How Thoreau Can Give Us Insights into Today’s Climate

Transcript for Blue Hills A-Live video with Richard Primack

Watch the video on climate change with Richard Primack.


Judy: Today we’ll take a look at how Henry David Thoreau’s careful records of plant life can help us understand what’s going on in the Blue Hills. I’m Judy Lehrer Jacobs, the executive director of the Friends of the Blue Hills.


Richard: And I’m Richard Primack, professor of biology at Boston University.


Judy: And if you have noticed changes over the years that you have visited the Blue Hills please let us know in the comments, whether its different plants or number of visitors, trails, we would love to hear from you. This is Blue Hills A-Live, your weekly guide to the Blue Hills. We are grateful to our sponsor, Tom O’Neill of Success! Realty in Milton and if you’d like to know more about the Blue Hills you will want to download our free guide to the Blue Hills ,

There are over a thousand people who have downloaded the guide and we’ve gotten great feedback. We’d love to know your thoughts. Now we can start! Do want to start by just introducing yourself and letting us know what kind of research you have been involved in over the many years you’ve been at BU.


Richard: Well I’ve been at Boston University for 40 years. I’m a botanist specializing in plant ecology, plant identification, and plant conservation. Up until about 15 year’s ago I mostly worked on tropical rainforests in Southeast Asia but beginning 15 years ago or 16 years ago I became interested to see whether we could see any of the effects of global warming and climate change on the plants and animals of

Massachusetts and so we’ve been doing work all over the Boston area at place like Mount Auburn Cemetery, Middlesex Fells, but also the work which has really gotten a lot of attention is the work which we’ve been doing in Concord, Massachusetts. We found that in the 1850s Thoreau kept very detailed records of when plants were flowering, when trees were leafing out, and when birds were arriving in the spring and what we’ve been doing is comparing his observations from the 1850s with what’s happening in Concord today.


Judy: Why did you choose to explore what Thoreau’s records were and think about how to compare them to today?


Richard: We weren’t specifically looking for Thoreau’s records. We weren’t specifically looking for records in Concord, we were just trying to find any records of what happened in the past. Any records of what plants were growing in a place, where birds were visiting a certain place, when birds were arriving, just anything about what was happening in terms of the ecology and natural history of any place or any group of species in the Boston area and someone told us about Thoreau’s records. We had never known about these records. We had never heard about the records but as soon as we saw Thoreau’s unpublished tables from Concord, we knew that this was an amazing resource.


Judy: And how did you use the data?


Richard: Well we got these tables so we received the tables, his unpublished tables, from a Thoreau scholar and as soon as we looked at these tables, there were lists of when plants were first flowering in Concord from 1851 to 1850. It was just immediately obvious that what we needed to do was start gathering these observations ourselves so from 2004 up until the present time we’ve been going out every spring and making the same observations that Thoreau made in Concord and we’ve been doing that and probably in about in a couple of days I’ll start going out to Concord and making the same observations myself.


Judy: And what have you found?


Richard: We found that the wildflowers are flowering about 10 days earlier now than they did in Thoreau’s time that the trees are leafing out about 14 days earlier but the birds are only changing a little bit.

So some birds are coming a couple of days earlier and a lot of other birds, particularly tropical birds, like a lot of the Warblers and fly catchers are really not changing their arrival times at all. So species are responding to climate change but different groups of organisms are responding differently.


Judy: So what is that going to mean if the birds are coming later than the plants are flowering?


Richard: Well this is a very active area of research by ecologists. So what we started to do was to document that the different groups of species are responding to climate change differently and what we suspect is that this is going to create winners and losers but we don’t really know at this point which ones are going to be the winners and losers but there’s the possibility that people are considering that if birds are not responding to climate change then they might be arriving after a lot of the big peak of insect emergence in the spring and they won’t have enough insects to feed themselves or to feed their nestlings and this might be contributing to the population decline of a lot of birds in this region. We don’t know if this is really happening but it’s something we’re investigating. Or, similarly, if the trees are responding faster to climate change than the wildflowers it might be that the trees leaf out ever earlier and shade out a lot of the spring wildflowers that are merging before the trees in the spring. This is again something that we’re investigating very actively right now.


