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Ma, whose net worth is estimated to be as much as $23.9 billion, reportedly spent $23 million on the property, known as Brandon Park.
Ma's main motivation for the purchase was for conservation reasons, but he reportedly also plans to use it as a vacation home from time to time.
The park comprises more than nine miles of the St. Regis River, several lakes, streams, and a great deal of forestland. It sits in an area of the Adirondacks that is protected by the state of New York; heavy logging and mining work in the late 20th century depleted much of its natural timber and water resources.
Ma has made many donations to conservation efforts in his home country of China, helping to create the Sichuan Nature Conservation Foundation and the Laohegou Nature Reserve in Sichuan.
In 2014, Ma created a charitable trust that now has an endowment of $3 billion.
"Protecting the environment in China will always be Jack's first and foremost priority, and he will continue his strong efforts here," Alibaba spokesman Jim Wilkinson told The Wall Street Journal. "This international land purchase reflects Jack's belief that we all inhabit the same planet and we all breathe the same air, so we are dependent on each other for our collective future."
Brandon Park previously belonged to heiress Wilhelmina du Pont Ross, but it was transferred to a private LLC in 1999. Several homes stand on the property, and there's a barn and several sheds.
Ma became a billionaire after Alibaba's $25-billion IPO in September 2014.
However, he has often spoken about the burden of wealth, saying during a luncheon at the Economics Club of New York: "The money I have today is a responsibility. It's the trust of people on me."