Tag Archives: botany

Johanna Schmitt: Climate Change and Plant Life

We sometimes ignore the effects of climate change on plant life, but the potential severity of these effects isn’t something that should be ignored for long (Image Credit: Pisauakan, CC0)

From the California wildfires to the recent strikes across Australian primary schools, climate change is a topic that only seems to grow in its ubiquity. Yet whilst humans are increasingly focused on more obvious repercussions, such as extreme weather events, animal extinctions and shifting coastlines, we sometimes forget that climate change will have severe repercussions for plant life as well.

I spoke to Professor Johanna Schmitt of the University of California earlier this year to discuss some of those repercussions. Johanna’s team is working to determine how well certain plant species will be able to adapt in the face of rapid climate change.

Sam Perrin (SP): The term climate change is ubiquitous these days, yet we often don’t talk about plants in relation to its effects. What will some of the effects of climate change be on plant life?

Professor Johanna Schmitt, Department of Evolution and Ecology, University of California (JS): Well from a North American perspective, let’s start with seasonality. The growing season is longer, spring is coming earlier, summers are hotter, winters are warmer. And so in a lot of temperate areas trees are leafing out earlier. And in colder areas, there’s potential that they won’t be adapting to the warmer weather, and will continue to act on temperature cues, which would be bad. There’s definitely evidence of changes in phenology, in seasonal timing of phylogenic effects. There certainly is already evidence of shifts northward in some plant species, and local extinction of species in their southernmost populations.

Looking at California, we’ve just come out of a mega-drought. We have cyclical droughts, and they’re getting worse because the temperature’s rising. Among other things, it means the snow packs are much lower in California. That means water supplies are lower, because there’s less and less water from the melting snow pack. If precipitation all comes as rain in the winter, then that reservoir of snow is not there, so there’s no water in the summer for the farmers. And that also means the species in the mountains which previously relied on the water from snow melt can’t get through the summer. So we’re seeing pretty massive forest die-offs. And then in addition to that you have the bark beetles, which decimate trees. In parts of the western United States, these bark beetles can produce an extra generation if the winters aren’t cold enough and so the populations expand. I was hiking in the Rocky Mountain National Park a few years ago and the trees had been torn to shreds by these bark beetles.

And off the back of all this we’ve obviously had huge fires. This last fire year in California was record horrible. That’s something that affects plant life that then affects humans big time.

SP: Will the agriculture industry have to start adapting?

JS: There’s a group at Stanford who have been trying to figure out if there’s a signature of temperature affecting crop yields by looking at historical data. And it appears that higher temperatures are affecting crop yields and they expect that to become an issue in the future. This idea that if there’s more carbon dioxide, that will help fertilise the crops and they’ll do fine doesn’t seem to hold if you go beyond critical temperatures. Bottom line is, yes, people are concerned about crop yields being affected.

SP: Things like drought and forest die-off have become more extreme these days. But there’s a danger of this becoming the new norm for people. How do we fight those shifting baselines?

JS: It’s a really interesting concept. Because the younger generation doesn’t remember stuff that my generation does. For kids today, these California wildfires will be the new normal. When I was a little girl growing up outside of Pennsylvania we used to go ice-skating on the ponds all the time after they would freeze in winter. Nobody does that anymore because the ponds don’t freeze.

You look at the record of temperatures. I take Introduction to Biology lectures, and I show the carbon dioxide curve from Mauna Loa in Hawaii, and I show them that when I was born, CO2 was 320 parts per million, and then show them the increase just in their lifetime. So now, being over 400ppm is the new normal. Kids today won’t ever remember it being less than that. People are getting more used to extreme heat events which we just didn’t have 50 years ago.

Arabidopsis thaliana, which Johanna's lab works with, is a handy model species for looking at the effects of climate change on plant life

Arabidopsis thaliana, which Johanna’s lab works with, is a handy model species for looking at the effects of climate change on plant life (Image Credit: Dawid Skalec)

SP: To what extent can we predict the adaptation of some of these species to climate change?

