Lizards, Iguanas, and Snakes! Oh My!

The Common Side-blotched Lizard

The Common Side-blotched Lizard

The activities are as follows:

Throughout history people have settled mainly along rivers and streams. Easy access to water provides resources to support many people living in one area. In the United States today, people have settled along 70% of rivers.

Today, rivers are very different from what they were like before people settled near them. The land surrounding these rivers, called riparian habitats, has been transformed into land for farming, businesses, or housing for people. This urbanization has caused the loss of green spaces that provide valuable services, such as water filtration, species diversity, and a connection to nature for people living in cities. Today, people are trying to restore green spaces along the river to bring back these services. Restoration of disturbed riparian habitats will hopefully bring back native species and all the other benefits these habitats provide.

Scientist Mélanie searching for reptiles in the Central Arizona-Phoenix LTER.

Scientist Mélanie searching for reptiles in the Central Arizona-Phoenix LTER.

Scientists Heather and Mélanie are researchers with the Central Arizona-Phoenix Long-Term Ecological Research (CAP LTER) project. They want to know how restoration will affect animals living near rivers. They are particularly interested in reptiles, such as lizards. Reptiles play important roles in riparian habitats. Reptiles help energy flow and nutrient cycling. This means that if reptiles live in restored riparian habitats, they could increase the long-term health of those habitats. Reptiles can also offer clues about the condition of an ecosystem. Areas where reptiles are found are usually in better condition than areas where reptiles do not live.

Heather and Mélanie wanted to look at how disturbances in riparian habitats affected reptiles. They wanted to know if reptile abundance (number of individuals) and diversity (number of species) would be different in areas that were more developed. Some reptile species may be sensitive to urbanization, but if these habitats are restored their diversity and abundance might increase or return to pre-urbanization levels. The scientists collected data along the Salt River in Arizona. They had three sites: 1) a non-urban site, 2) an urban disturbed site, and 3) an urban rehabilitated site. They counted reptiles that they saw during a survey. At each site, they searched 21 plots that were 10 meters wide and 20 meters long. The sites were located along 7 transects, or paths measured out to collect data. Transects were laid out along the riparian habitat of the stream and there were 3 plots per transect. Each plot was surveyed 5 times. They searched for animals on the ground, under rocks, and in trees and shrubs.

Featured scientists: Heather Bateman and Mélanie Banville from Arizona State University. Written by Monica Elser from Arizona State University.

Meet the scientist! Click here to watch a video where scientist Heather explains her research!

Flesch–Kincaid Reading Grade Level = 9.8

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

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 they happen every day like clockwork. Gravity from the moon and sun drives 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 seasonal warming and cooling of the ocean, and annually due to the melting of glaciers and a long-term trend of ocean warming. The scientific evidence shows that sea level is rising 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 plains of grass that grow along much of the ocean’s coast worldwide. They grow between mean sea level and the level of high tide. Marshes flood during high tide, and are exposed to the air when the tide goes out. 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. Scientists wanted to know, can salt marshes keep up with current rates of sea level rise or will they loose their balance between high and low tides once sea levels are higher? How can this be measured?

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!

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 Morris began measuring the growth of marsh grasses. He was surprised to discover that marsh grass growth was rising and falling every year, depending on mean sea level, and that there also was a long-term trend of increasing plant growth. Plant growth was greatest in years when the annual mean sea level was unusually high. He wanted to know whether marsh plants could continue this growth and handle rising sea levels. He thought that the long-term trend of increasing plant growth was symptomatic of the marsh surface not rising fast enough to keep up with increasing rates of sea-level rise. If this is the case, plants are growing the most in years where mean sea level is high to stay above the water surface. To test this, James measured elevations of the marsh surface every year and compared this with the elevation of mean sea level. He also made these same measurements in another marsh to determine if the patterns originally observed could be repeated.

James devised a method of growing a marsh at different elevations within the vertical range of the tides. He invented a device that he called the “marsh organ” which is made from PVC pipes that stand at different elevations and are filled with marsh mud and planted with marsh vegetation. The marsh organ design allowed him to experimentally control the elevation. He then measured the growth of the vegetation in the pipes. If higher water levels stimulated growth, then pipes at lower elevations should support more plant growth than pipes 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.

