grounds. Logan’s data ranges from January to April because those are the months he is able to spend at the research station in the WAP before it gets too cold. Logan has added to the scientific knowledge we have about whales by building off of and using data collected by other scientists.

Featured scientist: Logan J. Pallin from Oregon State University. Written by: Alexis Custer

Flesch–Kincaid Reading Grade Level = 10.7

Additional teacher resources related to this Data Nugget:

To see more images of humpback whales, and the Palmer Research Station in the WAP where Logan works, check out this PowerPoint. This can be shared with students in class after they read the Research Background and before they move on to the data.
More data from this region can be found on the DataZoo, Palmer LTER’s online data portal. To access data on this portal, follow instructions found on this “cheat sheet”. For files that have been compiled for educators, check out this Google Drive folder.
For his research, Logan has traveled to United States Antarctic Programs’ Palmer Research Station on the WAP during the austral summer and fall and will be departing again for the WAP in January 2018. He is part of a team of scientists interested in Palmer Long Term Ecological Research, which is funded through the National Science Foundation, documenting changes on in the Antarctic ecosystem.
For more information on whale research at Palmer Station LTER and the WAP, check out this website.
For additional classroom activities dealing with Palmer Station LTER data, check out this website.
The International Whaling Commission (IWC) was created in
1946 in Washington D.C. in hopes to provide conservation to whale stocks around the world. In 1982, the IWC placed a moratorium on commercial whaling. Fore more information on the IWC and humpback whales, check out their website.

About Logan: Logan is interested in determining how humpback whales are recovering after commercial whaling. Logan first got interested in working with marine mammals when he was an undergraduate student at Duke University and had the opportunity to work as a field technician on a project with some scientists at Duke. He quickly realized this was what he wanted to do and that studying humpbac whales was particularly interesting as they appear to have all rebounded quite heavily in the Southern Hemisphere. Assessing why this recovery was happening so fast and why now, was something Logan really wanted to look at. After graduating from college, he continued to work with marine mammologists as a graduate student to receive his Masters in Science from Oregon State University. In the fall of 2017, he started his work on a PhD from University of California, Santa Cruz continuing asking questions and learning more about whales around Antarctica.
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11.17.16

When a species can’t stand the heat

An adult male tuatara. Photo by Scott Jarvie.

The activities are as follows:

Tuatara are a unique species of reptile found only in New Zealand. Tuatara look like lizards but they are actually in their own reptile group. Tuatara are the only species remaining on the planet from this lineage, one that dates to the time of the dinosaurs! Tuatara are similar to tortoises in that they are extremely long-lived and can sometimes live over 100 years. Tuatara start reproducing when they are about 15–20 years old and they breed infrequently.

North Brother Island, one of the small New Zealand islands where tuatara are still found today. Photo by Jo Monks.

The sex of tuatara is not determined by sex chromosomes (X or Y) as in humans. Instead, the temperature of the nest during egg development is the only factor that determines the sex of tuatara embryos. If the egg develops with a low temperature in the nest it will be female, but if it develops with a high temperature it will be male. This process happens in many other species, too, including some turtles, crocodiles, lizards, and fish. However, most species are the opposite of tuatara and produce females at the warmest temperatures.

Today, tuatara face many challenges. Humans introduced new predators to the large North and South Islands of New Zealand. Tuatara used to live on these main islands, but predators drove the island populations to extinction. Today, the tuatara survive only on smaller offshore islands where they can escape predation. Because many of these islands are small, tuatara can have low population numbers that are very vulnerable to a variety of risk factors. One of the current challenges faced by these populations is climate change. Similar to the rest of the world, New Zealand is experiencing higher and higher temperatures as a result of climate change, and the warm temperatures may impact tuatara reproduction.

Kristine collecting data on a tuatara in the field. Photo by Sue Keall.

North Brother Island has a small population of tuatara (350–500 individuals) that has been studied for decades. Every single tuatara has been marked with a microchip (like the ones used on pet dogs and cats), which allows scientists to identify and measure the same individuals repeatedly across several years. In the 1990s, a group of scientists studying the tuatara on this island noticed that there were more males than females (60% males). The scientists started collecting data on the number of males and females so they could track whether the sex ratio, or the ratio of males and females in the population, became more balanced or became even more male-biased over time. The sex ratio is important because when there are fewer females in a population, there are fewer individuals that lay eggs and produce future offspring. Generally, a population that is highly male-biased will have lower reproduction rates than a population that is more balanced or is female-biased.