JS: Not very well, that’s really the take-home message. Foresters have the best ability to do that because they’ve been doing large scale trials, taking genotypes from across a species’ range and growing them in different climates across that range. By doing that you can ask how different genotypes perform in different climates. And that allows you to say how much variation is there within the species across the range, and you can also look at how much variation is there within populations. Take something like budset, the timing of when to set your buds and cease growth, shut down, and go dormant so you don’t get killed by the frost. It’s a pretty hard deadline for conifer trees. But from year to year the frost comes at slightly different times. So some years genotypes that are more risk-averse do better and some years others that are more risk-prone do better, so they’d have alternate good years. And this means variation can help a species persist in a changing climate

So for forest trees there may be a fair amount of potential for adaptation. And now people are starting to look at small endemic plant species. Jill Anderson at the University of Georgia has been doing some really interesting work of late on adaptation to elevation across an altitudinal gradient. They combined genotypes at low, medium and high elevations, and combined those mixed gardens with snow manipulation. They either removed or added snow, and they found was evidence of adaptation for the species which were exposed to snow. So that suggested that the population may have trouble keeping up if we have a declining snow pack.

SP: Why is predicting these changes so difficult?

JS: Well for one thing we don’t really know what scenario we’ll be looking at in a few years. I’m pretty pessimistic given events of the last few years that we’re going to have anything but an aggressive carbon emissions scenario. I think it’s going to depend upon the species. We’re going to have to help out. I think many species are not going to be able to evolve fast enough in place. So we’ll have to intervene with assisted gene flow, but how do we choose which ones we want to assist?

SP: Can you take me through the concept of assisted gene flow?

JS: So we want to find out which climate a species likes and where’s that climate going to be in the future. There’s some cases where in fact the species range in the future will be almost non-overlapping with the range it’s in now. So how’s it going to get there? After the last glacial maximum, when the glaciers retreated the trees were able to keep up, but that was happening in orders of magnitudes slower than the rate that the climate is changing now.

The idea is for crucial keystone species, species that are important to the ecosystem, that we should be helping them to move. And that’s very controversial. Because are you essentially engineering species invasions, with limited knowledge of what that will do to the community that is already there. Assisted migration isn’t that aggressive. The idea is that within an existing species range, you move genotypes around to maximise the genetic variation to cope with the climate that’s coming. So in general that would be making sure you’re saving all the genotypes you can from that southernmost edge before they go extinct. And then moving them polewards to provide genetic material for the new climate.

To read up on the work that Johanna’s lab does, click here.

A Snapshot of Ireland’s Ecological Landscape

Last week, the NTNU University Museum’s Department of Natural History was benevolent enough to send its staff on a four day journey around Ireland. My previous experiences with Ireland have been two somewhat ill-fated trips on New Year’s Eve 2008 and St. Patrick’s Day 2012, so I was eager to see Ireland’s greener side. In an attempt to spruik some of the more interesting parts of the trip, I’ve broken it down below.

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Matt von Konrat: Harnessing Community Science

Matt von Konrat has been using community science at the Chicago Field Museum to generate data that it would have taken years for a single research team to produce, and engaging the public at the same time

Public engagement is something I’ve spoken about at length with the scientists I’ve been fortunate enough to talk to. However communicating better with the public is one thing; actively getting them involved in the scientific process is another. Matt von Konrat, of the Chicago Field Museum, has led an ambitious project which has successfully involved thousands of Americans from all walks of life in the scientific gathering of data. The result? Millions of specimens quantified, and thousands of people left with a better understanding of science.

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Episode 2: The Ents

This week we look at the Ents, of the little known cult comedy Lord of the Rings. Adam really just nerds the fuck out (we get it you read), Dave reveals he doesn’t believe in new Zealand and Sam rediscovers the art of the pun.

Movie History – 0.04.55
Movie Any Good? – 0.16.38
Ent Physiology – 0.21.06
Ent Ecology – 1.01.02
Treebeard vs. Christopher Lee – 1.24.30

Listen to the full episode below. For a more detailed breakdown, head over to Cinematica Animalia.