Invasion Meltdown: Will Climate Change Make Invasions Even Worse?

The invasive plant, Centaurea stoebe

The invasive plant, Centaurea stoebe

The activities are as follows:

Humans are changing the earth in many ways, including warming the planet by burning fossil fuels and adding greenhouse gasses to the atmosphere. Scientists have documented rising temperatures across the globe and predict an increase of 3° C in Michigan within the next 100 years. Humans are also changing the earth by transporting species across the globe, introducing them into new habitats. These introduced species may cause problems in their new habitats. Additionally, increasing temperature from climate change may change the way that native and introduced plants and animals interact.

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 due to climate change may either help or harm that species.

Scientists collecting abundance and performance data on the plants in the heating rings.

Scientists collecting abundance and performance data on the plants in the heating rings.

Scientists are concerned that invasive species may do better in the warmer temperatures caused by climate change. Invasive species have been introduced from one area into another, and now thrive in their new habitat. Invasive species harm native species and cause many problems for humans. There are several reasons to 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, such as temperature changes. 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.

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, scientists at Michigan State University focused on one of the worst invasive plants in Michigan, Centaurea stoebe (spotted knapweed). They looked at Centaurea 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 successfully raised air temperatures by 3° C. At the end of the summer, the scientists collected all of the Centaurea plants from the rings. They recorded both the (1) abundance, or number of Centaurea plants within a square meter, and (2) the biomass (dry weight of living material) of the plants in a square meter as a measure of performance.

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

Flesch–Kincaid Reading Grade Level = 8.6

Urbanization and Estuary Eutrophication

Charles Hopkinson out taking dissolved O2 measurements.

Charles Hopkinson out taking dissolved O2 measurements.Student activity, Graph Type A, Level 4

The activities are as follows:

An estuary is a habitat formed where a freshwater river or stream meets a saltwater ocean. Many estuaries can be found along the Atlantic coast of North America. Reeds and grasses are the dominant type of plant in estuaries because they are able to tolerate and grow in the salty water. Where these reeds and grasses grow they form a special habitat called a salt marsh. Salt marshes are important because they filter polluted water and buffer the land from storms. Salt marshes are the habitat for many different kinds of plants, fish, shellfish, and birds.

Hap Garritt removing an oxygen logger from Middle Road Bridge in winter.

Hap Garritt removing an oxygen logger from Middle Road Bridge in winter.

Scientists are worried because some salt marshes are in trouble! Runoff from rain washes nutrients, usually from lawn fertilizers and agriculture, from land and carries them to estuaries. When excess nutrients, such as nitrogen or phosphorus, enter an ecosystem the natural balance is disrupted. The ecosystem becomes more productive, called eutrophication. Eutrophication can cause major problems for estuaries and other habitats.

With more nutrients in the ecosystem, the growth of plants and algae explodes. During the day, algae photosynthesize and release O2 as a byproduct. However, excess nutrients cause these same algae grow densely near the surface of the water, decreasing the light available to plants growing below the water on the soil surface. Without light, the plants die and are broken down by decomposers. Decomposers, such as bacteria, use a lot of O2 because they respire as they break down plant material. Because there is so much dead plant material for decomposers, they use up most of the O2 dissolved in the water. Eventually there is not enough O2 for aquatic animals, such as fish and shellfish, and they begin to die-off as well.

Two features can be used to identify whether eutrophication is occurring. The first feature is low levels of dissolved O2 in the water. The second feature is when there are large changes in the amount of dissolved O2 from dawn to dusk. Remember, during the day when it’s sunny, photosynthesis converts CO2, water, and light into glucose and O2. Decomposition reverses the process, using glucose and O2 and producing CO2 and water. This means that when the sun is down at night, O2 is not being added to the water from photosynthesis. However, O2 is still being used for decomposition and respiration by animals and plants at night.

