I manage Restore Mass Ave, an environmental non profit that adds urban forest​ in Washington DC. Debthink is my personal site for posting about science policy, climate and other topics, with info about my books.


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Costa Rica postcard: New forests emerge from the trees 

Heredia Province, Costa Rica, March 2015

        I am tramping in dark woods, though it’s a sunny day here in Costa Rica. A man’s voice calls out “ocho,” “diez,” and a string of Spanish words. I know the speaker is Bernal, a local forester, though I can barely see him through the dense vines and the stems of young trees. He is calling measurements of red-marked trees to another forester, Jeanette. She stands braced on both feet to write his numbers on her clipboard.

        Not far away rises the fabled dense forest of Braulio Carrillo National Park, a jewel of the Central American cordillera and world attraction. From sea level the park ascends to 9,700 feet, its folded slopes covered in tropical forest and clouds.

        The ragged hillside we’re on is also typical of the region – and of Earth’s tropics. Here, ancient, primary forests were cut for human use; this slope became a rice farm. In 1986, a scientist, Bryan Finegan, arranged for this and three other plots to be let alone – no farming, no cattle-grazing – to record what Nature would do next. i

        What tree species filled in? Which ones lost out? Almost 20 years later, which trees are winning the ongoing ecological game known as  “forest succession?”  The numbers and species of trees and their width and height can answer many questions: How much carbon is stored in these trees? What ecosystem services are provided, such as water quality, erosion control and wildlife?

        Why did I come here? Because annual measurement of trees on this and eleven other one-hectare plots, ongoing for two decades, raises lively questions for tropical land management and global climate policy.ii

        This post is a heads-up for a longer piece I plan about cutting edge research on secondary tropical forests, a topic of growing importance in conservation policy.

        As Earth’s tropical rainforest continues to be destroyed at a horrendous rate, the area of former primary forest  land expands. In 2010 the FAO counted more than half of all forest land in the tropics as secondary forest.”iii   

      These expanding patches that humans have touched or ruined hold a tantalizing clue, because trees could grow there. Rapidly growing trees in young forests soak up more atmospheric carbon faster than old-forest land or urban areas.       

        So experts are asking:  If significant areas of available land were regrown as forest, could they absorb enough carbon dioxide to slow and maybe reverse the rise in atmospheric carbon dioxide concentrations?iv

       I met the trio of experienced tree-counters - Bernal Paniagua, Jeanette Paniagua and Enrique Salicette    at La Selva Biological Station, whose jungle campus is one of the world’s premier tropical research stations. We rode for about an hour on rutted clay roads, past rocky pastures laced with stands of trees. The trio pointed out trees and birds by their Latin and common names.  They stopped when Enrique spotted a new flower, so he could get out and pluck it, to add to La Selva’s tropical plant collection. 

       I was the guest of the Organization of Tropical Studies (OTS), a research organization in Costa Rica and the United States.v I had extraordinary help from the originator and lead scientist of this project, Robin L. Chazdon of the Department of Ecology and Evolutionary Biology at the University of Connecticut, though she was conducting research in Brazil at the time.  Besides a flood of scientific papers, her 2014 book Second Growth: The Promise of Tropical Forest Regeneration in an Age of Deforestationvi  has won wide new interest in the topic. 

       An exciting story is emerging at the one-hectare plot I visited, called Arrozal, and the others in Chazdon’s “Bosques” project. The new story is being written also by a wider long-term study of other recovering forests in Latin America known as NeoSelvas. One finding is that second growth forests in the early stage accumulate biomass, e.g. carbon, faster than predicted by standard models, but biomass varies dynamically over time.vii Thus is emerging the first detailed picture of these forest ecosystems through time. Still, scientists can’t say whether, they will resemble the original primary forest in another hundred plus-plus-plus years.

        Bernal, Enrique and Jeannette seem excited to be finding so many new and healthy trees. The day I visited, Jeanette added to the database 25 trees that had grown to the required girth of 5 centimeters. She recorded just three that had died.  (No one cycle of data-taking can tell the whole story; forest study plots have the equivalent of bad hair days.) 

