I study how climate change will effect trees and forests. AMA!

How will climate change effect trees and forests?

Chapeau, you were quicker than me.

ups, typo. Sorry for that! :)

How fucked are we?

eheh that is a question, I think, we honestly don't have answer yet. My feelings? Quite a bit, especially because there is not enough interest in using strategies that can successfully mitigate not only climate change, but also loss of genetic diversity, global spread of pathogens, deforestation and desertification. The problem is that we may start seeing the effects when is too late to do something about it.

do you expect some form of homeostasis to take effect naturally? As the planet gets hotter more plant life will flourish? possibly including the artic regions being able to sustain more plants, would the planet start to self correct. Obviously human habits will need to get changed as well to make a large impact. Just curious what your thoughts are on the planet self correcting.

That's a wonderful question! Plants show strong plasticity, so it could be the case that some of them would figure a way to take advantage of changes in climate to thrive (generally at the expenses of other plants). For example, for a while people have been exploring if in case of higher concentration of CO2 plants would increase photosynthesis and hence carbon storage in their biomass. Unfortunately I suspect that it won't be that simple (or quick); for example, even if temperature is rising, precipitations may even decrease, which would create an even harder environment to colonize. Your example of the arctic, actually, is a good one. In the past, during the glaciations, several trees species migrated south, and then back north after glaciations ended. The problem in this case is time. Trees grow fairly slowly, and a colonization of the arctic could take centuries, and we are potentially facing a crisis happening in a few years.

What is the difference between effect and affect?

this is a beautiful question, and I hope I can answer it decently :) From ecophisiological studies or data-driven models, we can infer what is the "marginal" effect of climate on trees distribution (or foliar chemical compounds). In short we can get a hint of what is the relationship between temperature and the probability of having maples in a particular forest, given that maples could potentially be in the area. To address how future climate will affect future distributions of species requires analyze those relationships in presence of new climates. Those new climates can be future projections predicted by physical models that reproduce some expected future scenarios.

In some countries, like Russia, global warning is seen largely as a benefit, since vast amounts of previously inhospitable land will open up for farming and other forms of exploitation.

What are your thoughts on this, and who are the biggest "winners" in these situations?

As somebody was mentioning before, when we talk about Russia is even more complicated, because there are several sources of uncertainty that we don't know much about just yet. I am thinking of the potential effects related to the loss of permafrost, uncertainty in the effects of a warmer climate on evergreen forests that could be stressed by the new environmental conditions. Or even the spread of new pests because of the warmer weather, that could impact large amount of forests. It is possible that larger areas could become warmer, but changes in precipitation patterns or extreme climatic events could undermine these advantages. In short I don't know if there will be winners who don't have to pay a fair price too

Professor Neal Peart says that the Maples want more sunlight and the Oaks are ignoring their pleas. Is there any truth to this?

Maples want more sunlight and the Oaks are ignoring their pleas very cool song indeed! Fun thing is that there are evidences of its lyrics to be true :D For example, it seems that maples experienced changes in recruitment dynamics in the last 40ish years because of changes in phenology induced by climate. In short, if climate gets warmer, oaks may start making leaves sooner, not giving a chance to young maples to store energy, which end up starving. Who said that trees are nice creatures? :)

Hi Sergio! This is very timely as my friends and I were pondering a relevant question just this weekend. I live in Wilmington NC. We're traditionally defined as "sub-tropical" but even laypeople over the last few years have noticed a warming, precipitation and humidity change. Last year was the wettist on record even without the 30+ inches of tropical storm rain we received. At what point will these factors begin substantively effecting the flora and will we begin to see tree species "migrating" northward to replace the native varieties? Have we already reached that point?

