It is described as Africa's last eden.
"I'm shocked, I'm completely astounded", he said.
"We started flying the survey on July 10, and we have counted 90 elephant carcasses since the survey commenced", Mike Chase, the charity director, told AFP.
A team of scientists carrying out a survey found that numerous 87 elephants were killed for their horns near the Okavango Delta wildlife sanctuary in Botswana.
An aerial survey was conducted by conservationists Elephants Without Borders over an area near the protected Okavango Delta, and they have since confirmed it is the largest discovery of poaching seen in Africa to date.
A "fresh carcass" is classed as one that has been killed within the last three months but many that are being found have been killed within the last few weeks.
The Botswana Wildlife Aerial Survey 2018 is reportedly only half-way through so, tragically, the number of dead elephants could be even higher.
Poachers had attempted to hide the "mounds of rotting flesh" with drying bushes, the report said.
Botswana has the world's largest elephant population, but poachers have been breaching its border.
"Until now Botswana's elephant herds have largely been left in peace, but clearly Botswana is now in the crosshairs", said Jason Bell, IFAW's vice president for conservation.
Poachers are now going to Botswana, which is home to the world's largest elephant population.
Botswana Tourism Minister Tshekedi Khama confirmed to AFP that dozens of elephants had been poached, but gave no further details.
The government at the time of disarming the anti-poaching unit did not give a reason for the move and has also yet to respond to the latest report.
Tanzania's Selous region, for example, was heavily hit by elephant poachers but recent data indicates that the killing has slowed.
Elephants drink water in the Chobe National Park in Botswana.
He continued: "This requires urgent and immediate action by the Botswana government".
"Our new president must uphold Botswana's legacy and tackle this problem quickly. Tourism is vitally important for our economy, jobs, as well as our worldwide reputation, which is at stake here as being a safe stronghold for elephants." said Mr Chase.
On social media, news of the elephants' untimely deaths was met with fierce outrage.
Its shoot to kill policy was dropped as members of the unit were disarmed. "Save the elephants in Botswana and stop the poaching".