        [Update: The standard method to compute once and future forest traits is chronosequencing; the data-taker records three traits of the trees on a plot, taking a snapshot of the present forest; then these traits are projected backward and forward in time, on the assumption that they stay the same.

        [But this model is called into question by a compilation of the most extensive long-term data set ever assembled for Neotropical (Latin American) forests. In the June 30 Proceedings of the National Academy of Sciences, Natalia Norden and co-authors including Chazdon modeled a wide range of traits of regenerating forest in seven plots in Brazil, Mexico, Nicaragua and Costa Rica, including the one at Arrozal.  

         They found that the standard method predicted just part of these forests’ traits. Which trees “succeeded” on a plot changed over time and from plot to plot.  A big factor turned out to be what grows outside of a plot.  Example: a regenerating forest plot is likely to grow more tree species sooner when old forest remnants are nearby.] viii

        Fieldwork has found a promising variety of tree species on the Arrozal plot, though it has been left to regrow for less than two decades. Chazdon said its species richness is helped by the embrace of Braulio Carillo park. And along the red rutted roads among the pastures here, I saw many patches of 75-foot old trees from which birds and other wildlife can spread seed.

        The hero of my longer article will be Nature regrowing itself. The supporting cast will be those who let this degraded land alone, for decades, for Nature to go to work. 

       One plot twist will be money. Many landowners in the tropics are tempted to sell or rent their poor-seeming land for cash crop production. From the highways near here, I noticed pineapple plantations, which are said to be expanding. 

     The more complete understanding of secondary forest traits could raise the present value of lands available for regrowth. National governments, such as Costa Rica’s, could grant higher benefits to owners who agreed to leave land entirely alone, or add trees strategically. Governments could use the recalculation of these forests’ carbon storage to help meet national and international climate goals.  

       The results of this research can help more local people hang on to, live with, and enjoy their forests. More, like Bernal, could learn to call birds, chatter with monkeys and get excited about flowers they haven’t seen before.

        If this work revalues tropical landscapes by shows it can store more carbon than previously thought, viii that would be worth a whoop from all of us.


Postcard from Stockholm: Nobel Surprises

Arriving in Stockholm at night in early December, I was struck by the rows of lights in the windows of the lovely old buildings. It was Advent season, so most windows had sets of white candles – traditional symbols of hope in mid-winter. Gleaming snowy streets wound like trails through dark town. Stockholm is laced with canals whose inky edges were fringed with brightly lit white boats.

Stockholm view from Grand Hotel. Photo: Mel MatthewsI came for the Nobel Prize awards. They are given by the Swedish king each December 10 to a handful of scientists and a literary figure, who thereby gain godlike status with colleagues and the world.

I had interviewed a few Nobel prizewinners during my science writing career. I grew up in a family of scientists. My grandfather was the Harvard astronomer Harlow Shapley, famous for his discovery that our solar system is not in the center of the galaxy. Most of Harlow’s extended family went into science.

So we were overjoyed to learn that one of Harlow’s sons, my uncle Lloyd S. Shapley, a well-known game theorist, was the co-winner of the 2012 Nobel Memorial prize in Economic Science.1 I was honored that uncle Lloyd included me in the accompanying group each winner is allowed. So – I came to Stockholm!

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New Tree Care blog

New Tree Care Blog has my posts (2011-current) about our work saving urban forest and working with embassies in Washington, DC. 


Warming will be worse, scientists warn, but Americans wait for the movie  

October 2009

Does new evidence of warming count as news?

This just  in.

Global warming is causing Earth’s systems to change faster than the most sobering predictions of a few years ago. Drastic changes that had been expected over long periods, such as the melting of Greenland’s glaciers, are occurring sooner.

And a respected model forecasts that, by 2100, average global temperature may rise by 4 °C (6.3° F) even if all nations carry out the cuts in carbon dioxide equivalent (CO2e) emissions they’ve pledged. A 4°C rise by 2100 would be twice the 2°C increase over preindustrial levels that world leaders declared in L’Aguila, Italy as the acceptable maximum.

These messages came through loud and clear at a press event

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