This is a wonderful question, and I hope I can answer it properly! :) I don't know exactly the case of your town, but I think it would take a longer time for your area to be considered shifting from an ecoregion to another. Hence, I don't think you are already at the point of a major shift in the flora composition. Some species, especially herbs and annual plants are more likely to colonize your environment faster, for their life cycle is shorter, and they disseminate further. For trees is slower, since some take years to become sexually mature, some disseminate not very far, etc. From my experience, generally things get dramatically faster if the new climate facilitate the diffusion of pests and pathogens that could attack and kill some species quite fast.

Hi, could you explain us how things like deforestation increases the global warming factor?

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Thanks for doing an AmA

Hi! thank you for asking! Despite deforestation is not my main focus theme, what I can tell you is that there are evidences and simulation studies suggesting that large scale deforestation have strong impacts on global warming. That is not only because there are less trees to absorb CO2, but also because of the reduction in the ability of storing water into the soil, transporting it back into the atmosphere, reflect part of the radiation coming from the sun. For example there are studies that suggest that deforestation in the amazon may affect water circulation and storm frequency in Asia

Thanks for your AMA!

Have you seen the recent study that planting trees could help slow down and potentially reverse some of the effects of climate change? Given your studies do you think this to be a viable possibility?

Hi! Yeah, we were discussing about that paper with a friend, and despite it being a good solution, I think they are overstating their numbers in terms of potential of Carbon mitigation of about 2x. That said, I think it is a wonderful study even just in spotting suitable ecosystems to address optimized conservation/reforestation plans

How many trees need to be planted to offset current carbon emissions world wide?

My quick answer is "too many": replanting trees may not be enough already. There is a paper published in science a week ago that suggests it is possible to plant 4.4 billion ha globally if we optimize forests cover, and that would cut CO2 in atmosphere of 25%. However, the authors estimations of carbon stock per tree are double than calculated by other meta-analyses: so we would need around 9 billion hectares to reach that goal by replanting forests.

So.. 10% of the US?

US is approx 982 Billion Hectares.

I know, doesn't sound that huge of a number, but you'd have to subtract all semi/desert areas, developed and urban areas, and what is used for pasture and agriculture, because they may not be available for planting new trees. From what they suggest in their paper, that's kind of the maximum tree restoration potential we can get. If you are interested, here is a link to their study: https://science.sciencemag.org/content/365/6448/76

Is that what would (gradually) solve carbon issues for the whole planet though? not just the US?

I think it is definitely a fundamental component, but I think it will be needed to pair it to a more and more sustainable strategy of growth, and in general a more and more eco-friendly development

How will climate change affect the forests in Siberia?

I haven't worked on Siberia or taiga forests, hence I may not be the best person to ask to. My understanding is that they could increase in productivity both because of warming, but especially because of colonization of the colder environments where now forest can't grow. On the other hand, the process may be slow, and am not sure about how much time will it take for species with higher productivity to colonize it. Moreover, if those areas become more accessible to human activity (e.g. agriculture), probably there will be even less forests.

Are there going to be more forests (CO2 fertilization), or will the forests die and burn and so on?

Hard to tell, especially at large scale. In some areas there may become better environment for forests, in other because of changes in precipitations or spread of pathogens, conditions may be worse. Plus, forest cover mainly depends in intensity of deforestation. My guess is that the CO2 enrichment won't be as impactful as we hoped, forest will still be around, but tree species distributions and co-occurrence may change significantly

How will the increase in carbon dioxide affect the growth of trees?

There have been a number of studies in the last couple of decades that focused on that question. You can search for "FACE" experiments to find some, for example. Good news is that higher CO2 should increase the potential for photosynthesis, bad news is that CO2 is not the only thing involved: plants need Nitrogen to make the proteins for photosynthesis (Rubisco) and Phosphorus to transform light in energy currency. Even if CO2 is higher, if there are not enough leaf nutrients, trees may not experience much increase in carbon storage.

Do you ever do any study on site or it is all data and data banks collected by field operatives?