The fact that tuatara are long-lived and breed infrequently meant that the scientists needed to follow the sex ratio for many years to be sure they were capturing a true shift in the sexes over time, not just a short-term variation. In 2012, Kristine and her colleagues decided to use these long-term data to see if the increasing temperatures from climate change were associated with the changing sex ratio. They predicted that there would be a greater proportion of males in the population over time. This would be reflected in an unbalanced sex ratio that is moving further and further away from 50% males and 50% females and toward a male-biased population.

Featured scientists: Kristine Grayson from University of Richmond, Nicola Mitchell from University of Western Australia, and Nicola Nelson from Victoria University of Wellington

Flesch–Kincaid Reading Grade Level = 11.9

Additional teacher resources related to this Data Nugget:

Video Recording from Headwaters Institute: Lunch with a scientist – Meet Dr. Kristine Grayson!
Want to learn more about tuatara or introduce students to this species before beginning the Data Nugget? Check out this video by “It’s ok to be smart”.
There are two publications associated with the research in this activity:
- Grayson, Kristine L., Nicola J. Mitchell, Joanne M. Monks, Susan N. Keall, Joanna N. Wilson, and Nicola J. Nelson (2014). Sex Ratio Bias and Extinction Risk in an Isolated Population of Tuatara (Sphenodon punctatus). PLoS ONE 9(4): e94214.
- Grayson, Kristine L., Nicola J. Mitchell, and Nicola J. Nelson (2014). A Threat to New Zealand’s Tuatara Heats Up. American Scientist 102: 350-357.
For a popular science article about tuatara research, written for students, check out Science News for Student’s article “When a species can’t stand the heat: Global warming could leave New Zealand’s tuatara dangerously short of females” (PDF for printing, Word Search!)
Students can access the National Institute of Water and Atmospheric Research (NIWA) New Zealand weather station data here.

About Kristine: Kristine L. Grayson is an Associate Professor in the Biology Department at University of Richmond, where she teaches Intro Ecology/Evolution, Field Ecology, Ecophysiology, and Data Visualization. She is an HHMI BioInteractive Ambassador and facilitator with the Quantitative Undergraduate Biology Education and Synthesis (QUBES) project, where you can find additional teaching resources she has authored. Kristine runs an undergraduate research lab studying invasive insects, salamanders, and aquatic macroinvertebrates. Her work on tuatara was conducted during a postdoc at Victoria University of Wellington funded by an NSF International Research Fellowship. One of her claims to fame is capturing the state record holding snapping turtle for North Carolina – 52 pounds! To read more about Kristine and her interest in science from a young age, check out this article.

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6.1.16

The Arctic is Melting – So What?

A view of sea ice in the Artic Ocean.

The activities are as follows:

Think of the North Pole as one big ice cube – a vast sheet of ice, only a few meters thick, floating over the Arctic Ocean. Historically, the amount of Arctic sea ice would be at a maximum in March. The cold temperatures over the long winter cause the ocean water to freeze and ice to accumulate. By September, the warm summer temperatures cause about 60% of the sea ice to melt every year. With global warming, more sea ice is melting than ever before. If more ice melts in the summer than is formed in the winter, the Arctic Ocean will become ice-free, and would change the Earth as we know it.

Student drills through lake ice

This loss of sea ice can have huge impacts on Arctic species and can also affect climate around the globe. For example, polar bears stand on the sea ice when they hunt. Without this platform they can’t catch their prey, leading to increased starvation. Beyond the Arctic, loss of sea ice can increase global climate change through the albedo effect (or the amount of incoming solar radiation that is reflected by a surface). Because ice is so white, it has high albedo and reflects a lot of the sunlight that hits it and keeps the earth cooler. Ice’s high albedo is why it seems so bright when the sun reflects off snow. When the ice melts and is replaced by water, which has a much lower albedo, more sunlight is absorbed by the earth’s surface and temperatures go up.

