One of Australia’s wealthiest families has committed nearly $5 billion to philanthropy in a share giveaway.

Andrew and Nicola Forrest will donate 220 million shares in their listed mining company Fortescue Metals Group to their philanthropic foundation Minderoo.

The couple established the Minderoo foundation in 2001 and it receives funding through dividends from Fortescue, the company Dr Forrest founded in 2003.

The donated shares, worth about $4.9 billion, make up one fifth of the couple’s shareholding.

“As our world faces enormous challenges, we have elected to continue to use our material wealth to help humanity and the environment meet these existential risks,” Dr Forrest, the Fortescue Metals non-executive chairman, said in a statement.

“Accumulating wealth should only be a small part of a person – their contribution to their family and society is way more important,” he said.

“Other skills such as carpentry, farming, the arts, working in construction, or for government are equally as important.

“If you happen to be good at accumulating wealth, then I believe in using that skill for the greater good,” he added.

Dr Forrest is estimated to be the second richest person in the country, according to two calculations of wealth this year, behind Gina Rinehart.

In May, the Australian Financial Review rich list put Dr Forrest in second place with a personal wealth of $33.29 billion while in March The Australian newspaper’s Australia’s Richest 250 list valued the mining magnate at $35.21 billion, also in second place.

“This donation is a further expression of our unwavering passion to help and in conjunction with our new strategy, will see Minderoo provide more significant support in a focused manner, empower our partners to deliver change and ignite collective and purposeful action including for vulnerable communities, our oceans and gender equality,” Mrs Forrest said.

The Forrests were the first Australians in 2013 to sign the Giving Pledge – a vow also taken by Warren Buffett, Bill Gates and Elon Musk – to give away the vast majority of their wealth during their lifetimes.