The scientists focused on two locations in the Plum Island Estuary and measured dissolved O2 levels, or the amount of O2 in the water. They looked at how the levels of O2 changed throughout the day and night. They predicted that the upper part of the estuary would show the two features of eutrophication because it is located near an urban area. They also predicted the lower part of the estuary would not be affected by eutrophication because it was farther from urban areas.

A view of the Plum Island estuary

A view of the Plum Island estuary

Featured scientists: Charles Hopkinson from University of Georgia and Hap Garritt from the Marine Biological Laboratory Ecosystems Center

Flesch–Kincaid Reading Grade Level = 9.6

Can a salt marsh recover after restoration?

Students collecting salinity data at a transect point. The tall tan grass is Phragmites.

Students collecting salinity data at a transect point. The tall tan grass is Phragmites.

The activities are as follows:

In the 1990s, it was clear that the Saratoga Creek Salt Marsh in Rockport, MA was in trouble. The invasive plant, Phragmites australis, covered large areas of the marsh. The thick patches of Phragmites crowded out native plants and reduced the number of animals, especially migrating birds, because it was too thick to land in. Salt marshes are wetland habitats near ocean coasts that have mostly water-loving, salt-tolerant grasses. Human activity was having a huge effect on the health of the Saratoga Creek Salt Marsh by lowering the salinity, or salt concentrations in the water. Drains built by humans to keep water from rainstorms off the roads changed how water moved through the marsh. The storm drains added a lot of runoff, or freshwater and sediments from the surrounding land, into the marsh after rainstorms. Adding more freshwater to the marsh lowers salinity. The extra sediment that washed into the marsh raised soil levels along the road. If the soil levels get too high, the salty ocean water does not make it into the marsh during high tide. Perhaps these storm drains were changing the salinity of the marshes in a way that helped Phragmites because it grows best when salinity levels are low.

In 1998, scientists, including members of the Rockport Conservation Commission and students from the Rockport Middle School science club, began to look at the problem. They wanted to look at whether freshwater runoff from storm drains may be the reason Phragmites was taking over the marsh. They were curious whether the salinity would increase if they made the storm water drain away from the marsh. They also thought this would stop the runoff sediments from raising soil levels. If so, this could be one way to restore the health of the salt marsh and reduce the amount of Phragmites.

In 1999, a ditch was dug alongside the road to collect runoff from storm drains before it could enter the marsh. A layer of sediment was also removed from the marsh so ocean water could reach the marsh once again. Students set up transects, specific areas chosen to observe and record data. Then they measured the growth and abundances of Phragmites found in these transects. They also measured water salinity levels. Transects were 25 meters long and data were collected every meter. The students decided to compare Phragmites data from before 1999 and after 1999 to see if diverting the water away from the marsh made a difference. They predicted that the number and height of Phragmites in the marsh would go down after freshwater runoff was reduced after restoration.

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View of Saratoga Creek Salt Marsh several years after restoration, showing location of one of the transects. Native grasses are growing in the foreground.

View of Saratoga Creek Salt Marsh several years after restoration, showing location of one of the transects. Native grasses are growing in the foreground.

Featured scientists: Liz Duff from Mass Audubon, Eric Hutchins from NOAA, and Bob Allia and 7th graders from Rockport Middle School

Written by: Bob Allia, Cindy Richmond, and Dave Young

Flesch–Kincaid Reading Grade Level = 9.5

For more information on this project, including datasets and more scientific background, check out their website: Salt Marsh Science

Springing Forward: Does climate change cause plants to flower earlier?

Scientist Shaun collecting phenology data in the climate change experiment. He is recording the date that the first flowers emerge for dame’s rocket.

Sean Mooney, a high school researcher, collecting phenology data in the climate change experiment. He is recording the date that the first flowers emerge for dame’s rocket.