The Common Ragweed

The common ragweed, set to become a nightmare for hayfever sufferers

Guest post by Vanessa Bieker

In this series, we’ve already learnt about the impacts of alien trees and garden plants in Norway, but others are invading too, including some that are easier to overlook. And some of them can not only out-compete native species, but also pose health problems for humans. In today’s guest post by Vanessa Bieker, we look at Ambrosia artemisiifolia (common ragweed), which produces highly allergenic pollen and is one of the main causes of hay fever.

What is it?

Common ragweed is an annual wind pollinating weed that comes from North America, and was introduced to Europe in the late 19th century. Today it is found on every continent except Antarctica. It is established in South Europe (etc. France, Italy, Hungary) where the climate is more similar to that in its native range, but it is spreading further north. By 1996 it had reached Sweden and it has now spread to Norway, although it seems that it is not able to reproduce here yet. This is likely to change in the near future due to a warming climate and its ability to adapt. The plant dies with the onset of frost, but seeds can remain viable in soil for at least 40 years. Common ragweed normally germinates in April and grows rapidly. It can therefore out-compete other plants. Fully grown plants can be between 30 cm and 2 m high. A single plant contains both male and female flowers and is able to self-fertilize. Thus even a single plant can give rise to a whole new population. The plants tolerate damage quite well, they have the capacity to regrow and produce flowers even after mowing.

How did it get here?

A. artemisiifolia is usually found in disturbed habitats such as abandoned fields, along roadsides, at construction sites or in private gardens. The ragweed can be spread in many ways, from harvesting or mowing machines, to the spread of compost that contains ragweed plants.  The seeds seem to be rather heat tolerant and can survive composting. As the seeds can float, dispersal through water streams is also possible. The main vector into new ranges is probably from contaminated seeds imported from North America, especially sunflower and bird seeds. About 70 % of birdseed mixtures are contaminated with ragweed seeds, which are often able to germinate.

What does it do?

Bad news for people already suffering from hay fever: due to the late flowering of ragweed (August – September), the pollen season expands. Because the size of the pollen is extremely small, it can be carried by wind several hundreds of kilometers. And a single plant can produce quite a lot of pollen (up to 2.5 billion grains per plant per day). So it’s best to get rid of the plant before it starts to flower. This will also help preventing it from spreading further. If you want to get rid of ragweed in your garden, it’s best to wear gloves as it can also sometimes cause dermatitis even if you’re not suffering from hay fever.

But there is not only the problem for people with hay fever. Ragweed is also a huge pest in agriculture as it causes immense yield losses (up to 30 % in soybeans).


This is legitimately the only decent free-to-use photo I could find when I googled hayfever. I wish I looked this good when I sneezed, and not like you’re alcoholic uncle with mussels for eyes. (Image Credit: Public Domain Pictures)

What to do about it?

Common ragweed is still pretty rare in Norway, but actions against it should already take place before it manages to become established here. Once an alien species is established and widespread, eradication can be very difficult (or impossible) and rather expensive. Ragweed for example can build up a seed bank relatively fast. Most of the seeds produced in one year will germinate in the following year, but some seeds remain in viable in the soil. So if no seeds are produced in one year (because the season was too short or the plants were removed before flowering), those remaining seeds from previous years can germinate in upcoming years and thus keep the population alive.

A good way to get rid of ragweed is by uprooting the plants. As they have a high ability to regrow, those plants should be stored without contact to soil. It’s best to do it before plants start to flower to prevent pollen production and reproduction, as contact with ragweed can lead to skin irritation, gloves should be used.

If you suspect that you have found common ragweed, you can use the following webpage to help you confirm it:


If you would like to know more about common ragweed, we invite you to read the following articles:



Alien Trees & Filling the Knowledge Gap

recent report jointly published by WWF, Sabima, Friends of the Earth Norway and the Norwegian Botanical Society showed that alien tree species are one of the largest threats to native tree species, even inside protected areas. The news even reached Norwegian news outlet NRK. But why are alien trees a problem? Isn’t a tree, well, just a tree? As guest blogger Tanja Petersen explains, not quite.

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