Professor David Field on why the death of the last male northern white rhino must not be allowed to be forgotten.

I met Sudan, the now legendary northern white rhino, who died a week or so ago. He was an amazing animal: big and handsome, but a little stand-offish until, of course, a bucket of food was produced. Sudan was the last male of his sub-species.

It was in 2003 at the Dv?r Králové Zoo in the Czech Republic where he had lived since 1975 in a small breeding herd. Even at that time, the omens for this subspecies of white rhino were not good. Sudan himself had sired three calves and the last calf in the zoo (Sudan's grand-daughter) was born in 2000.

The wild situation was not much better; the only surviving animals were in Garamaba National Park in the Democratic Republic of Congo and, although in 2003 the population reached a high of 32 animals, poaching of the rhinos dramatically reduced the numbers such that five years later it was considered extinct in the wild.

Sudan and his descendants were the only hope – but by then it was probably too late to save this subspecies despite the incredible efforts of conservationists, which included transferring Sudan and three other animals back to Africa in a vain hope that this might encourage natural breeding.

It is somewhat ironic that had Sudan not been taken from Africa to the zoo back in 1975 it is likely that he would have been poached as so many rhinos were killed for their horns. Taking animals from the wild into zoos is not supported now, unless it is part of an international breeding programme authorised by conservation authorities.

Sudan was a subspecies of white rhino. There are still white rhinos in Africa – the southern white rhino. So why should we be concerned?

A subspecies is a defined group of animals within a species which is physically and genetically different from the rest. This has usually arisen because the groups have been isolated from each other. So each subspecies is unique.

Other subspecies of rhinos have gone extinct recently: the western black rhinoceros went extinct in 2011 and even more worrying is that the last Javen rhino in Vietnam was poached in 2011, leaving a population of only about 60 individuals in Ujung Kulon National Park in Java. The countdown is on for the Javen rhino species – the loss of populations or subspecies is a clarion call for ultimate extinction.

Much has been made of the advances in assisted reproductive technologies which may save Sudan's kind. Biobanks of genetic material, in vitro fertilisation techniques and even cloning will eventually be hugely important techniques which will aid conservation and the success of these are increasing.

The development of these techniques will probably be too late for the northern white rhino and in the future will always be only supportive of direct conservation action and habitat protection. After all, we still have to solve the issue of what causes the extinctions in the first place – and for rhinos this is the poaching and killing of rhinos for their horns to supply the illegal wildlife trade. Only once the demand for this horn has been removed will rhinos be safe.

Sudan's demise and the imminent loss of northern white rhinos is hugely symbolic and has rightly caught the attention of the global press. But by next week Brexit or revelations by Stormy Daniels will have replaced Sudan in the headlines.

The extinction pressures on animals, however, be they Javan rhinos, mountain chicken frogs, Bali starlings or water voles (and the list goes on and on) will continue.

There is, though, cause for optimism. The southern white rhino (the 'cousin' of Sudan) was once down to 100 individuals and today, thanks to massive conservation efforts, the numbers are approaching 20,000.

The Zoological Society of East Anglia is working with its partner Save the Rhino to provide funding to support essential aerial surveillance activities to protect and monitor black and white rhinos in the Hluhluwe-iMfolozi Park in South Africa.

Conservation can work! We must hope that the rhino called Sudan does not become a symbol of extinction but a catalyst for renewed support and vigour to defy extinction – a hero for survival!

Prof David Field is chief executive of the Zoological Society of East Anglia, which runs Banham Zoo and Africa Alive! at Kessingland.