Scientists wanted to know whether the loss of sea ice and decreased albedo could affect extreme weather in the northern hemisphere. Extreme weather events are short-term atmospheric conditions that have been historically uncommon, like a very cold winter or a summer with a lot of rain. Extreme weather has important impacts on humans and nature. For example, for humans, extreme cold requires greater energy use to heat our homes and clear our roads, often increasing the use of fossil fuels. For wildlife, extreme cold could require changes in behavior, like finding more food, building better shelter, or a moving to a warmer location.

Student releases weather balloon

To make predictions about how the climate might change in the coming decades to centuries, scientists use climate models. Models are representations, often simplifications, of a structure or system used to make predictions. Climate models are incredibly complex. For example, climate models must describe, through mathematical equations, how water that evaporates in one region is transferred through the atmosphere to another region, potentially hundreds of miles away, and falls to the ground as precipitation.

James is a climate scientist who, along with his colleagues, wondered how the loss of arctic sea ice would affect climates around the globe. He used two well-established climate models – (1) the UK’s Hadley Centre model and (2) the US’s National Center for Atmospheric Research model. These models have been used previously by the Intergovernmental Panel on Climate Change (IPCC) to predict how much sea ice to expect in 2100.

Featured scientists: James Screen from University of Exeter, Clara Deser from National Center for Atmospheric Research, and Lantao Sun from University of Colorado at Boulder. Written by Erin Conlisk from Science Journal for Kids.

Flesch–Kincaid Reading Grade Level = 10.2

This Data Nugget was adapted from a primary literature activity developed by Science Journal For Kids. For a more detailed version of this lesson plan, including a supplemental reading, videos, and extension activities, visit their website and register for free!

There is one scientific paper associated with the data in this Data Nugget. The citation and PDF of the paper is below.

Screen J.A., Deser C., Sun L. 2015. Projected changes in regional climate extremes arising from Arctic sea ice loss. Environmental Research Letters 10: 084006.
The same paper, written at a middle/high school reading level by Science Journal for Kids, can be found here.

You can play this video, showing changes in Arctic sea ice from 1987-2014, overhead at the start of class (no sound required). Each student should write down a couple of observations and questions.

4.20.16

The birds of Hubbard Brook, Part II

In Part I, you examined patterns of total bird abundance at Hubbard Brook Experimental Forest. These data showed bird numbers at Hubbard Brook have declined since 1969. Is this true for every species of bird? You will now examine data for four species of birds to see if each of these species follows the same trend.

Red-eyed vireo in the Hubbard Brook Experimental Forest

The activities are as follows:

It is very hard to study migratory birds because they are at Hubbard Brook only during their breeding season (summer in the Northern Hemisphere). They spend the rest of their time in the southeastern United States, the Caribbean or South America or migrating between their two homes. Therefore, it can be difficult to tease out the many variables affecting bird populations over their entire range. To start, scientists decided to focus on what they could study—the habitat types at Hubbard Brook and how they might affect bird populations.

Hubbard Brook Forest was heavily logged and disturbed in the early 1900s. Trees were cut down to make wood products, like paper and housing materials. Logging ended in 1915, and various plants began to grow back. The area went through what is called secondary succession, which refers to the naturally occurring changes in forest structure that happen as a forest recovers after it was cut down or otherwise disturbed. Today, the forest has grown back. Scientists know that as the forest grew older, its structure changed: Trees grew taller, the types of trees changed, and there was less shrubby understory. The forest now contains a mixture of deciduous trees that lose their leaves in the winter (about 80–90%; mostly beech, maples, and birches) and evergreen trees, mostly conifers, that stay green all year (about 10–20%; mostly hemlock, spruce, and fir).

Richard and his fellow scientists already knew a lot about the birds that live in the forest. For example, some bird species prefer habitats found in younger forests, while others prefer habitats found in older forests. They decided to look carefully into the habitat preferences of four important species of birds—Least Flycatcher, Red-eyed Vireo, Black-throated Green Warbler, and American Redstart—and compare them to habitats available at each stage of succession. They wondered if habitat preference of a bird species is associated with any change in the bird populations at Hubbard Brook since the beginning of succession.

