Leonardo DiCaprio calls on UN to combat climate change. IBTimes UK

A new UN report has found the most worrying environmental threats that the world is facing today. It ranges from the increase in disease and epidemics, particularly those transmitted from animals to humans (zoonosis) to the increase in temperatures resulting in accumulation of toxic chemicals in food crops.

The UN Environment Agency's Frontiers report said the 20th century saw a striking drop in the ecosystems and biodiversity. However, it also noted an equally remarkable rise in the human and animal populations in the same period. As a result, this trend has increased the chances for viruses, bacteria and other pathogenic agents to transmit diseases from wild and domestic animals to people through the environment. Zoonotic diseases include Ebola, bird flu, sudden acute respiratory syndrome (Sars) and Zika virus.

Although many zoonotic diseases originate in wildlife, livestock can become a vector for the disease. For example, in the case of bird flu, it first spread among the wild birds, then infected domestic poultry, which passed the virus onto humans.

The UN has estimated that in the last 20 years, emerging diseases have had cost more than $100bn (£68.9bn), and that "if these outbreaks had become human pandemics, the losses would have amounted to several trillion dollars".

"Around 60% of all infectious diseases in humans are zoonotic, as are 75% of all emerging infectious diseases. And on average, one new infectious disease emerges in humans every four months," the report said.

Plastics: Trouble in the food chain

The report also highlighted the risks the increasing amount of plastic waste being dumped into the oceans has on human life. It has cited scientific evidence suggesting that spectrum of climate change causing damages and losses are inevitable, with further adverse consequences for the world's ecosystem, people and economies.

With respected to toxic chemicals in crops, the report states that plants normally convert nitrate – salt that contains nitric acid – into amino acids and protein. But drought slows the conversion, which causes nitrates to accumulate into toxic levels. It said more than 80 common species of crop plants have been known to cause poisoning by nitrate accumulation, with wheat, barley, maize, millet, sorghum and soybeans being the most vulnerable crops.

Poultry Farm
Workers pick up eggs at a poultry farm in Suichuan, Jiangxi Province, China  REUTERS/China Daily

Nitrate poisoning can ruin the livelihoods of small farmers and herders, the report warn that it can also lead to miscarriage, asphyxiation and death in humans.

Other toxins too, such as mycotoxins and aflatoxins, which can cause cancer and stunt foetal growth, are associated with climate change and may increase with temperatures.

Emphasising on how human activities often undermine the "critical relationship between a healthy environment and healthy people", the report has stressed that it is important to enable a global transition towards a low carbon future in order to offset global warming and other environmental issues.