Abstract
The population of the world has increased drastically, and the increase will continue for some time to come. Various aspects of the impact and interaction between population and food supply are discussed.

This material took the form of a teleconference question and answer session between David Noel of the Tree Crops Center, who asks the questions, and Professor Alex McCalla of the University of California, Davis, who gives the answers.

Q. Alex, in your previous position as Director of Rural Development for the World Bank, you had to look at the big picture. One aspect of this is how the world's population will be fed in the future. Can I ask you if the population level will definitely increase, and if so, how much? And will the increase ever fall off in the foreseeable future?

A. The reality is that once you start a demographic process, it is going to take several generations for significant changes now to influence long-term population outcomes. While the evidence is that the rate of population growth is slowing, it is still fairly clear, I think, based on UN projections, that the world's population will be between seven and a half to eight billion people by about 2030. Depending on how optimistic you are at that point, about whether or not death rates continue to stabilise and birth rates continue to come down in the high birth-rate areas such as Africa, as they have come down in Asia, substantially in India, for example, there is some notion that global population might stabilise in the nine to ten billion number somewhere in the period 2050 to 2100. But I think it is inescapable than in the next 25 to 30 years there is most likely going to be about 2 billion more people to feed than there are now. Population reached 6 billion in 1999 and is now working on the seventh billion. It will be a real challenge to feed that population; I think that is the major issue.

Q. So it isn't just a matter of falling birthrates, falling percentages of fertility, but also a matter of people living longer, so even if the rate of increase gets down to zero, the population will still continue to increase for many more years?

A. Right. The long-term debate is on how long will population growth rates go. What has happened in the post-war period is that death rates dropped much more than birth rates, so that there was a very rapid increase, which is called a demographic transition, which is generally talked about as going from high death rates and high birth rates to low death rates and low birth rates. But in the intermediate stage, there is a stage when death rates drop much more rapidly than birth rates, and there is an explosion of population, 3 to 3.5 % in some parts of Africa, for example.

Now, the reason death rates fall is because we have learned how to control diseases, we are doing a better job with nutrition, etc. Life expectancy has increased substantially, which means people are living longer, and that is good: we shouldn't be unhappy about that. But that is going to take a while to play through the system, so there is no way in the world we are going to avoid having seven and a half to eight billion people by 2030.

The challenge is not just that there will be 2 billion more people, a 25% increase from our current level. That in itself is a big challenge. That is going to require an increase in food production that is comparable to what we took 20 or 30 or 40 years to do the last time we increased 2 billion. But it is more complicated than that for a couple of reasons. Most of that increase, 95% of that increase in population will be in developing countries. Population growth rate in developed countries, the rich countries, is not very much above replacement level, in some cases, below replacement level. There are negative population growth rates in some of the countries in eastern Europe, for example.

So, most of the increase is going to be in developing countries. Those are going to be developing countries which are between the tropics, the Tropic of Cancer and the Tropic of Capricorn. Probably 95% of the 2 billion will be in that area, both tropics and subtropics, both arid and humid. So, if we look at what has happened over the last 40 years, namely, what happened from 1960 to 2000, as we more than doubled world population, we doubled food production in that period. We doubled grain production, for example. But the share of that grain production that was traded remained basically the same share, about 10 to 12%. To state it another way, that means that 90% of that food production was consumed in the country in which it was produced. If we think about it in that way, that says that there has got to be a very large increase in food production capacity, or food production potential, in the tropics. That is a complicating factor because these are farming systems that are complex, populated by and large by small farmers, with multiple crops, multiple animals, perennials, annuals, the whole complicated issue. They are farming systems which generally are heavily stressed, both biotically, with pests and diseases, and abiotically, with either drought, heat or too much rain. To complicate it even further, they are populated by crops about which we know relatively less than we know about temperate zone crops. We know a lot less about cassava, yams or sweet potatoes or some of the exotic pulses, than we do about wheat, rice, maize. So if you think about all that, it is a much more complicated farming system, it is a farming system about which we know less, yet it is going to bear, if this past trend continues--if trade is not going to solve the problem--then those farming systems have got to substantially increase their productivity. That, it seems to me, is a biological and physical science challenge, plus a social science challenge, of unprecedented magnitude, in terms of global history.

Two other things about those farming systems. One is that all indications are that they are the farming systems most likely to be negatively impacted by global warming. They are closer to the equator, the more likely they are to have less rain, more heat, so they are more likely to be impacted more than some temperate areas which will get a positive kick out of global warming, some parts of North America, perhaps Australia. So that is an additional dimension to it.