Least Flycatcher: The Least Flycatcher prefers to live in semi-open, mid-successional forests. The term mid-successional refers to forests that are still growing back after a disturbance. These forests usually consist of trees that are all about the same age and have a thick canopy at the top with few gaps, a relatively open area under the canopy, and a denser shrub layer close to the ground.
Black-throated Green Warbler: The Black-throated Green Warbler occupies a wide variety of habitats. It seems to prefer areas where deciduous and coniferous forests meet and can be found in both forest types. It avoids disturbed areas and forests that are just beginning succession. This species prefers both mid-successional and mature forests.
Red-eyed Vireo: The Red-eyed Vireo breeds in deciduous forests as well as forests that are mixed with deciduous and coniferous trees. They are abundant deep in the center of a forest. They avoid areas where trees have been cut or blown down and do not live near the edge. After an area is logged, it often takes a very long time for this species to return.
American Redstart: The American Redstart generally prefers moist, deciduous, forests with many shrubs. Like the Least Flycatcher, this species prefers mid-successional forests.

Featured scientist: Richard Holmes from the Hubbard Brook Experimental Forest. Data Nugget written by: Sarah Turtle and Jackie Wilson.

Flesch–Kincaid Reading Grade Level = 10.6

A view of the Hubbard Brook Experimental Forest

Additional teacher resource related to this Data Nugget:

There is an engaging video that can be used before the students begin the activity. It introduces some of the researchers behind this body of work, including Richard Holmes, and highlights the importance of the long-term nature of this dataset.
For the full dataset associated with this Data Nugget, check out the Hubbard Brook Data Catalog page. Search for “Bird abundances” in the search bar to find the dataset.
For more information on this research, check out the Hubbard Brook Experimental Forest’s page on their songbird research
For more lessons created from data collected on birds at Hubbard Brook, check out the page “Migratory Birds Math and Science Lessons from Hubbard Brook.”

There are multiple publications related to the data included in this activity:

Holmes, R. T. 2011. Birds in northern hardwoods ecosystems: Long-term research on population and community processes in the Hubbard Brook Experimental Forest. Forest Ecology and Management doi:10.1016/j.foreco.2010.06.021.
Holmes, R.T., 2007. Understanding population change in migratory songbirds: long-term and experimental studies of Neotropical migrants in breeding and wintering areas. Ibis 149 (Suppl. 2), 2-13.
Townsend, A. K., et al. (2016). The interacting effects of food, spring temperature, and global climate cycles on population dynamics of a migratory songbird. Global Change Biology 2: 544-555.

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4.20.16

The birds of Hubbard Brook, Part I

Male Black-throated Blue Warbler feeding nestlings. Nests of this species are built typically less than one meter above ground in a shrub such as hobblebush. Photo by N. Rodenhouse.

The activities are as follows:

The Hubbard Brook Experimental Forest is an area where scientists have collected ecological data for many years. It is located in the White Mountains of New Hampshire. Data collected in this forest helps uncover environmental trends over long periods of time, such as changes in air temperature, precipitation, forest growth, and animal populations. It is important to collect data on ecosystems over time because these patterns could be missed with shorter observation periods or short-term experiments.

Richard Holmes is an avian ecologist who began this study because he was interested in how bird populations were responding to long-term environmental change.

Each spring, Hubbard Brook comes alive with the arrival of migratory birds. Many come from the tropics to take advantage of abundant insects and the long summer days of northern areas. In the spring, avian ecologists, or scientists who study the ecology of birds, also become active in the forest at Hubbard Brook. They have been keeping records on the birds that live in the experimental forest for over 50 years. These data are important because they represent one of the longest bird studies ever conducted!

Richard is an avian ecologist who began this study early in his career as a scientist. He was interested in how bird populations respond to long-term environmental changes at Hubbard Brook. Every summer since 1969, Richard takes his team of trained scientists, students, and technicians into the field to identify which species are present. Richard’s team monitors populations of over 30 different bird species. They count the number of birds that are in the forest each year and study their activities during the breeding season. The researchers wake up every morning before the sun rises and travel to the far reaches of the forest. They listen for, look for, identify, and count all the birds they find. The team has been trained to be able to identify the birds by sight, but also by their calls. Team members are even able to identify how far away a bird is by hearing its call!