Judy: So is this a consistent trend or I imagine there was that one year that we had snow on the ground until late April and we had snow recently.


Richard: That’s right. So, New England has a famously variable climate so actually New England probably has the most variable climate of any temperate forest region in the world so we actually talked a lot about the weather, and we think a lot about the weather and it’s because it is so variable here and we have warm years and cold years. So this is the year of the northeasters. We’ve had all these big northeaster storms one after another. We had a somewhat warm February. Every year is different to New England. People like to talk about every year but what’s happening is that our years are consistently warmer than Thoreau’s years so we do have warmer years and cold years but on average our years are about four or five degrees Fahrenheit warmer than Thoreau’s years and this is enough to trigger the plants to flower earlier.


Judy: Does he have temperature data or do you just know that?


Richard: Thoreau didn’t have temperature data but the longest continuous weather records from anywhere in the country is Blue Hills Reservation, so it goes back to the late 19th century and then, through other records of farming communities or farming or farmers in this region, they’ve been able to extend the record back I think to the 1830s. So we have the longest weather records in the United States from Blue Hills and this is close enough to the weather of Concord that we really can take the weather records here and use this to determine how weather variation is affecting plant behavior.


Judy: We actually have a comment from Kaitlin Geagan, she says “Hi from Blue Hill observatory and

Science Center where we monitor the thaw and freeze of Houghton’s and Ponkapoag.

Are there similar records for Walden?”  So Kaitlin Geagan from the Blue Hill Observatory, which is great thanks for watching and commenting and she says that they have records on thawing and freezing, Is there anything comparable?


Richard: Well, it turns out that New England has probably the highest density of records of ponds freezing in the autumn and thawing in the spring probably of any region in the United States and all these records are again demonstrating that ponds are freezing later in the autumn than they did in the past and the ice is thinner probably, though we’re not sure about that, but they’re certainly thawing earlier in the spring and Thoreau made these kinds of observations from Walden Pond and in Thoreau’s time the Walden Pond thawed anywhere in the spring from mid-march through the middle of April and now the ponds tend to flow, tend to thaw in the spring from early March until late March. So the pond is thawing about two weeks earlier now than in Thoreau’s years and you can correlate that very strongly with the temperature, yet actually, in the Boston area from, Blue Hills Observatory right nearby here, in the months of January, February, and March, and if you remember back to 2010 and 2012 we had these astonishingly warm winters and in those winters the pond didn’t freeze until early January and then thawed at the end of January or early February.


Judy: Great. And if you have any questions on how the

Blue Hills are changing or how our forests are changing please let us know in the comments, and I’m assuming that the findings you’ve discovered in Concord relate to the Blue Hills.


Richard: That’s right. So at the Blue Hills, we really have the best records of anywhere not only in the New England area but actually the records that were gathered by Thoreau probably are the best in the United States in terms of the detail of the records and the long time span but these observations that we’ve made have been confirmed by other studies that we’ve done in the Boston area at places like Mount Auburn Cemetery or the Arnold Arboretum but also now people are starting to publish other studies like this, really from around the New England area and around the whole United States and all these studies are confirming that spring is happening earlier now than in the past, but we’ve also started to do, which is really interesting, is to extend these studies into the autumn season and we find that autumn is getting later so that birds are staying longer before they depart in the autumn for their over-wintering habitats to the south, that the trees are retaining their green leaves longer in the autumn than they did in the past. Butterflies are flying longer and again these are things that we have observed in specific places but a lot of these observations would include Blue Hills. It’s not that far from Concord and actually a lot of the butterfly records it turns out actually come from the Blue Hills because the Blue Hills, as we get along with the Middlesex Fells, are two of the favorite butterfly hunting grounds in Massachusetts.


Judy: So it sounds like some species will be able to or are adapting to this changing climate.