The last additional dimension is that these are areas in which there is incredible pressure on the natural resource base, in terms of deforestation, in terms of being on the desert margin, desertification, and so forth. And yet, it seems unlikely to me that we are going to meet the additional food supply by bringing more land into production or bringing more land under irrigation. I think we have about reached the limits of arable land and water for irrigation. It is a huge challenge.

The second part of it is that the urban populations in the cities of developing countries is going to increase by two to four billion people in the same period. So in general terms there will be a lot more people living in cities than now, in the developing world. That has implications for the food marketing system. People who live in rural areas on subsistence agriculture generally depend on what they produce or acquire locally for 60 to 80% of their food supply. People who live in cities depend on markets for most of their food supply. Every time you have a translocation of someone from rural to urban, it means that the marketed surplus must double. If we need a 25% increase in food production, we need a 50% increase in marketed food in the cities of the developing world. I think that is an enormous challenge in terms of infrastructure, in terms of food safety, in terms of nutrition. I don't want to sound like a Malthusian, because I'm not. I don't want to sound like I'm crying wolf and saying we are going to run out of food, because we are not. Clearly, we are capable of producing it. The question is, can we produce it in the right place and can we move it from where we produce it to where the people are.

There are two other challenges that I will quickly mention. One is that most of the poor people in the world are farmers in the developing countries. If we want to improve their access to food, because poverty is the major cause of under-nutrition, not lack of food supply, improving the income of small farmers in developing countries would be a tremendous impact. It would be a tremendous impact to help them generate income and it would also help keep food prices low. Low food prices are very important to poor people in the cities, as well as poor rural people who buy food. Agricultural development in the tropics and subtropics would contribute to the food supply and also can contribute to income generation. Last, but not least, if it is done right, it can contribute to the preservation of natural resources.

I see the challenge facing agriculture in the future as being very, very large and substantial.

Q. Do you think migration, moving people from one area to another to get them into areas where food is more readily available is beneficial, or is the reality too large-scale for this to have any influence?

A. If you look at the overall implications of migration for population, country by country, there are probably areas where you have adjacent countries with relatively small populations where a significant share could move across the border. But if you look at global population projections of the sort I was talking about earlier, migration is infinitesimal, it is really very, very small. If you think about the number of people--if you are going to add eighty million people a year and you ask, how many people would we have to move in a day to have any significant impact, and it's a lot. I think the reality is that while migration in some areas and some places may have significant impact in relative population, but in terms of the aggregate, you are not going to move enough people out of the tropics into the temperate zone to let them be fed by temperate zone farmers.

Q. In a way, you are saying that in order to meet the problem, we have to be able to move the technology, the expertise, rather than the people in order to improve their efficiency and their level of food production?

A. Just to put it in a slightly different way: we are going to have to help the people in the tropics to develop the technology that allows them to increase productivity in agriculture, both to make incomes higher and to contribute to food supplies. Yes, the technology has got to develop there. International science can help. I think the possibilities of modern molecular biology are tremendous, if we can get over the problem of Luddites not allowing it to move. It seems to me that the technology must be developed indigenous to the area in which the people are going to grow the food. We can help, but we can't just transfer things.

Q. One of our local speakers at this conference is a strong advocate of what he calls the 'door' approach to research. His aim is to develop the mindset that people will do research on what they are currently active on, rather than expect the government to do it for them, or to bring it in, overseas aid, to put the experts 'on tap.'

A. Yes, we are rapidly passing the day in which there is the notion of 'scientific imperialism.' That scientists sitting in their research stations, through their extension agents, know better than the farmers what to do and what the problems are. I think there is a tremendous amount to be learned from farmers in place in farming systems, in some places called 'indigenous research.' We certainly need to be interacting with them more effectively in terms of scientific priority-setting, and having them identify what their problems are and how they would like to solve them, and then seeing if we have anything to contribute to that, which is a vastly different approach than we have taken historically. I think it is not to be done in the context in which we expect the research to pay off. It is not going to be something you can import from Perth or from Davis and plug into equatorial Africa.

Q. Our conference is about tree crops, which we take to be all perennial plants which produce useful products, especially food. We see tree-based food production systems as being more productive, more stable, much kinder on the environment than field crops. People have suggested that no nation with a strong tree crop system of producing its food has ever been subject to famine, which seems a reasonable assertion. Of course, we understand that these tree-based systems may take longer to set up and produce, but it seems to be a good way to go. Tree crops seem to be, ultimately, more productive and more stable. Do you have any comments on that?