The study area is located away from any roads or other disturbed areas. To measure the abundance, or number of birds found in the 10 hectare study area, the researchers used what is called the spot-mapping method. They use plastic flags on trees 50 meters apart throughout the study area to create a 50×50 meter grid. The grid allows them to map where birds are found in this area, and when possible, where they locate their nests. Using the grid the researchers systematically walk through the plot several days each week from early May until July, recording the presence and activities of every bird they find. They also note the locations of nearby birds singing at the same time. These records are combined on a map to figure out a bird’s territory, or activity center. At the end of the breeding season they count up the number of territories to get an estimate of the number of birds on the study area. This information, when paired with observations on the presence and activities of mates, locations of nests, and other evidence of breeding activity provide an accurate estimate for bird abundance. Finally, some species under close study, like American Redstart and Black-throated Blue Warbler, were captured and given unique combinations of colored bands, which makes it easier to track individuals.

By looking at bird abundance data across many years, Richard and his colleagues can identify trends that reveal how avian populations change over time.

Featured scientist: Richard Holmes from the Hubbard Brook Experimental Forest. Data Nugget written by: Sarah Turtle and Jackie Wilson.

Flesch–Kincaid Reading Grade Level = 11.3

A view of the Hubbard Brook Experimental Forest

Additional teacher resource related to this Data Nugget:

There is an engaging video that can be used before the students begin the activity. It introduces some of the researchers behind this body of work, including Richard Holmes, and highlights the importance of the long-term nature of this dataset.
For the full dataset associated with this Data Nugget, check out the Hubbard Brook Data Catalog page. Search for “Bird abundances” in the search bar to find the dataset.
For more information on this research, check out the Hubbard Brook Experimental Forest’s page on their songbird research
For more lessons created from data collected on birds at Hubbard Brook, check out the page “Migratory Birds Math and Science Lessons from Hubbard Brook.”

There are multiple publications related to the data included in this activity:

Holmes, R. T. 2011. Birds in northern hardwoods ecosystems: Long-term research on population and community processes in the Hubbard Brook Experimental Forest. Forest Ecology and Management doi:10.1016/j.foreco.2010.06.021.
Holmes, R.T., 2007. Understanding population change in migratory songbirds: long-term and experimental studies of Neotropical migrants in breeding and wintering areas. Ibis 149 (Suppl. 2), 2-13.
Townsend, A. K., et al. (2016). The interacting effects of food, spring temperature, and global climate cycles on population dynamics of a migratory songbird. Global Change Biology 2: 544-555.

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3.25.16

Keeping up with the sea level

A view of salt marsh hay (Spartina patens) growing in a marsh

The activities are as follows:

Salt marshes are ecosystems that occur along much of the coast of New England in the United States. Salt marshes are very important – they serve as habitat for many species, are a safer breeding location for many fish, absorb nutrients from fertilizer and sewage coming from land and prevent them from entering the ocean, and protect the coast from erosion during storms.

Unfortunately, rising sea levels are threatening these important ecosystems. Sea level is the elevation of the ocean water surface compared to the elevation of the soil surface. Two processes are causing sea levels to rise. First, as our world gets warmer, ocean waters are getting warmer too. When water warms, it also expands. This expansion causes ocean water to take up more space and it will continue to creep higher and higher onto the surrounding coastal land. Second, freshwater frozen in ice on land, such as glaciers in Antarctica, is now melting and running into the oceans. Along the New England coast, sea levels have risen by 0.26 cm a year for the last 80 years, and by 0.4 cm a year for the last 20 years. Because marshes are such important habitats, scientists want to know whether they can keep up with sea level rise.

Researcher Sam Bond taking Sediment Elevation Table (SET) measurements in the marsh

When exploring the marsh, Anne, a scientist at the Plum Island Ecosystems Long Term Ecological Research site, noticed that the salt marsh appeared to be changing over time. One species of plant, salt marsh cordgrass (Spartina alterniflora), appeared to be increasing in some areas. At the same time, some areas with another species of plant, salt marsh hay (Spartina patens), appeared to be dying back. Each of these species of plants is growing in the soil on the marsh floor and needs to keep its leaves above the surface of the water. As sea levels rise, the elevation of the marsh soil must rise as well so the plants have ground high enough to keep them above sea level. Basically, it is like a race between the marsh floor and sea level to see who can stay on top!

Anne and her colleges measured how fast marsh soil elevation was changing near both species of plants. They set up monitoring points in the marsh using a device called the Sediment Elevation Table (SET). SET is a pole set deep in the marsh that does not move or change in elevation. On top of this pole there is an arm with measuring rods that record the height of the marsh surface. The SETs were set up in 2 sites where there is salt marsh cordgrass and 2 sites where there is salt marsh hay. Anne has been taking these measurements for more than a decade. If the marsh surface is rising at the same rate as the sea, perhaps these marshes will continue to do well in the future.