Right so some species are adapting and we find that the species which have the most flexible phenology, the most flexible timing are probably the species which are really going to do the best. Interestingly enough the species that are the most responsive to climate change are actually the non-native species often the invasive species so if you go out in a week or two you will actually find the Multiflora Rose and the Japanese Barbary, already starting to leaf out so they are the most responsive. They are the most responsive to climate change and that’s probably why they’re very successful at increasing in abundance in comparison with our native species but we find that there’s a range of species and some species are going to like this warmer weather and these extended growing seasons and other species aren’t going to like it and are going to decline in abundance.


Judy: So, to me, that’s a red flag, that the invasives are doing better than the natives and that might decrease the biodiversity here, the number of plants and species in the forest.


Richard: Right, that’s a concern. So climate change is probably going to change the college in these areas and you can see this in Blue Hills. I mean, Blue Hills is already a fairly dry area because of all the steep slopes and the rocky soils and the warmer temperatures which Blue Hills is going to be experiencing during the summer has already experienced and will continue to experience because of climate change will cause the area to become even drier and hotter in the summer and this will cause a lot of moisture loving species a lot of cold weather loving species to decline in abundance in the Blue Hills in coming decades. So the ecology will change and the species which really like warmer temperatures, like drier conditions will probably increase in abundance and in the short term it means that this will favor a lot of invasive species and also it will provide the setting for warm loving southern species to start arriving here and start increasing in abundance.


Judy: So if you have seen a particularly interesting plant that may or may not be around we would love to know what kind of plants you see in the Blue Hills. Do you want to start talking about maybe the causes of changes that you’ve been seeing? The changes in the timing of events or the kinds of species were seeing?


Richard: Right, so I mean there are changes which are happening and we’ve been carrying out these studies for 15 years in Concord and we see that when we have astonishingly warm years like we had in 2010 and 2012 that the plants respond by flowering so early that it’s beyond anything that we’ve seen in the past, of anything that Thoreau saw. We sometimes see that we have these very mild conditions in the winter so two years ago we had an extremely mild, extremely warm, December and there were actually many species that were flowering on Christmas Day in Concord and you can see that also in Blue Hills, things like dandelions or Japanese flowering quince, white clover was still flowering on Christmas Day which is something that was just unbelievable to see that. Last summer we had this severe drought and you can see these severe droughts… when we have severe drought conditions which are probably linked to climate change, it causes a lot of the trees to start losing their leaves, having their leaves change color, losing their leaves early. So this is something that Friends of the Blue Hills can actually see, so as you walk around Blue Hills you can see how these extreme climate change events are affecting the ecology of this area. It’s something that you can all see and it’s also something that the Friends of the Blue Hills can be involved in through something which is called the National Phenology Network. So then if the National phenology network is a citizen science network which encourages people to submit observations when they see plants flowering, when they see trees leafing out, when they see birds arriving, in the spring and then they can that’s called the National Phenology Network. You can look at it up online and you can contribute your observations to that and that helps scientist’s track the effects of climate change. Then for those who are bird watchers, the best resource of all is something which is called E-Bird. Which is run by Cornell University and that’s a service in which people can contribute their bird observations. It helps people to make a bird list and keep track of the birds they’ve seen but it also allows scientists to keep track of how climate change is affecting the arrival of birds in the spring and also the abundance of birds.


Judy: That’s great, that was one of my questions, what can people do… so you answered it.


Richard: Well that’s what people can do in terms of helping biologists but the larger question of what you can do about climate change, in mean what people can really do about climate change, which is a bigger question is to be involved in political organizations, whichever political party you belong to, whatever town you live in, to get involved in the political process, whether it’s at a state level and national level or even pressuring our government to get involved in international issues because climate change is something that we can deal with individually by using less fossil fuels, by driving less, by having more fuel-efficient cars, by keeping the temperature of our houses down, by eating less meat in our diet but it’s also something but we really need to be involved in the political process.


