Just how many people can world agriculture sustain?That was among the questions considered by leading ecological and environmental scientists at a workshop at Lincoln University's Bio-Protection Research Centre last month.
Known as the Geographically Appropriate Integrated Agriculture Workshop (Gaia), its objective was to develop and evaluate a range of scenarios for agricultural land use and management from the perspective of ecosystems and the fundamental services they provide.
The 23 participants in the workshop - from countries such as Denmark, the United Kingdom, the United States, the Netherlands, Kenya and Australia - built on developments in agro-ecology to estimate how many people the world could sustain without the current dependence on, and over-use of, water resources and fossil fuel-based chemicals such as fertilisers and pesticides.
Such questions were highly relevant next to the intensive use of the planet's resources, which has been estimated to be at a rate about 50% higher than the planet can maintain. Under the workshop's proposed scenario, it was estimated the Earth was suited to a population of about 4.2 billion - three billion fewer than its current population.
Agriculture operates on about 40% of the Earth's surface, making it the planet's most significant terrestrial ecosystem, but also one that has developed through the deliberate designs of humankind. While the contribution agriculture has made to the life-supporting development of our species is immense, it has also impacted negatively on ecosystems and biodiversity - the fundamental systems that keep people alive, the workshop suggested.
''It is widely acknowledged that agricultural lands show a steady decline in ecological asset quality,'' Lincoln University ecologist Prof Steve Wratten, one of the principal organisers of the workshop, said.
''This jeopardises the production of other important ecosystem services that are critical to sustainable, healthy living.
''Much research and investment in agro-ecological practices, however, has shown that it is possible to substantially reduce dependency on non-renewable resources.''
One key output from the workshop will be a series of papers for a special issue of academic journal Ecosystem Services, as well as a paper intended for a high-profile journal such as Nature.
The week also included presentations by three of the workshop delegates at a special forum held at Environment Canterbury (ECan). There was a high level of interest in the forum, which was aimed at stimulating discussion around the consideration of ecosystem services in future policy.
Prof Robert Costanza, a leading ecological economist and author of many books on public policy, environmental management and sustainability, spoke on the importance of resource economics, which values the natural capital that delivers ecosystem services, and stresses the need to include ecological considerations in the commercial realm.
He also advocated for the advantages of utilising the Genuine Progress Indicator (GPI) as a more credible and ''full cost accounting'' measure of wellbeing and equality than GDP.
The ECan forum also saw Prof Wratten speak on how crop monocultures can be diversified to improve functional biodiversity, reduce costly inputs and, crucially, increase farm profits. He noted the giant grass miscanthus could deliver about 14 beneficial ecosystem services on dairy farms alone and, when planted around paddocks, could contribute to a farm's overall financial and environmental stability.
Sasha Courville, a senior manager with the National Australia Bank who specialises in commercial strategies around sustainable investment with consideration for true natural value, also spoke.
She is developing a link between improvements in environmental management and farming financial packages.
In recent decades, there has been a greatly improved understanding of ecosystems and, more specifically, the vitally important goods and services they provide: goods and services, that is, that have often been taken for granted or overlooked in commercial and social decision-making.
Improved research in recent times has led to more sophisticated skills in modelling and simulating the dynamic complexity of ecosystems, leading to a better understanding of where market and institutional failures may be causing the unintentional depletion of natural and ecological assets.