Featured scientist: Anne Giblin from the Marine Biological Laboratory and the Plum Island Ecosystems Long-Term Ecological Research site

Flesch–Kincaid Reading Grade Level = 9.1

Additional resources related to this Data Nugget:

New research on salt marshes in Massachusetts finds they may actually thrive despite higher water levels. How is this possible? The answer has to do with sediment. Share this article with students after they complete the Data Nuggets activity, discussing research led by Brian Yellen.

3.18.16

Does sea level rise harm Saltmarsh Sparrows?

Painting of the saltmarsh sparrow

The activities are as follows:

For the last 100 years, sea levels around the globe have increased dramatically. The cause of sea level rise has been investigated and debated. Data from around the world supports the hypothesis that increasing sea levels are a result of climate change caused by the burning of fossil fuels. As we warm the Earth, the oceans get warmer and polar ice caps melt. The dramatic increase in sea level that results could seriously threaten ecosystems and the land that humans have developed along the coast.

Salt marshes are plains of grass that grow along the east coast of the United States and many coasts worldwide. Salt marshes grow right at sea level and are therefore very sensitive to sea level rise. In Boston Harbor, Massachusetts, the NOAA (National Oceanic and Atmospheric Administration) Tide Gauge has measured a 21mm rise in sea level over the last 8 years. That means every year sea level has gone up an average of 2.6mm since 2008 – more than two and a half times faster than before we started burning fossil fuels! Because sea level is going up at such a fast rate, Robert, a scientist in Boston, became concerned for the local salt marsh habitats near his home. Robert was curious about what will happen to species that depend on Boston’s Plum Island Sound salt marshes when sea levels continue to rise.

Robert preparing his team for a morning of salt marsh bird surveys.

Robert decided to look at species that are very sensitive to changes in the salt marsh. When these sensitive species are present, they indicate the marsh is healthy. When these species are no longer found in the salt marsh, there might be something wrong. The Saltmarsh Sparrow is one of the few bird species that builds its nests in the salt marsh, and is totally dependent on this habitat. Saltmarsh Sparrows rely completely on salt marshes for feeding and nesting, and therefore their numbers are expected to decline as sea levels rise and they lose nesting sites. Robert heard that scientists studying Connecticut marshes reported the nests of these sparrows have been flooded in recent years. He wanted to know if the sparrows in Massachusetts were also losing their nests because of high sea levels.

For the past two decades Robert has kept track of salt marsh breeding birds at Plum Island Sound. In his surveys since 2006, Robert counted the number of Saltmarsh Sparrows in a given area. He did these surveys in June when birds are most likely to be breeding. He used the “point count” method – standing at a center point he measured out a 100 meter circle around him. Then, for 10 minutes, he counted how many and what kinds of birds he saw or heard within and just outside the circle. Each year he set up six count circles and performed counts three times in June each year at each circle. Robert also used sea level data from Boston Harbor that he can relate to the data from his bird surveys. He predicted that sea levels would be rising in Plum Island Sound and Saltmarsh Sparrow populations would be falling over time.

Featured scientist: Robert Buchsbaum from Mass Audubon. Written by: Wendy Castagna, Daniel Gesin, Mike McCarthy, and Laura Johnson

Flesch–Kincaid Reading Grade Level = 9.5

Additional teacher resources related to this Data Nugget include:

A PDF of the 2014 overview report on the Saltmarsh Habitat and Avian Research Program (SHARP) for the east coast marshes from Maine down to Maryland, which includes Massachusetts. The report may be helpful for students as they come up with other research questions.
A blog by SHARP, covering a wide diversity of salt marsh research!
Data from the Plum Island Sound LTER project.
Data from NOAA tide gauges in Boston Harbor. This dataset expands on that found in Table 1. Students can explore long-term data for Boston Harbor, or can explore other areas for independent research.
For more Boston Harbor tide information, or to look up tides in their area, students can also explore Tideschart.

1.12.16

What do trees know about rain?

A cypress pine, or Callitris columellaris. This species is able to survive in Australia’s dry climates.