The Reading Level 1 activities are as follows:

The Reading Level 3 activities are as follows:

Every day we add more greenhouse gases to our air by burning fossil fuels, such as oil, coal, and natural gas. Greenhouse gasses trap the sun’s heat, so adding more causes the Earth to heat up!  What does that mean for the species on our planet? The timing of life cycle events for plant and animals, like flowering and migration, are largely determined by cues organisms take from the environment. Scientists studying phenology, or the timing of life cycle events, are interested in how climate change will influence different species. For example, with warming temperatures and unpredictable transitions between seasons, what can we expect to happen to the migration timings of birds, mating seasons for animals, or flowering times of plants?

Scientists collecting phenology data in the climate change experiment. They are recording the date that the first flowers emerge for dame’s rocket.

Scientists collecting phenology data in the climate change experiment.

Plants are the foundation for almost all life on Earth. Through photosynthesis, plants produce O2 that we breathe, food for animals and microbes, and crops that provide food and materials for human society. Because plants are so important, we need to find out how climate change will affect them. One good place to start is by looking at flowering plants. How will increased temperatures affect the phenology of flowering? If the date that flowers first emerge for a species is driven by temperature, then we would expect flowers to emerge earlier when temperatures are higher. If flowers start emerging earlier each year due to climate change, this could greatly impact plant reproduction and could cause problems for pollinators who count on plants flowering at the same times each year.

Scientists Shaun, Mark, Elizabeth, and Jen wanted to know if higher temperatures lead to earlier flowering dates for plants. They chose to look at flowers of dame’s rocket, a leafy plant that is related to the plants we use to make mustard! Mark planted dame’s rocket in eight plots of land. Plots were randomly assigned to one of two treatments. Half of the plots were left to experience normal temperatures (ambient), while the other four received a heating treatment to simulate climate change (heated). Air temperatures in heated plots increased by 3°C, which mimics climate change projections for what Michigan will experience by the end of the century. Mark, Elizabeth, and Jen measured the date that each plant grew its first flower, and the survival of each plant. The scientists predicted that dame’s rocket growing in the heated plots would flower earlier than those in the normal plots.

 Featured scientists: Shaun Davis from Thornapple Kellogg Middle School and Mark Hammond, Elizabeth Schultheis, and Jen Lau from Michigan State University

Flesch–Kincaid Reading Grade Level = The Reading Level 3 activity has a score of 9.8; the Level 1 has a 7.0.

Flowers of Hesperis matronalis (dame’s rocket), a species of mustard that was introduced to the U.S. from Eurasia.

Flowers of Hesperis matronalis (dame’s rocket), a species of mustard that was introduced to the U.S. from Eurasia.

Additional teacher resources related to this Data Nugget include:

  • If you would like your students to interact with the raw data, we have attached the original data here. The file also includes weather data over the course of the experiment if students want to ask and explore independent questions.
  • For a lesson plan that uses citizen science phenology datasets to examine changes in phenology over 30+ year timespans, and address the scientific question, “Do we see evidence for climate change in the phenology of plants and animals?”, click here.
  • Many phenology datasets are freely available online (many collected by citizen scientists). These datasets are extremely useful because scientists (and your students!) can examine average trends in timing shifts over periods of decades and often in different regions. Phenology datasets available online:





Marvelous mud


You can tell that the mud in this picture is high in organic matter because it is dark brown and mucky (in real life you’d be able to smell it, too!)

The activities are as follows:

The goopy, mucky, (sometimes stinky!) mud at the bottom of a wetland or lake is a very important part of the ecosystem. Mud is basically wet soil, but because it has different properties than soil because it is wet most of the time. Mud is usually dark brown because it contains partially decomposed plants, called organic matter. Dead organic matter tends to build up in wetlands. Organic matter decomposes more slowly under water than on land. This is because underwater microbes do not have all the oxygen they need to break it down quickly.

A successful core! You can see that the tube has mud, as well as some of the water from the wetland that was on top of the mud.

A successful core! You can see that the tube has mud, as well as some of the water from the wetland that was on top of the mud.

Under the right conditions, mud can act like fertilizer for a wetland. Nutrients, such as phosphorus, tend to build up in mud. This makes mud an important source of the phosphorus that algae and other plants need to grow. As a graduate student at Michigan State University, scientist Lauren was interested in what helped phosphorus stick to mud. She also wanted to know why phosphorus builds up more in some wetlands than others.

