The Trees of Gov­er­nors Island: Sur­vey­ing Our Diverse Canopy

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The young trees of Hammock Grove in the foreground, with the older trees of the North Island surrounding Liggett Hall in the background.

Guest post by Mal­colm Gore, Arborist at the Trust for Gov­er­nors Island

In the Win­ter and Spring of 2022, the Trust for Gov­er­nors Island con­duct­ed a sur­vey of all trees on Gov­er­nors Island to bet­ter under­stand the diver­si­ty, health, and longevi­ty of our unique urban for­est. The Trust received a grant from the New York State Depart­ment of Envi­ron­men­tal Con­ser­va­tion in 2021 to com­plete this sur­vey, and con­tract­ed Dav­ey Resource Group, a nation­al­ly respect­ed tree com­pa­ny, to con­duct the sur­vey and cre­ate a Com­mu­ni­ty For­est Man­age­ment Plan for this cru­cial canopy resource sit­u­at­ed in the mid­dle of New York Harbor. 

Why sur­vey our trees? It’s crit­i­cal that we have the full pic­ture of the Island’s tree canopy to make sure we are the best stew­ards we can be, ensur­ing our trees sur­vive — and thrive — for years to come. Gov­er­nors Island is home to almost 3,500 trees (3,496 to be exact) com­pris­ing 123 dif­fer­ent species. Of these trees, 97% are in either fair, good, or excel­lent con­di­tion — mean­ing they will con­tin­ue to pro­vide count­less ben­e­fits to the many human and non-human vis­i­tors of Gov­er­nors Island for years to come. Before div­ing into the spe­cif­ic ben­e­fits pro­vid­ed by our arbo­re­al friends, let’s take a look at the diver­si­ty of this island forest. 

Lon­don Plane Trees, with their dis­tinc­tive white bark and arch­ing branch­es, are the most plen­ti­ful tree on the Island as the 422 indi­vid­u­als rep­re­sent 12% of the total tree pop­u­la­tion on Gov­er­nors Island. They also account for a whop­ping 54% of the total leaf cov­er on the island, since most of them are mature trees that were plant­ed when Robert Moses was NYC Parks Com­mis­sion­er (while we aren’t sure the extent to which he had a say in the trees plant­ed on Gov­er­nors Island, Lon­don Plane Trees sprung up in huge num­bers across the city dur­ing this time peri­od— it seems they were his favorite tree). Hav­ing a sin­gle tree take up 12% of the canopy does come with some risk — if a new dis­ease that affect­ed Lon­don Plane Trees were to sweep through New York, Gov­er­nors Island would lose a lot of its canopy. This dis­ease risk is pre­cise­ly why the Trust is active­ly plant­i­ng many dif­fer­ent native tree species that will make our urban for­est more resilient. 

Com­ing in sec­ond are Swamp White Oaks, with 202 indi­vid­u­als that com­prise 6% of the total, fol­lowed by 150 of both North­ern Red Oaks and Riv­er Birch­es. Round­ing out the top five are the 120 Sweet­gums that call the Island home. These native tree species are vital­ly impor­tant to bird and insect pop­u­la­tions, as many types of cater­pil­lars (AKA baby bird food) feed on their leaves in the spring and summer. 

Addi­tion­al­ly, the major­i­ty of these trees are young and, as they grow and mature, will pro­vide more habi­tat and food for the pletho­ra of fau­na that vis­it the Island every year. 

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Photo by Sarma Ozols

Bio­di­ver­si­ty isn’t the only impor­tant thing to con­sid­er when main­tain­ing a healthy tree canopy; the age diver­si­ty of the Island’s tree pop­u­la­tion is also impor­tant. Mature trees pro­vide more habi­tat and shade, but are also riski­er giv­en their greater bulk and sur­face area to catch wind­storms. The below chart rep­re­sents the rel­a­tive age of Gov­er­nors Island’s trees as com­pared to the ide­al to sus­tain a healthy forest.

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Age breakdown of Governors Island's trees as compared to the ideal, compiled by Davey Resource Group, Inc.

As you can see, Gov­er­nors Island’s tree canopy con­tains near­ly dou­ble the amount of rec­om­mend­ed young trees — this is large­ly due to all of the trees plant­ed with­in the last five years in the Island’s award-win­ning park space. With prop­er care and time, these young trees should devel­op into estab­lished ones as soon as 2024, and this new urban for­est will become more robust and self-sufficient. 

Cur­rent­ly, only about 91 acres of Gov­er­nors Island’s 172 acres are con­sid­ered shad­ed, and the vast major­i­ty of that is in the Island’s His­toric Dis­trict under those 422 Lon­don Plane Trees. As the young oaks, sweet­gums, and birch­es grow and mature on the South Island, more of the Island will expe­ri­ence the cool­ing ben­e­fits of tree shade, thus ensur­ing that the island becomes a place to escape the city heat in upcom­ing summers. 

Besides shade, what oth­er ben­e­fits do these 3,500 trees pro­vide for New York­ers? For one, trees are experts at remov­ing pol­lu­tion from the air. The Island’s for­est removes 1,160 pounds of air pol­lu­tants annu­al­ly, improv­ing the air qual­i­ty and lung health of peo­ple in the sur­round­ing area. The more trees in a giv­en area, the bet­ter the air qual­i­ty which trans­lates to reduced rates of asth­ma and stress, and improved cog­ni­tion.

Trees also ben­e­fit the health of the plan­et by stor­ing car­bon. The trees of Gov­er­nors Island con­tain approx­i­mate­ly 1,245 tons of stored car­bon, and every year they cap­ture and sequester an addi­tion­al 22 tons. Mature trees store more car­bon that younger ones, sim­ply because they have more sur­face area and larg­er root sys­tems. Every year, trees grow a dense net­work of small feed­er roots, made of car­bon, that will die and be turned into organ­ic mat­ter in the late fall. The larg­er the tree, the more feed­er roots they grow each year, and the more car­bon they sequester underground. 

This is just one rea­son why the Trust is ded­i­cat­ed to main­tain­ing the health and longevi­ty of as many mature trees as pos­si­ble, and is tak­ing steps to reduce the upper canopy of at-risk trees so their roots sys­tems can con­tin­ue to cap­ture and store car­bon for many years to come. 

In addi­tion to stor­ing car­bon, trees can help mit­i­gate the effects of cli­mate change by reduc­ing storm dam­age and runoff. Tree roots act as giant sponges, soak­ing up vast quan­ti­ties of water that could quick­ly turn into tox­ic runoff, and the canopy inter­cepts del­uges of rain that would oth­er­wise hit the ground with force and cause com­paction or flash floods. On Gov­er­nors Island, the canopy pre­vents up to 378,000 gal­lons of runoff annu­al­ly, improv­ing the soil of our park space and pre­vent­ing pol­lu­tants from con­t­a­m­i­nat­ing New York Harbor.

All the data result­ing from this sur­vey is incred­i­bly valu­able to the Trust for Gov­er­nors Island, as it will help inform deci­sions on tree plant­i­ng, park main­te­nance, con­struc­tion projects, and pro­gram­ming events. The 3,500 trees on Gov­er­nors Island are a vital resource to the peo­ple of New York, and the Trust is com­mit­ted to ensur­ing that this cru­cial urban for­est remains healthy and resilient for many years to come. To learn more about urban forests and trees, come to Gov­er­nors Island on Octo­ber 15 for our City of For­est Day event — includ­ing a spe­cial vol­un­teer activ­i­ty and a tree walk­ing tour around the Island. Click here to learn more and register.