The activities are as follows:

Did you know that Australia is the driest inhabited continent in the world? Because it is so dry, we need to be able to predict how often and how much rain will fall. Predictions about future droughts help farmers care for their crops, cities plan their water use, and scientists better understand how ecosystems will change. The typical climate of arid northwest Australia consists of long drought periods with a few very wet years sprinkled in. Scientists predict that climate change will cause these cycles to become more extreme – droughts will become longer and periods of rain will become wetter. When variability is the norm, how can scientists tell if the climate is changing and droughts and rain events today are more intense than what we’ve seen in the past?

To make rainfall predictions for the future, scientists need data on past rainfall. However, humans have only recorded rainfall in Australia for the past 100 years. Because climate changes slowly and goes through long-term cycles, scientists need very long term datasets of rainfall.

Scientist Alison coring a cypress pine

The answer to this challenge comes from trees! Using dendrochronology, the study of tree rings, scientists get a window back in time. Many tree species add a ring to their trunks every year. The width of this ring varies from year to year depending on how much water is available. If it rains a lot in a year, the tree grows relatively fast and ends up with a wide tree ring. If there isn’t much rain in a year, the tree doesn’t grow much and the ring is narrow. We can compare the width of rings from recent years to the known rain data humans have collected. Then, assuming the same forces that determine tree ring width are operating today as in the past, we can go back and interpret how much rain fell in years where we have no recorded rainfall data. This indirect information from tree rings is known as a proxy, and helps us infer data about past climates.

For this study, the scientists used cypress-pine, or Callitris columellaris. This species is able to survive in Australia’s dry climates and is long lived enough to provide data far back in time. Fortunately, scientists don’t have to cut down the trees to see their rings. Instead, they use a corer – a hollow metal drill with the diameter of a straw. They drill it through the tree all the way to its core, and extract a sample of the tissue that shows all the tree rings. The scientists took 40 cores from 27 different cypress-pine trees. The oldest trees in the sample were more than 200 years old. Next, they developed a chronology where they lined up ring widths from one tree with all the other trees, wide with wide and narrow with narrow. This chronology gives them many replicate samples, and data going back all the way to the 19th century! Next, they used a dataset of rainfall from rain gauges that have been set out in Australia since 1910. They then take this precipitation data and overlay it with the tree ring widths since 1910. For tree rings before 1910, they then project back in time using a rainfall formula.

These videos, demonstrating the science of dendrochronology, could be a great way to spark class discussions:

Featured scientist: Alison O’Donnell from University of Western Australia

Flesch–Kincaid Reading Grade Level = 8.0

There is one scientific paper associated with the data in this Data Nugget. The citation and PDF of the paper is below.

O’Donnell, A.J., E.R. Cook, J.G. Palmer, C.S.M. Turney, G.F.M. Page, and P.F. Grierson (2015). Tree Rings Show Recent High Summer-Autumn Precipitation in Northwest Australia Is Unprecedented within the Last Two Centuries. PLoS ONE 10(6) e0128533.
The same paper, written at a middle/high school reading level by Science Journal for Kids, can be found here.

Growth rings from a Callitirs tree.

10.21.15

Is your salt marsh in the zone?

Scientist James collecting plants in a Massachusetts marsh, part of the Plum Island Ecosystems Long Term Ecological Research site

The activities are as follows:

Tides are the rise and fall of ocean water levels, and happen every day like clockwork. Gravity from the moon and sun drive the tides. There is a high tide and a low tide, and the average height of the tide is called the mean sea level. The mean sea level changes seasonally due to the warming and cooling of the ocean throughout the year. It also changes annually due to a long-term trend of ocean warming and the melting of glaciers. Scientific evidence shows that climate change is causing the sea level to rise faster now than it has in the past. As the climate continues to warm, it is predicted that the sea level will continue to rise.

Salt marshes are wetlands with plains of grass that grow along much of the ocean’s coast worldwide. These marshes are important habitats for many plants and animals, and protect our shores from erosion during storms. They grow between mean sea level and the level of high tide. Marshes flood during high tide and are exposed to the air during low tide. The health of a salt marsh is determined by where it sits relative to the tide (the “zone”). A healthy marsh is flooded only part of the time. Too much flooding and too little flooding are unhealthy. Because they are so important, scientists want to know if salt marshes will keep up with sea level rise caused by climate change.

