Since the time of Malthus, humanity has worried whether there would be enough food to feed the growing population. Such fears were always overcome and doomsayers all proven wrong: there was always more land to grow our crops when existing croplands failed to deliver, and new ways to get more yield from old crops.

Today our planet appears very finite, and the only places to expand agriculture are in our remnant natural grasslands and tropical forests. And the demand for more agricultural crops is relentless, due to not only our rising population, but more importantly, our rising prosperity. The expected 4 billion new members of the middle class who will join the rest of us by 2050 will likely demand more dairy and meat. These require an enormous amount of grains to produce.

Add to these the demands biofuel places on agriculture, and we need to boost global agricultural production by 60% to 110% by 2050. To put this challenge in a time perspective, that kind of increase took our ancestors 10,000 years to achieve.

So how are we doing? My research team recently published an analysis in PLOS ONE of the local to global scale performance of maize, rice, wheat and soybeans. These are the top four global crops, collectively responsible for nearly two-thirds of all agricultural calorie production. We found that current rates of productivity improvements are nowhere near the rates of productivity gains (2.4% per year) required for growing demand. Instead of the required doubling of crop production by 2050, at this rate the yield increase will be only 38% to 67%, with the problem more acute for rice and wheat.

Australia, is the ninth largest global producer of wheat and a major exporter. Its wheat yields have declined at 0.7% per year. In fact, we observed negative yield trends in around 80% of Australia’s wheat cropland areas.

Productivity was rising in only a few of the important wheat cropland areas: the South Eastern statistical division in New South Wales; Darling Downs in Queensland; Goulburn, Western district and Central Highlands in Victoria; south eastern region in Western Australia; and outer Adelaide, Murray Lands, and Eyre in South Australia. Even in these regions the rates of wheat productivity improvements were below the 2.4% rate required to double wheat production, except for south eastern region of New South Wales, where we estimated the rate to be 3.4% per year.

Does this mean Australians won’t be able to feed themselves, much less feed others, with wheat? It seems very unlikely at only 0.7% per yearly declines. This decline however may worsen as Australian agriculture matures. Australian wheat yields are limited by lack of nutrients and of water, with the latter being a bigger factor as we reported in a paper published in Nature last year. In some areas of Australia wheat productivity was already at the maximum possible value.

Looking beyond Australia, we found many countries where the gains in crop productivity are less than those required to keep pace with their population growth. In several countries – such as Guatemala and Kenya – productivity of maize, a significant source of daily dietary energy, is declining and population is growing.

In Indonesia – the third largest rice-producing nation on Earth where rice provides about 49% of daily dietary energy – productivity gain is too low to keep pace with population growth. In India, China, Philippines and Nepal, productivity improvement rates in rice are just about enough to maintain per capita production at current levels.

Although supply will not meet demand by 2050, all is not lost. We can close the demand–supply gap in one of many ways. We can invest more to boost crop productivity in the faltering regions that we identified. We can bring more of our remaining natural lands under production (but wheat alone would require 95 million additional hectares, more than the total area of New South Wales). We can reduce food waste, which already accounts for nearly half of global crop production (unfortunately, waste sometimes is difficult and expensive to reduce, as in developing nations where it occurs between farm and table due to lack of storage and transportation).

Perhaps most controversially, we can change to more plant-based diets. Nobody really knows what members of the new middle class will choose to eat. History shows time and again that as people join the middle class, they look for more dairy and meat. But if they go against previous trends and decide to keep consumption of animal products low – if those of us already in the middle class reduce our meat consumption – we may all have enough to eat after all.

Research support was provided by a grant from the Gordon and Betty Moore Foundation, and by the Institute on the Environment, along with previous funding from National Aeronautics and Space Administration's – NASA’s – Interdisciplinary Earth Science program. This work also benefitted from contributions by General Mills, Mosaic, Cargill, Google, PepsiCo, and Kellogg to support stakeholder outreach and public engagement. These organisations had no say on the published report or this article.

This article was originally published at The Conversation. Read the original article.