Hi! in my case I use almost only data collected by field operatives and scientists. Mainly for two reasons: the former being the volume of data I need to explore dynamics across scales from local forests to continent. I have to deal with something like 15 million trees collected throughout the US, plus fancy airborne images and radar that would be too expensive to get myself. The other reason is that these data are openly available, and hence anybody will be able to download them, apply and explore my packages, and reproduce themselves my results. I generally use a combination of NEON data, FIA, BIEN, NASA and Fluxnet. Let me know if you are interested in some links or more information :)

Can you link me to resources for this data and the images?

Absolutely! NEON: https://www.neonscience.org they provide both data taken from the field, with GPS position of some of the trees, and a bunch of other awesome ecological data FIA: is the forest inventory and analysis, with not reliable GPS positions, but awesome data for tree species distribution across the continent: https://www.fia.fs.fed.us

Cool data from NASA belong to the G-LiHT program: https://gliht.gsfc.nasa.gov they have hyperspectral and lidar data scattered across the US

Do you plan to travel after you get your doctorate, so you can see where your data came from?

Also, so far, how is the data coming together? (just a brief “looks like we are going to burn to death in the next 50 million years” or “we got this” would be fine)

I wish! I'll most likely have to go back to my country right away. I had the luck of exploring some of these sites, both in Europe and here in US, and the folks who collect them are quite awesome! As to my studies, for what I've been seeing I don't expect a "global desertification" but changes in species distribution, definitively. What I've found, so far, is that climate can influence directly the productivity of a forest, but the gene pool of that forest is as important (or sometimes even more important) than climate itself. If we lose evergreens from a forest, for example, the entire ecosystem would shift completely and potentially not reversibly. I guess my answer is that if green-life didn't disappeared in the past it won't in the future, but will definitively change shape and form, and with it the services it provides.

That makes sense. Does your study take into account man-made structures and how they have or will potentially affect the ecosystem? Such as the Great Wall of China or the Not-so-great-wall of Trump? Or the tree buildings of Singapore? Adding green spaces to cities... and whether those green spaces should be native plants and trees or imports and how that might affect things?

Unfortunately I don't have enough clear data for including the potential impacts of man-made structures or green spaces in cities in the projects I am currently working on. I think (and this is a personal opinion) that green spaces to cities is a wonderful idea, as like as investing in technologies to phytoremediation (plant trees that can purify waste or sea waters in semi-desertic urban areas. However I would be cautious on using non local species, since they could potentially cause other kind of troubles (such us introduction of pathogens, or species invasions)

Addressing these fundamental questions is challenging, and requires fusing multiple very different datasets.

Could you elaborate on what datasets you fuse together? And what are the key data points that your ML models use to learn about carbon mitigation and ecological health?

Awesome question: glad you asked! :) the datasets I am currently focusing on are mainly the Forest Inventory Analysis (FIA), NEON vegetation structure, NEON Airborne Observatory Platform, and Daymet. The FIA is a dataset with around 15M entries, and has samples of forest patches on a grid with nodes every few km2 across the entire US. NEON can be used to derive around 20Million trees in a continues space of 200km2, but there are only few sites across the continent. Daymet has historical climate data per 1km2 resolution. Depending on what information I need from the remote sensing data, we use a combination of Convolutional Neural Nets, gradient boosting and random forests. To get the effects of climate on joint traits distribution I am using multilevel multivariate regressions with the phylogenetic relationship among tree species as random effect.

Here in Maine I have heard how the lack of very cold winters allows the hemlock wooley adelgid population to grow endangering the eastern hemlock trees. Are there other bug populations that behave similarly?

Unfortunately there are several examples that are similar to the hemlock wooden adelgid. An example that people use often in the US is the Mountain pine beetle, that from south could spread into parts of sub-Arctic Canada by 2080 (https://insideclimatenews.org/news/28082017/southern-pine-beetles-spreading-climate-change-northern-canada-new-jersey-maine)

Do you think young people should be taught about forest conservation and how using managed forests (and replanting) is important to CO2 sequestration and reduction? If so, how would you suggest it be included into school curriculum?