A picture of James’ “marsh organ” which holds plants at different elevations relative to mean sea level. He gave it that name because it resembles organ pipes!

In the 1980s, scientist James began measuring the growth of marsh grasses. He was surprised to find that there was a long-term trend of increasing grass growth over the years. James wanted to know if grasses could continue to keep up with rising sea levels. If he could experimentally manipulate the height of the grasses, relative to mean sea level, he might be able to figure out how grasses will do when sea levels are higher. To test this, James invented a way to experimentally grow a marsh at different elevations relative to mean sea level. He built a device he called the “marsh organ”. This device is made of tubes that stand at different elevations and are filled with marsh mud and planted with marsh grasses. He measured the growth of the grass in each of the pipes. If grasses will continue to grow taller in the future with higher water levels, then plants growing in pipes at lower elevations should grow more than plants growing in pipes with higher elevations.

Featured scientist: James Morris from the University of South Carolina

Additional teacher resource related to this Data Nugget: Jim has created an interactive salt marsh model called the “marsh equilibrium model”. This online tool allows you to plug in different marsh levels to explore potential impacts to the salt marsh. To explore this tool click here.

To read more about Jim’s research on “tipping points” beyond which sediment accumulation fails to keep up with rising sea level and the marshes drown, click here.

There are two publications related to the data included in this activity:

Morris, J.T., Sundberg, K., and Hopkinson, C.S. 2013. Salt marsh primary production and its responses to relative sea level and nutrients in estuaries at Plum Island, Massachusetts, and North Inlet, South Carolina, USA. Oceanography 26:78-84.
Morris, J.T., P.V. Sundareshwar, C.T. Nietch, B. Kjerfve, D.R. Cahoon. 2002. Responses of coastal wetlands to rising sea level. Ecology 83:2869-2877.

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10.20.15

Invasion meltdown

A flower of the invasive plant, Centaurea stoebe (spotted knapweed).

The activities are as follows:

Humans are changing the earth in many ways. First, by burning fossil fuels and adding greenhouse gasses to the atmosphere we are causing climate change, or the warming of the planet. Scientists have documented rising temperatures across the globe and predict an increase of 3° C in Michigan within the next 100 years. Second, we are also changing the earth by movingspecies across the globe, introducing them into new habitats. Some of these introduced species spread quickly and become invasive. Invasive species harm native species and cost us money. There is also potential that these two changes could affect one another; warmer temperatures from climate change may make invasions by plants and animals even worse.

All living organisms have a range of temperatures they are able to survive in, and temperatures where they perform their best. For example, arctic penguins do best in the cold, while tropical parrots prefer warmer temperatures. The same is true for plants. Depending on the temperature preferences of a plant species, warming temperatures may either help or harm that species.

Katie, Mark, and Jen are scientists concerned that invasive species may do better in the warmer temperatures caused by climate change. There are several reasons they expect that invasive species may benefit from climate change. First, because invasive species have already survived transport from one habitat to another, they may be species that are better able to handle change, like temperature increases. Second, the new habitat of an invasive species may have temperatures that allow it to survive, but are too low for the invasive species to do their absolute best. This could happen if the invasive species was transported from somewhere warm to somewhere cold. Climate change could increase temperatures enough to put the new habitat in the species’range of preferred temperatures, making it ideal for the invasive species to grow and survive.

A view of the plants growing in a heated ring.
Notice the purple flowers of Centaurea stoebe.

To determine if climate change will benefit invasive species, Katie, Mark, and Jen focused on one of the worst invasive plants in Michigan, spotted knapweed. They looked at spotted knapweed plants growing in a field experiment with eight rings. Half of the rings were left with normal, ambient air temperatures. The other half of the rings were heated using ceramic heaters attached to the side of the rings. These heaters raised air temperatures by 3° C to mimic future climate change. At the end of the summer, Mark and Katie collected all of the spotted knapweed from the rings. They recorded both the (1) abundance, or number of spotted knapweed plants within a square meter, and (2) the biomass (dry weight of living material) of spotted knapweed. These two variables taken together are a good measure of performance, or how well spotted knapweed is doing in both treatments.

Featured scientists: Katie McKinley, Mark Hammond, and Jen Lau from Michigan State University

Flesch–Kincaid Reading Grade Level = 10.0