Tag Archives: range

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.

Victory May Not Guarantee Survival in Species Conflicts

Spreading of the Australian yabby has led to decreases in other local species. But what happens when these species meet?
Spreading of the Australian yabby has led to decreases in other local species. But what happens when these species meet? (Image Credit: Daiju Azuma, CC BY-SA 2.5)
Insight into invasion: Interactions between a critically endangered and invasive cray fish (2018) Lopez et al., Austral Ecology, doi:10.1111/aec.12654

The Crux

When we talk about invasive species, often the first thing that pops into our minds are things like feral cats, wild pigs, vicious newcomers that wipe out species or transform vast areas. But often what we focus on less are species which arrive and simply outcompete the locals.

The yabby (Cherax destructor) is one such invader. An Australian species, it has been introduced to new waterways through the country and is now threatening other species, including the Falls Spiny Crayfish (Euastacus dharawalus) in eastern New South Wales, Australia. The introduction of the yabby has resulted in a decreasing habitat range for the crayfish, but what sort of mechanisms are causing this? This experiment aimed to document interactions between the two species.

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Gretta Pecl: Climate Change in Coastal Waters

Gretta Pecl, founder of the Redmap project, which aims to demonstrate tangible effects of climate change to Australia's fishing community

So often the effects of climate change are somewhat intangible to us; the weather may grow warmer, but it’s a slow and gradual process, which can seem entirely at odds with the alarm bells that things like the IPCC report seem to be constantly clanging. As such, demonstrating tangible environmental changes to a community whose livelihood may depend on such changes is a great weapon in the fight against the effects of a warming climate.

With this in mind, marine biologist Gretta Pecl founded the Range Extension Database and Mapping project, also known as Redmap. Redmap aggregates public sightings of fish to show shifts in the distributions of Australia’s marine species, including some that are crucial to our fishers. At the recent ASFB 2018 conference, I sat down with Gretta to talk about changes in marine species distributions, how they’ll affect Australia, and how they might help the public understand the effects of climate change.

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Changing with the Climate

An immature female blue-tailed damselfly (Ischnura elegans)

An immature female blue-tailed damselfly (Ischnura elegans) (Image Credit: Charles J Sharp [CC BY-SA 4.0])

Signatures of local adaptation along environmental gradients in a range-expanding damselfly (Ischnura elegans) (2018) Dudaniec et al., Molecular Ecology http://doi:10.1111/mec.14709

The Crux

Terrestrial organisms aren’t always stationary entities, they often move around the landscape searching for food, potential mates, or more ideal environments. Over time, these movements may introduce the species into new environments, as some change allows the species to expand their historical range.

An interesting aspect of this shifting of the species range is how the organisms at the edge of the distribution are maladapted to the novel environments, as most of the species will be adapted to conditions at the core of the species range. To overcome this, they must adapt to the new conditions. Successful adaptation is dependent on changes in gene frequencies away from the historical genotypes, with an increase in genes that promote survival in the new habitats. The authors in this study used molecular techniques to identify genes that new environments might select for.

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The Pacific Oyster

The Pacific oyster could make its way further north as the Arctic and sub-Arctic regions warm

Last Monday, I wrote about how climate change can facilitate the spread of non-native and invasive species. Today, we look at a species that whilst problematic now, could spread further throughout Norwegian waters as temperatures rise.

The last time we looked at an ocean-dweller in this series, we saw that while some species may not be great for ecosystems, they can provide an obvious benefit to other aspects of the region, in this case the fishing industry. The Pacific oyster (Crassostrea gigas) was also introduced intentionally for cultivation and is now on the verge of becoming a major problem in Norwegian waters.

What are they?

Because of its tolerance of most environments, the Pacific oyster has become the most widely cultivated oyster in the world, and thus one of the most widely distributed alien species in the world. Originating from the North-West Pacific, around Japan, it’s sometimes referred to as the Japanese oyster. There is some confusion regarding its taxonomy, with it also sometimes referred to as the Portuguese oyster, though it’s possible the two are separate species. They are large, jagged oysters, and occur in marine coastal waters.

How did they get here?

The oysters were imported into waters throughout Scandinavia and most of Northern Europe to replace dwindling stocks of native oysters at various points through the 20th century. Naturally, they eventually established wild populations as well, and are now abundant along Norway’s southern coast. Whilst they have taken over coastlines through much of Europe, their dislike of colder waters means that for now, their local populations are largely constrained to the south of Norway. But increases in temperature, which will occur at an accelerated rate in the Arctic and sub-Arctic, mean that the oyster could spread further north in the coming decades.


Whilst the Pacific oyster’s place in novel marine food webs is still not particularly well understood, these specific oysters place in their immediate food web is very obvious (Image Credit: Wikipedia Commons)

What do they do?

Much like the Red King Crab, they transform the local ecosystem into a homogenous mass. They can transform substrate from soft bottomed and muddy to filled with rocks and other oysters and mussels, also paving the way for other alien species, and lowering regional biodiversity by outcompeting and displacing local species. Interestingly though, presence of oysters can often improve water quality in the surrounding regions and heighten ecosystem productivity, though the position of the oyster in novel food webs is not particularly well understood. They also have negative effects for local human populations, making certain areas impossible to use for recreation, as they’re extremely sharp.

How do we stop them?

In other countries, attempts to eradicate wold populations by harvesting them have proved futile, and a 2005 study showed the oyster eradication would also cause substantial harm to the local ecosystem. Warming seas will mean the expansion of the oyster’s range, however this is likely to happen very slowly, so by focusing on the ranges edges it may be possible in the future to limit expansion.

For more information on the oyster, we recommend that you read the following articles:

Invasive Alien Species Fact Sheet – Crassostrea gigas by the Online Database of the North European and Baltic Network on Invasive Alien Species

Crassostrea gigas – Cultured Aquatic Species Information Program by the Fisheries and Aquaculture Department of the United Nations

Invasive Species and Climate Change

The next 50 years will see parts of the planet warm significantly. So how does this impact invasive species?

In this series, we’ve looked mostly at species that have been introduced at defined points in time. The Pink Salmon and the Red King Crab were introduced into Russian waters near Norway in the 50s, the Canada Goose was brought to Europe in the 30s, the Sitka Spruce in the late 1800s. But with the onset of climate change, warmer conditions in the Arctic and sub-Arctic mean that the doors will open for more gradual arrivals. So let’s look at how climate change will facilitate the arrival of these newcomers.

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