Friday, June 5, 2015

NYC waters- Randall's Island

Long Island Sound and the Atlantic Ocean are connected by what New Yorkers call the East River, which is actually a waterway called a strait, in this case having tidal flows between the bigger water bodies (so no, it's not actually a river). The East River passes the "mainland" (The Bronx) and numerous islands are touched by its saltwater flows (like Manhattan, and Long Island (Queens and Brooklyn are part of this island)). Other smaller islands, like South and North Brother Islands, which are not currently inhabited by people, and Randall's Island, are fully surrounded by straits*.

Randall's Island is really an amalgamation of terra firma. Its current state shows you just how much humans can impact land and water. We united apparently three formerly disconnected islands, including Ward's Island, Randall's Island, and the Sunken Meadow island. Looking at the Historical NYC Maps & Atlases, you can see three distinct islands up until 1922 (maps from at least 1839-1922 show 3 islands). While we had many impacts including deforestation by using the land itself , in the last hundred years, we also altered this area by joining the islands.

By zooming in on the map created by the Wildlife Conservation Society Welikia Project (formerly Mannahatta Project), you can see that marsh fringed all of the three islands that are currently connected. You can click on the sections and it reveals that while the higher areas of the islands were covered in forest, the lower areas contained high salt marsh, low salt marsh, marine eelgrass meadow, marine intertidal mudflats, salt shrub, among other ecological community types. According to Ted Steinberg's Gotham Unbound, nearby salt marshes in Queens and Manhattan were filled in with construction debris, refuse, soil, and other materials; presumably the islands were joined in the same way, eliminating at least the interstitial habitat. By looking at a Google Map or walking around the island, you can see that most of the edge of the current island is not currently fringed by marsh or any of these other coastal ecological communities either.

Spartina alterniflora (Saltmarsh cordgrass) on the edge of current Randall's

But another way that humans can impact land is by restoring habitats that we formerly displaced. One of the reasons is that birds that used to use these areas still need the feeding and breeding spots that habitats like low salt marsh provide. Randall's Island Park Alliance has restored several areas of watery habitat on the island, including high marsh, low marsh, and freshwater marsh. My understanding is that the freshwater marsh (although not necessarily historically present) is used to act as a buffer for some of the runoff from athletic facilities and parking lots on the island.

Protective fencing for the north shore habitats (look closely)

These restored habitats are still under tremendous pressure from humans, including being degraded by pollutants we release, being taken over by invasive species that can change the area into a monoculture, and having sensitive plants trampled and animals disturbed by people who don't yet know or care about the habitats. I am fortunate to work for an organization that had been able to help these areas, and I even got to make a video about it. One of the things that I tried to get into the video, but had trouble explaining in short soundbites, was that removing the phragmites fit the long-term restoration plan for the areas. It will take years to mitigate some of these issues, and we will probably always have to actively manage them to keep the habitat restorations healthy.

More than 150 species of birds have been spotted on Randall's Island. I heard a Yellow Warbler in the freshwater marsh today and spotted a Yellow-crowned Night Heron on a post in the water by habitat on the north shore we were fencing (picture to come shortly- I got it on someone else's camera!). Ebird contains some user-submitted data and this NYS ebird Hotspots website can help you break it down; one observation I have is that there are not a lot of checklists yet compared to nearby spots, so there is plenty of opportunity for contributing meaningful data. You might even spot something rare like 2014 Barnacle Goose (pictured below), or spot some of the 16 sparrow species that have been recorded there in fall, winter, and spring.

*At least one of the maps, including 1781, show that Manhattan and the Bronx used to be connected in a very small area what is just northeast of today's Inwood and south of Spuyten Duyvil and Marble Hill. I have been told by a friend familiar with the natural history of the area that historically they were connected by salt marsh, so that at low tide it was possible to cross (perhaps getting wet, but still able to walk across). Historically, and more so now (with no salt marsh in the way), the Hudson River is connected to the East River by the Harlem River, yet another strait. Little Hell Gate, the waterway between current Randall's Island and the Bronx, is really part of this complex of water connections, and may be much transformed from its state two hundred years ago.

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