Judy: Kaitlin has another question and she could hear me the first time. She wants to know what the social, economical, and political reasons are why the general public should care? Do you have any input on that?


Richard: Well I think that there’s a lot of reasons why the public should care about climate change. I mean huge numbers of reasons why they should care about it. First well since we’re in Blue Hills, they should care about it because climate change is going to have a lot of negative impacts on a lot of the rare and endangered species that we love. So much so, actually just over the next few days the spotted salamanders are going to be migrating and if climate change continues, a lot of the rain that a lot of the vernal pools that the salamanders migrate are going to dry out and which is going to have negative impact on the spotted salamanders and many of the other amphibians and other animals that we love so much but it has real serious economic and public health consequences. So, in the Boston area, because of climate change we’re going to be having more heat waves during the summertime, more days in the 90s, and even above a hundred degrees, and when we have these extreme heat waves in places like Boston where people are not used to it and where all people don’t have air-conditioning it really increases the mortality of people who are sick and who are elderly. It really causes people to become sick and even die. Also one of the most dramatic effects of climate change is rising sea level. Boston has already experienced about nine inches of sea level rise over the last hundred years and we are predicted to get somewhere between two to six feet of sea level rise by the end of this century so on average about three feet of sea level is supposed to happen but within the next 80 years and if that happens that means every big northeaster and every hurricane that hits Boston at high tide, the water just going to go surging over the sea walls and is going to flood not only Gloucester and not only Quincy but downtown Boston and is going to cause tens of billions of dollars’ worth of damage. So climate change is something which is going to have huge economic impacts throughout Massachusetts but particularly on the city of Boston.

Judy: Kaitlin, did that answer your question? So we’re right near a Houghton’s pond, do you want to talk about some of the changes that will happen right here?


Richard: Kaitlin has already kind of tipped us off to the fact that that the Blue Hills Observatory has been monitoring the time of ice out and an ice thaw in Houghton’s Pond and Ponkapoag Bog and these are against some of the oldest records of pond freezing and thawing of any area in the United States so it’s a tremendous resource and the Blue Hills Observatory actually has mountains of extremely interesting data like this which they’ve already been using and which can be used in further studies so people continue to analyze this incredible treasure of resources but what this means here is that at Houghton’s pond is that the ecology of this area is changing, that a particular schedule of freezing and thawing that the animals in here are adapted to is changing. Which means it opens the opportunity for different species to come in here, for existing species to either do better or to die out, but it’s going to change the ecology of the pond. So for example the water snakes and the fish that live in this pond are used to a certain ecology and that’s changing and it represents an exciting opportunity for scientists to study these changes but also it means that that a lot of the things that have been living in this pond for decades or for centuries aren’t going to be able to live there anymore but there’s the possibility of seeing new things here so if you’re interested, in, say dragonflies, the dragonflies that people have seen in the past are going to be… some of them aren’t going to be here anymore but if you keep looking you’re going to see new species of dragonflies which is exciting.


Judy: So we don’t know how it’s going to all end


Richard: Well things are changing I mean even in the last 18 years that I’ve been looking at Concord, Massachusetts I’ve seen substantial changes in the flora of Concord so there were species that have been there for 150 years and are just now dying out and the last few individuals are remaining and I’ve seen new individuals coming in the people didn’t even see there ten years ago so it’s very exciting. I mean there are a lot of changes which are occurring some of the changes are bad but some of the changes are new and exciting.


Judy:  So what’s dying out?


Richard: Well one thing which is happening in Concord is a lot of the orchid species that used to be in Concord, used to be 21 species of orchids in Concord, and we’ve only seen seven or eight species and so that’s very disappointing. Orchids are very beautiful or trilliums which used to be very abundant in a lot of places in Concord. These large populations are declining and dying out so that is very disappointing but we’ve seen a lot of new species coming in a lot of the new species that we’re seeing coming in, the most the most noticeable of these are actually escaped ornamentals so plants that people planted in their gardens or were in public gardens or even in nurseries, commercial nurseries, are actually spreading from those areas and are spreading along roads or even into meadows or woodland edges so this is something which is which is very noticeable once you start looking for it.