A. If you go back and remember that I said there were three challenges facing global agriculture. One was simply producing the necessary food. Trees are a much more significant part in complex farming systems between the tropics than they are now in terms of temperate zone monoculture agriculture, and always have been, for that matter. I think that there are many, many tree species that are under-utilised, that are very productive. I think that what we are looking at is mixed farming systems in which we have all three: perennials, annuals, and livestock. We cannot ignore the fact that as people become better-off, they consume more livestock products. Clearly the role of trees in this process has to be large. One, in simply producing foodstuffs. Two, thinking in terms of rural development: what we are facing in many countries is substantial under-employment in rural sectors, and substantial under-income. Tree crops tend to be higher income-earning than field crops, and secondly, they tend to employ more labour, so you get a kind of double benefit out of it. If you think about producing tree crops, or vegetables, annual or otherwise, you have a much more intense use of labour than producing corn or wheat or rice. You get employment out of it and you get income.

The third point is that I think the evidence is pretty good that when you go to monoculture, particularly monoculture of annual crops, in tropical areas that are hilly and undulating and have wide variation in moisture, the role tree and perennial crops can play in environmental stewardship and the management of natural resources is substantial. It still shocks me to go to countries in the tropics and see 45 degree hillsides denuded and farmers ploughing up and down to plant sweet potatoes or maize. We know that half of that hillside is going to be in the creek in the bottom of the gully before the next rainstorm is over. There is a strong ecological role for trees to play.

Q. Here in Australia we see ourselves as part of two worlds, being, as far as I can see, the only fully developed country with extensive tropical areas. Do you think this gives us special opportunities, or special responsibilities, perhaps, in trying to achieve the changes you have touched on?

A. I think Australia has already made substantial contributions. My days in the World Bank gave me a clear indication of that. Here you have a country with significant scientific capacity, with the latest training and putting significant resources into it, which is addressing the issues of tropical agriculture. No other country in the developed world does that. There is a little of this in Hawaii and maybe some in Florida, but basically Australia is the only country that does both. In that sense, I think there is an unusual opportunity and an unusual challenge, and I suspect I would also look on this as an obligation. It is something--not to say that I think that what Australia does best in Cairns in sugar production, etc., but rather that we have scientists and experts who understand the biotic and abiotic stresses of tropical environments, of heat and humidity and disease, that people who come from temperate environments don't know and have to learn. That doesn't mean they can't learn it, but Australians sort of have it built in.

Q. I guess you in California have one of the most important tree crop industries in the world. I guess both of us would like to see continuing cooperation between these two sides to work along the different directions and face the various problems that are coming up.

A. My sense is that the California tree fruit industry is being buffeted not only by the traditional issues of disease--we currently have a serious problem with Pierce's disease in grapes, for example. We always have had a Phylloxera problem. We have the traditional problems of root stocks and viruses, etc. I think that California more than Australia is now an agricultural environment in an increasingly tight, urban coat, all the way around. I think what is happening is that the rate of loss of agricultural land in California is in the range off 30 to 50 thousand acres a year, and that is from a fairly small base of irrigated agriculture. So that there is not only the issues of air pollution as impact on productivity, but a whole set of issues about the interface between an agriculture that uses chemicals and fertilisers and an urban environment that is constantly encroaching on it. This raises a very interesting and different set of questions for Californian agriculture that perhaps no other agriculture in the world faces right now. We still will learn from you folks because you are going to have the same problems, perhaps of a lesser magnitude, as time progresses.

Q. I take it you are losing land for agriculture to urbanisation, buildings. Is that the main source of the loss of your land?

A. Yes. I am teaching a class this term. I found a map that showed the urban land in northern California in 1940 versus 2000. It is incredible that there are a few red blotches in 1940 and there are big red swatches in 2000. The population of the central valley in California doubled in the last ten years. It is going to double again in the next ten to fifteen years. That is entirely because the San Francisco Bay area is basically full of houses. The Santa Clara Valley is already gone to Silicon Valley. So you have housing moving, steadily and inexorably into the central valley. Where I live in a town next to Davis the population 15 years ago was 2500. Now there are 18,000 people and growing very rapidly, mostly by urban dwellers who work in the Bay area. That is happening up the corridor to Sacramento, the corridor to Stockton. Enormous numbers of houses, paving over really very good farmland.

Q. Do you think you will ever get to the stage where you will have to import food into California?

A. California agriculture would probably be surprised to find out there is already a significant portion of our fresh fruit and vegetables that are imported at certain times of the year. If I go to the store right now, I am going to find Chilean grapes and Mexican avocados and Honduran raspberries and cut flowers from Colombia, so I think it is already happening, in the sense that you have a year-round market filled with produce from wherever it happens to come from. I don't see anything to change that in the near future.