My personal opinion is that Carbon mitigation should be only a marginal topic when talking about the ecological and social importance of forest conservation and management. I feel young people may be more interested into the value of landscape conservation, the value on being able to see wildlife, realize they are fundamental for clearwater, and so on. I would probably include an ecology class that is part in school, but more important partly hiking in the nature.

What perspectives are necessary from other fields (chemistry, physics, bio, engineering, etc.) would you say are the most influential in helping solve certain problems?

In my opinion a mix of all; from engineering we need methods and technology for monitoring and get better information (machine learning), new materials, solutions to reduce pollution and emissions; we need chemistry and physics to get more and more reliable estimation of nutrients cycles and atmosphere circulation. I think ecology is the linking field among them, for it embeds information about the difference between climatic potential and effective possible achievable structure of present and future forests

What GCMs do you use in your research?

Currently I am not using a GCM, despite I've been playing around with ED2, CLM and co-developed 3D-CMCC-FEM. The reason why am not using them right now is because I am more interested in understanding directly what's the relationship between those chemicals that influence photosynthesis, growth and respiration and species distribution, using a more data intensive approach

Specifically in regards to Florida... Realistically(I guess what I mean is going by the most widely accepted models/predictions), what is probably going to happen to the state in the next 50 years?

Despite climate change predictions are far from exact forecasts, the scenario could be of up to 4 feet sea level rise, affecting more than 100 towns in Florida. It is not clear yet if hurricanes are going to increase in frequency/intensity, because current data may still be insufficient (seems they are increasing, but could also be that's because we got better in identifying them thanks to satellites). A study on Nature suggests that Florida could be damaged by sea level rise for 0.6 to 1.3% of state gross domestic product (GDP) (https://science.sciencemag.org/content/356/6345/1362). Temperatures could potentially rise up to 9F, with likely increase of "extremely heat" days (maximum temperatures of 95 degrees or more). As for tree species, here is a resource that can give you a hint of which species to expect to expand, and which instead could likely disappear (https://www.geobabble.org/ForeCASTS/atlas.html).

Hey Sergio. I’ve been a climate change activist for quite a while now and I’m just getting more and more depressed about the situation we find ourselves in. Added to that, my Wife just recently found out she’s pregnant but I’m not sure I want to bring a baby in to a world that’s essentially dying due to man made problems. She even got this priest to come round and talk to me the other day but nothing is getting me out of this funk.

Can the situation we find ourselves be resolved? What drastic measures do you believe we need to take in order to save this planet?

I honestly don't think we are on the edge of the Armageddon, and I think that if I'd like to have somebody to give new eyes to our world, that's definitively somebody who is actively involved in making it a better place. I think there are evidences that we are going to face an ecological crisis? I think so, but that's why we are studying how to face and mitigate it. For example there are several studies coming out in the last few years that actively use satellites to spot where vegetation in need may be, forecasting of potential species distributions, where to plant trees, fire ignition and spread, automatic recognition of animal and plant presence from cheap cameras. All this to facilitate plants and animal conservation, production of fresh water, and so on.

I am a teacher, what direct things should classrooms be doing to combats climate change besides simple tag lines like “recycle, use less, and plant more!”?

My personal opinion is that one of the best ways to show students the value of nature is by organizing hiking classes.

What datasets and analysis tools do you use for species classification? Do you work in a 30-meter raster context?

I've spent the last 10 years or so trying to get progressively better ecological data to inform the transportation/land use planning process for my metropolitan area. We've had some success combining multiple dates of imagery (leaf-on and leaf-off, color and near-infrared, etc) with DEM/DSM and other data to classify natural communities and translate those community types to ecological significance values. We ended up with a process that uses eCognition to delineate image objects (vector polygons) instead of rasters.

