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The University of Southampton
Biological Sciences

Research project: Enhancing ecosystem functioning to improve resilience of subsistence farming in Papua New Guinea

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Papua New Guinea (PNG) has the world’s richest island flora and 85% of the population depends entirely on small-scale agriculture. The overall aim of this PhD project is to offer practical solutions to farmers (e.g., soil management, selecting nutritious crops, increasing on-farm biodiversity) to increase their food security using a socio-ecological approach.

Increasing agricultural production in high biodiversity tropical areas, alongside a growing population, and climate change, is an increasing challenge in many countries with tropical climates. Such pressures are particularly relevant to Papua New Guinea (PNG), which has the third largest area of tropical forest worldwide, and where 85% percent of the population depends almost entirely on small-scale agriculture. Crop yields are well below regional averages and PNG has the fourth most under 5-year-old stunted children in the world. 

Most farmers practice swidden agriculture in PNG that involves clearing and burning a forest patch, growing crops in small fields (gardens), then leaving the fields to fallow so the soil can regenerate. Then the fields are burnt and cultivated again. Due to population growth, farmers need to cultivate gardens longer and re-use fallowed land before the soil can regenerate fully. Between 2001-2019, PNG has lost 1.49 million hectares of tree cover which is equivalent to 789Mt of CO2 emissions.

The overall aim of my PhD is to increase food security of small-scale farmers using a socio-ecological approach and investigate agriculture-driven deforestation in PNG.

Objective 1: Characterise forest gains and losses due to swidden agriculture in PNG and investigate the expansion of small-scale forest clearings into primary forest areas.

Methodology: Ensemble species distribution models (SDMs) will be constructed from over half a million observations from online databases. SDMs will be stacked to estimate biodiversity hotspots. Using high resolution satellite imagery by Planet, I will develop a remote sensing tracking system of garden cultivation, estimate swidden agriculture expansion into primary forests and cross-validate the apparent land-use changes with field observations in Madang province. 

Objective 2: Identify crop diseases along the Mt Wilhelm altitudinal gradient (250-3,400 m), estimate pdisease load based on disease symptoms, investigate the role of on-farm crop diversity and explore farmers’ attitudes towards crop disease and pest management.

Methodology: I will collect diseased crops for microscopic identification and survey farmers’ existing crop management practices using semi-structured interviews. Community pathogen load will be estimated based on symptoms categories, diseased leaf/stem area, and crop diversity along the altitudinal gradient, where previous surveys found that 92 crop species are grown by farmers for consumption. The effect of elevation, garden age, and crop diversity on pathogen load will be tested.

Objective 3: Determine the effect of soil management practices on sweet potato yields within the swidden agricultural system and investigate the underlying mechanisms (soil nutrient availability, microbial gene abundances) behind the different cultivation methods with metagenomics. 

Methodology: Working with farmers, we will apply four treatments (topsoil transplantation, bokashi fertiliser addition, NPK fertiliser, and control) at highland (1,500 m) and lowland (200 m) locations in freshly cleared and few-years-old experimental gardens. Using high throughput soil metagenomics, I will investigate the abundances of genes involved in P- and N-cycling and how the gene abundances are impacted by different soil treatments.

Landscape of Papua New Guinea
Landscape of Papua New Guinea

Objective 4: Investigate the diversity, potential yield and nutritional value of sweet potato varieties from the national germplasm collection and survey households’ nutritional intake.

Methodology: There are over 1,008 accessions of sweet potatoes catalogued and about 5,000 landraces of sweet potatoes are estimated to be grown by farmers in PNG. Despite their incredible diversity, not much is known of their potential yields and nutritional values. I will use molecular markers that are associated with dry matter, starch, β-carotene, flesh colour and total root yields to investigate the diversity of sweet potato varieties and investigate the driving forces behind cultivar selection by farmers.

With our collaborators at the New Binatang Research Centre, we will work closely together with local communities and hope to offer practical solutions (e.g., crop management, growing nutritious cultivars, increasing on-farm diversity) to farmers to increase their food security whilst investigating underlying ecological processes (soil functioning, changing landscapes).

Research student: Juniper Kiss


Becky Morris
Jake Snaddon

Funding provider: UKRI NERC INSPIRE DTP
Funding dates: 10/2020 – 03/2024

Related research groups

Ecology and Evolution
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