Judy: And you’re not worried, it sounds like you’re not worried.


Richard: I am not worried because I am an optimistic person by nature. I find it very interesting and places like Blue Hills, I think it’s very interesting. Where it’s more frightening is in places like coastal areas of Massachusetts, so downtown Boston, around Boston University where I’m working, and again a lot of coastal communities, again, we recently had massive flooding in places like Gloucester and so in places like that people should be really frightened but I think that we are a very adaptable society, we’re a wealthy society, so we will adjust. See will make the adjustments, it’s much better if we make these adjustments before the disasters happen, but in some cases these disasters will happen and then we will rebuild. So that kind of thing will be happening but I tend for me a case which we have worries but it’s also very interesting.

It’s a time of change.

Judy: We have another question from one of the visiting students at the observatory, someone who is wondering if there are similar patterns of phonological changes occurring in different parts of the world?


Richard:  Yes, every place where people have looked for changes in phenology they find them.


Judy: Can you define phenology?


Richard:  So phenology is the timing of biological events. So in Europe there is a very extensive tradition of people recording when things are happening, probably the best records of all are the records of the grape harvest in France. The records, going back you know 500 or 600 years, showing that the grape harvest is happening earlier because the timing of grape harvest is very tied in with when the grapes flower in the spring. But there are lots of records in Europe. There are huge records now that people have started looking in Asia. The most extensive records in Asia are when the cherry blossoms flower in Japan. There were actually records going back over a thousand years in terms of when cherry blossoms are flowering in Japan and those records again showed that in the last hundred and fifty years the dates of Cherry Blossom flowering is getting earlier. So whenever people have looked, they found that there are a lot of records. The records are predominantly in the spring and these records, again, show that spring is happening earlier in Europe and North America and Asia and, again, in every place we look we wind up finding these records. There are huge amounts of these records in New England every time we go in looking for them. And also people are starting to find records in the autumn. So people didn’t look for records in the autumn as much but once people have started to look, once we’ve gone looking, we find that there are records in autumn and again they show that autumn is extending later in the year. People will start looking more for summer records and winter records, I predict, and they’ll again find that there’s a lot of interesting information there.



Judy: Do you have any more questions about climate change and the Blue Hills?


Richard: Nope.


Judy: Do you have anything more that you want to add?


Richard: Well the one thing I want to add is that we’ve also been working with the Friends of the Blue Hills to monitor sound in the Blue Hills. This is something we’ve already done some work here on and we’re planning to do more work in the future. So the first event which we had in the autumn, the Friends of the Blues Hills came out and supported our activities. About 20 people came out and they worked with myself in my graduate students and we did monitoring of sound very extensively in the reservation. We were interested in making maps of sound. Found, not surprisingly, that the sound was greatest along route 93 and a lot of the estate roads throughout the park. There was often very loud noise but as you started going about two or three hundred yards into the park the sound really dropped off quite dramatically.  This was a probably the main result that we got. We, interestingly, we didn’t monitor sound during the time that airplanes were flying overhead so it wasn’t a study of airplane noise but we find that the Friends of the Blue Hills are very interested in the sound of noise from airplanes landing and taking off from Logan Airport, so we’re planning to work with the Friends of the Blue Hills at another event, perhaps in June or in September, to record the frequency of airplane noise in the park throughout the park and also how loud it is in the park and this might help the Friends of the Blue Hills to document the serious problem and help to make the people of the government aware of this problem.


Judy: And we’ll let you know when we’ve scheduled it. So I wanted to thank you for watching, especially those folks at the Blue Hills Observatory. It was great to get your comments. You’re watching Blue

Hills A-Live, your weekly guide to the Blue Hills and we thank our sponsor Tom O’Neill of Success! Realty in Milton. If you haven’t already, you can download a free guide to the Blue Hills at and next Thursday we’ll be talking about vernal pools. See you next Thursday at noon.

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