I am using mainly a combination of LiDAR and Hyperspectral from NEON data (and possibly, in the nearest future, from NASA G-LiHT). Those data are openly available, and have DTM/DSM at 1m2, full radiation reflectance from 350 to 2500nm at 1m2, and RGB data at 0.25m2 resolution. We are using the RGB to build a retina-CNN and do tree detection, then we use LiDAR based approach to better determine the boundaries of each crown. We think the RGB + liar method is perfect for doing tree detection/delineation, especially in urban areas (the biggest challenge, to me, is dealing with closed multi strata canopies, that induce over/under segmentation depending on the parameters chosen. you can easily use these methods if you can "talk" R or python (https://github.com/weecology/DeepForest or https://github.com/Jean-Romain/lidR)

Are we already screwed climate change wise? Or could sudden change save us?

I think we are not going to go extinct, but we need to actively change in habits and strategy to mitigate its effects on nature and on public health at local and global scale

How long have scientists been saying we will be fucked in just a few years? Serious question, as it seems like it has been quite a while. My entire adult life (I'm 46). I believe the scare tactics and other exclamatory words diminish their credibility. Additionally, the constant moving of the goalposts does the same thing, IMO. Also, how long have we feared the rising seas overtaking low lying cities like Venice, Miami, Houston, NYC, etc.? Why hasn't it happened, yet? Finally, won't higher concentrations of CO2 allow for more plant growth, since it is, in human terms, an "oxygen rich environment"?

While I am not a climate change denier, I believe many overstate the impact humans have on the earth, and minimize the earth's ability to heal itself. People who don't study history don't see that climate change has happened in the past, when there was much, much less human interference (I guess).

We easily forget that there are vast areas of our globe that are virtually untouched by humans. We constantly overstate our power and importance in this world because most of us live in cities where the 'change' is apparent.

Despite I can agree on the fact that we, as scientists, should discuss more about how uncertain we are about what to expect, I strongly disagree on the idea that no matter what, earth will heal itself. The example of past climate changes, for example, likely refer to either the glaciations, or the warming based on a warming in 5-8 C degrees in 10,000-20,000 years. In with cases, past climate changes happened in geological times, that is few thousand of years, which is not the current case. Moreover, it is embedded in openly available data: human activities are the main source of change in atmospheric levels of GhG, as they rised alongside temperature along with industrialization. On top of that, industrialization is now more spread across the globe, and mainly with highly polluting facilities in case of less strong economies that can't invest on latest technology to reduce their environmental impacts. Moreover, there are vast areas that were virtually untouched, that are getting dramatically deforested to make dams or agricultural lands and pastures (which turn into low fertility land few years later).

If you personally discovered positive proof that global warming is not happening, would you announce it to the world and have your entire life and career destroyed, or would you keep it to yourself?

I think that science is about learning and giving back what you learnt to the people. I would definitively submit the proof to the highest impactful journal and announce it to the world. For the same reason (sake of truth and transparency) I think it is fundamental that any piece of code, package, data and results coming from research should be delivered to the public, free and understandable to all.

From a layman's perspective, it seems like climate change would lead to the expansion of warm-weather climates like tropical rainforests and savannahs north and south from the equator towards the poles - is that in fact the case? Are we going to start seeing tropical rainforests and savannahs in the US creeping up into Florida, the Gulf Coast, and the Southwest from Central America and the Caribbean? Or will the deserts of northern Mexico effectively wall off the continental United States from existing rainforest ecosystems until new ones evolve, over a much longer (millions of years) timescale? Similarly, will tropical rainforests and savannahs reach up into formerly temperate areas of Eurasia, like contintental Europe or the Eurasian steppes? As a follow up, at the hottest latitudes right at the equator, will conditions become too extreme for even the current tropical ecosystems and species there?