Although most mud is high in organic matter and high in nutrients, all mud is not created equal! The amounts of organic matter and nutrients are different from one ecosystem to the next. How quickly these materials enter or leave the mud may also change across ecosystems. Even within the same ecosystem mud can be very different from place to place. The molecules in organic matter could be a major source of phosphorus in mud. This would mean that wetlands with more organic matter would have more phosphorus.

Scientist Lauren measured organic matter and phosphorus in mud from 16 ecosystems (four lakes, five ponds, and seven wetlands). She wanted to determine if there was a relationship between the amount of organic matter and the amount of phosphorus in mud.

Featured scientist: Lauren Kinsman-Costello from Kent State University

Flesch–Kincaid Reading Grade Level = 8.7

More photos associated with this research can be found here. There is one scientific paper associated with the data in this Data Nugget. The citation and PDF of the paper is below:

Kinsman-Costello LE, J O’Brien, SK Hamilton (2014) Re-flooding a Historically Drained Wetland Leads to Rapid Sediment Phosphorus Release. Ecosystems 17:641-656

Is chocolate for the birds?

Cocoa beans used to make chocolate!

Cocoa beans used to make chocolate!

The activities are as follows:

9,000 years ago humans invented agriculture as a way to grow enough food for people to eat. Today, agriculture happens all over the globe, and takes up 40% of Earth’s land surface! To make space for our food, humans must clear large areas of land, creating a disturbance, or drastic change, to the habitat. This disturbance removes the native plants already there, including trees, small flowering plants, and grasses. Many types of animals including mammals, birds, and insects need these native plants for food or shelter and will now find it difficult to live in the area. For example, a woodpecker bird can’t live somewhere where there are no trees, because they live and find their food in the trees.

However, some disturbances might help some animals because they can use crops for the food and shelter they need to survive. One example is the cacao tree, which grows in the rainforests of South America. Humans use the seeds of this plant to make chocolate, so it is a very important crop! Cacao trees need very little light. They grow best under the large trees found in rainforests. To get lots of cacao seeds for chocolate, farmers need to have large rainforest trees above their cacao trees for shade. In many ways, cacao farms resemble a native rainforest. Many native plant species grow there and there are still taller tree species. However, these farms are different in important ways from a native rainforest. For example, there are many more cacao trees than found in native rainforests. Also, there are fewer small flowering plants on the ground because humans that work on cacao farms trample them as they walk around the farm.

rainforest and cacao plantation

Part I: Skye is a biologist who wanted to know if birds from rainforests could survive when their habitat was replaced with cacao farms. To begin, she counted birds and determined their abundance in each habitat. Skye chose one rainforest and one cacao farm and set up two transects in each. She spent 4 days counting birds along each transect, for a total of 8 days in each habitat. She had to get up really early and count birds between 6:00 and 9:00 in the morning because that’s when they are most active!

Part II: Skye was shocked to see so many birds in cacao farms! She decided to take a closer look at her data. Skye wanted to know whether the types of birds she saw in the cacao farms were different or the same as the birds she saw in the rainforest. She predicted that cacao farms might have different types of birds living in them than the undisturbed rainforest. She thought the bird types would differ because each habitat has different types of food available for birds to eat and different types of plants for birds to live in.

Skye broke her abundance data down to look more closely at four types of birds:

  1. Toucans (Eat: large insects and fruit from large trees, Live: holes in large trees)
  2. Hummingbirds (Eat: nectar from flowers, Live: tree branches and leaves)
  3. Wrens (Eat: small insects, Live: small shrubs on the forest floor)
  4. Flycatchers (Eat: Small insects, Live: tree branches and leaves)


Featured scientist: Skye Greenler from Colorado College

Flesch–Kincaid Reading Grade Level = 8.5

Information on study location: Skye’s study took place in a 10 km2 mixed rainforest, pasture, agro-forest, and monoculture landscape near the village of Pueblo Nuevo de Villa Franca de Guácimo, Limón Province, Costa Rica (10˚20˝ N, 83˚20˝ W), in the Caribbean lowlands 85 km northeast of San José.

