Plastics dumped into the world's oceans may outweigh fish by the year 2050, United Nations Secretary-General Antonio Guterres said Monday during the opening remarks of the first-ever , citing .

In his speech, Guterres issued dire warnings on the state of the world's oceans, saying they are "under threat as never before."

"Pollution, overfishing and the effects of climate change are severely damaging the health of our oceans," he said. "According to one recent study, plastic could outweigh fish — if nothing happens — in our seas by 2050."

Representatives of nearly 200 countries convened at the U.N. Headquarters in New York City for the five-day conference that also marked World Environment Day on Monday.

According to a press release, Guterres told attendees that oceans, whichare "the lifeblood of our planet," and notedthe aim of the conference is "to turn the tide" and solve the problems that "we created."

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Coming less than a week after U.S. President Donald Trump announced the , Guterres stressed"the problems of the ocean — all created by human activity, can all be reversed and prevented with decisive, coordinated action," adding thatcompeting interests over territory and natural resources have no place in the fight to save the health of the world's oceans.

"Oceans are a testing ground for the principle of multilateralism," he said. "The health of our oceans and seas requires us to put aside short-term national gainto avoid long-term global catastrophe."

"Conserving our oceans and using them sustainably is preserving life itself," he added.

Said General Assembly President Peter Thomson of Fiji: "The time has come for us to correct our wrongful ways."

"We have unleashed a plague of plastic upon the ocean that is defiling nature in so many tragic ways," he said. "It is inexcusable that humanity tips the equivalent of a large garbage truck of plastic into the ocean every minute of every day."

Thomson notedillegal and destructive fishing practices and harmful subsidies for fisheries "are driving our fish stocks to tipping points of collapse" and reiterated scientific evidence that human-produced carbon emissionsare not only driving climate changebut also causing rising sea levels, which in turn, makes them more acidic with less oxygen, harming marine wildlife.

He said the conference may become the best opportunityever "to reverse the cycle of decline that human activity has brought upon the ocean."

Micronesian President Peter Christian, in an apparent dig at Trump's decision to pull out of the Paris Accord, emphasized the importance of the landmark agreement, according to the Associated Press.

“While some may continue to deny man’s culpability for the damaging effects of climate change on islands and islanders ... no man, no island, no village and no nation can deny that trash in our oceans is of man’s own doing [and] man must clean up his mess,” he said.

Bolivia's Evo Morales took accusations a step further bytelling the conference attendees that the government of the United States, one of the world's "main polluters," decided to leave the Paris agreement, "denying science, turning your backs on multilateralism and attempting to deny a future to upcoming generations."

This "has made (the U.S.) the main threat to Mother Earth and life itself," Morales said, as reported by the AP.

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On Friday, the nearly 200 countries will issue a Call for Action to address marine issues, which urges nations to implement voluntary long-term measures to reduce the use of plastics and counteract sea-level rise that threatens the economies of many island nations, rising ocean temperatures and increasing ocean acidity under U.N..

“The Ocean Conference is where we truly begin the process of reversing the cycle of decline into which our accumulated activities have placed the Ocean,” Thomson said. “By adding to the conference’s register of voluntary commitments; of producing practical solutions to Ocean’s problems at the Partnership Dialogues; and through the affirmation of the conference’s Call for Action, we have begun that process of reversing the wrongs.”

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Hong Kong

Doug Woodring, an entrepreneur and conservationist who lives in Hong Kong, displays rubbish on May 07, 2009 on a beach on the south side of Hong Kong which has been left uncleaned. (MIKE CLARKE/AFP/Getty Images)