Hey sorry for the late reply! I don't think we'll reach the point in which we'll se tropical forests in the US for many reasons. Tropical rainforest need high amount of sunlight, that is highest as closer you get to the equator, and lower as you get further. Moreover, they need very high humidity and daily precipitation. Geographical barriers like mountains, oceans or desert also, play a fundamental role in stopping tree species from creeping up, even the environmental conditions would have been optimal. At the equator, indeed, the situation could be worse. Some studies suggest that climate change and deforestation could affect the water balance, with reduced precipitations: in that case large portions of equatorial/tropical evergreen forests could evolve in ecosystems like savannah

If i want to plant a tree in the southeast united states, what species (if any) should i avoid?

depends on whether you want to plant a single tree or a forest. In both cases you should definitively avoid those species that are considered invasive (for example the tree of heaven), species that are not naturally present in the US and imported from another country, or that could spread the invasion of pathogens.

hello and thank you for your AMA.

can't stop thinking about melting permafrost and increasing levels of methane in the atmosphere. could you tell us a word or two on how this would impact flora worldwide?

permafrost is an interesting very uncertain variable in the whole Climate Change literature; methane as a climate altering potential that's 34 times stronger than Co2, and as the snow melts, the soil gets draker, hence warmer, hence more permafrost gets lost. As far as I know, we don't even know exactly what's the order of magnitude of emissions that could associated to its melting. As to the effects on trees/plant distribution, again, I can't really give you an educated answer, but my guess is that it would even more induce a shrink in evergreen species distribution at higher latitudes.

So are you going to predict a spatial distribution of various tree species? How are you going to collect data to feed your algorithm?

More or less what I am doing right now is to predict the spatial distribution of leaf chemical traits and across easter US and get the marginal effect of species identity, interaction among leaf traits, or climate on such distributions. I am using publicly available data; mainly FIA (https://www.fia.fs.fed.us), NEON (https://data.neonscience.org/static/browse.html), and tree of life (https://tree.opentreeoflife.org/opentree/argus/opentree10.4@ott93302)

What do you think about some of the new studies saying that climate change could be natural, by that meaning that, yes, climate is changing at an alarming rate, but it is less so due to man, and more so due to the natural cycle of the earth. Kind of how previous Ice Ages were not brought on my dinosaurs riding driving gas guzzling cars, but just a natural cycle. Here’s more info and a very well sourced article.

http://jennifermarohasy.com/2017/08/recent-warming-natural/?utm_source=share&utm_medium=ios_app

Sorry for the late reply . The study they are referring to in that blog post refers to a journal that has been discontinued, and scientifically I found it strange at least that it was submitted to a minor journal, given the high impact of their findings. Unfortunately I think that one of the reasons is that their study is not reproducible: there is no code available, nor input data, nor outputs. Their study supposedly uses curves collected from figures with rough estimates of past climates extracted from other papers. Their figures seem to have been manually made using spreadsheets. there is no way to replicate their findings. Moreover, their study is based on a model auto-trained on climate data (no physical knowledge included), in contrast with a wide literature of works based on both time-series data and/or physics.

Is there specific proof that climate change isnt fake through studying the trees/forest. Could you give an example.

There are several proofs about it, but I tend to say "there are proofs, but there is huge uncertainty on what's going to be the perceived effects to humans".

There is a "beautifully" paired increase in climate alternating gases, average temperatures and human emissions starting from the last few centuries.

That, combined with deforestation is affecting the distribution of forests in multiple ways.

One example is that a very little increase of temperatures allowed the spread of tree pathogens that are decimating such trees (like the red Beatle in Mediterranean palm trees in Europe).

What is the potential effect? Unhealthy (or widely cut) forests will not regulate water cycle, affecting, potentially, occurrence of big storms.

There's lots of proof here:

https://climate.nasa.gov/evidence/

I asked for proof through the trees specifically. Not evidence generally.

specifically to plants there is a specific example I like a lot: the heat wave and drought in Europe in 2003 that supposedly affected Carbon absorption from European forests, with a reduction of 0.5 PgC during that year. That is a specific case of effects of exceptional event, that we expect to experience more often than historically, as a consequence of climate change (https://www.nature.com/articles/nature03972).