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

Greenler, S.M. and J.J. Ebersole (2015) Bird communities in tropical agroforestry ecosystems: an underappreciated conservation resource. Agroforestry Systems 89: 691–704.

Finding a Foothold

The activities are as follows:

Have you ever noticed that the ground at a beach has rocks of many different sizes? These rocks, sand, and dirt are all called substrates. The types of substrate we see are described by the size of the particles that cover the ground. These can range from large boulders down to fine grains of sand and dirt, with many sizes in between. No matter what type of substrate you see at the beach, you can find organisms that will live in or on it. Just like there are different types of substrates, there are different types of organisms that can live there. How can we determine which types of organisms prefer which types of substrates? That is the job of field researchers!


Students collecting mollusk data on different beach substrates.

Students and teachers at Kentridge High School have made many field trips to the beach and have seen lots of organisms. Normally, they just noticed what they could see easily in front of them. Students became interested to know how the type of substrate influences which organisms will live there. They noticed that the snails in the aquarium at school like to stick to the glass walls of the tank. Do snails and other shelled mollusks found near the ocean, like chitons, periwinkles, whelks and limpets, also like to live on large, stable substrates? The students went to beach to find out!

Mollusks have a “foot” which may be able to attach more securely to larger substrates, such as boulders, and allow them more room to move. So, the students expected to find more mollusks on boulders than on other types of substrates. To gather the data needed to answer this question, the students went to a local beach. They looked at sections of the beach with substrates of all types. On these different substrates, they kept track of all the different types of organisms that were present. They measured the frequency that they observed four types of mollusks (chitons, limpets, whelks, and periwinkles) on the following substrates: boulder, gravel, pebble, logs, sand, and shell debris. Frequency was measured as the proportion of times that a particular organism was present on a substrate type, out of the total number of observations. For example, if they observed 2 boulders and saw limpets on 1, the frequency would = ½ or 0.5.

Featured scientists: Darrel Nash and Sarah Hall from Kentridge High School, Washington

Flesch–Kincaid Reading Grade Level = 7.4

For more information on the Seattle Aquarium’s citizen science project, and to download the dataset from this project, click here

Do invasive species escape their enemies?

One of the invasive plants found in the experiment, Dianthus armeria

One of the invasive plants found in the experiment, Dianthus armeria

The activities are as follows:

Invasive species, like zebra mussels and garlic mustard, are species that have been introduced by humans to a new area. Where they invade they cause harm. For example, invasive species outcompete native species and reduce diversity, damage habitats, and interfere with human interests. Damage from invasive species costs the United States over $100 billion per year.

Scientists want to know, what makes an invasive species become such a problem once it is introduced? Is there something that is different for an invasive species compared to native species that have not been moved to a new area? Many things change for an invasive species when it is introduced somewhere new. For example, a plant that is moved across oceans may not bring enemies (like disease, predators, and herbivores) along for the ride. Now that the plant is in a new area with no enemies, it may do very well and become invasive.


Scientists at Michigan State University wanted to test whether invasive species are successful because they have escaped their enemies. They predicted invasive species would get less damage from enemies, compared to native species that still live near to their enemies. If native plants have tons of insects that can eat them, while an invasive plant has few or none, this would support enemy escape explaining invasiveness. However, if researchers find that native and invasive species have the same levels of herbivory, this would no support enemy escape. To test this hypothesis, a lab collected data on invasive and native plant species in Kalamazoo County. They measured how many insects were found on each species of plant, and the percent of leaves that had been damaged by insect herbivores. The data they collected is found below and can be used to test whether invasive plants are successful because they get less damage from insects compared to native plants.

Featured scientist: Elizabeth Schultheis from Michigan State University

Flesch–Kincaid Reading Grade Level = 11.3

  • For a lesson plan on the Enemy Release Hypothesis, click here.
  • For a great scientific paper discussing the Enemy Release Hypothesis, click here.
  • The Denver Museum of Nature and Science has a short video giving background on invasive species, here