Native mammals and other fauna are crashing in some places. We investigated the potential for disease to be a factor in these declines, and have published our findings.
TitleA guide for ecologists: Detecting the role of disease in faunal declines and managing population recovery.
Preece, N.D., Abell, S.E., Grogan, L., Wayne, A., Skerratt, L.F., van Oosterzee, P., Shima, A.L., Daszak, P., Field, H., Reiss, A., Berger, L., Rymer, T.L., Fisher, D.O., Lawes, M.J., Laurance, S.G., McCallum, H., Esson, C., Epstein, J.H., 2017.
Biological Conservation 214, 136-146. (You can download the article from here until mid-October 2017).AbstractBiodiversity is declining at an alarming rate, especially among vertebrates. Disease is commonly ignored or dismissed in investigations of wildlife declines, partly because there is often little or no obvious clinical evidence of illness. We argue that disease has the potential to cause many species declines and extinctions and that there is mounting evidence that this is a more important cause of declines than has been appreciated. We summarise case studies of diseases that have affected wildlife to the point of extinction and bring together the experiences of wildlife managers, veterinarians, epidemiologists, infectious disease specialists, zoologists and ecologists to provide an investigation framework to help ecologists and wildlife managers address disease as a factor in wildlife declines. Catastrophic declines of wildlife may be the result of single or multiple synergistic causes, and disease should always be one factor under consideration, unless proven otherwise. In a rapidly changing world where emerging infectious diseases have become increasingly common, the need to consider diseases has never been more important.
Cape York Peninsula
is an extraordinary and beautiful place and is home to the richest fauna and flora of any region in Australia. It is also the home to lots of people, both Indigenous and non-Indigenous, many living off the land. So how do people make money without destroying the land they (and we) depend on? We looked closely at the benefits derived from good land management and published our findings.
TitlePreece, L.D., van Oosterzee, P., Dungey, K., Standley, P.-M., Preece, N.D., 2016. Ecosystem service valuation reinforces world class value of Cape York Peninsula's ecosystems but environment and indigenous people lose out.
Ecosystem Services 18, 154-164.AbstractCape York Peninsula's iconic status relies on its world-class landscapes and continuity of Indigenous occupation. Contests between economic, environmental, cultural and social interests have not considered valuations of ecosystem services. This first valuation of Cape York's ecosystem services asks the question: who is winning and where? The total ecosystem services value of Cape York is estimated conservatively to be AUD $130 billion per year. The value for each biome ranges from $0 ha−1 y−1 in ‘non-remnant’ areas, to $602,000 ha−1 y−1 for coral reefs. Ecosystem services value is comparable to the region's largest industry, bauxite mining. Mining has produced great benefits to the economy, but local communities remain disadvantaged, receiving a fraction of the ecosystem services value, estimated to be worth $120 M. The productivity of grazing lands is $18 ha−1 y−1, compared to the ecosystem services value of at least $3,300 ha−1 y−1. We argue that the high ecosystem services value of Cape York is because of Indigenous land management over millennia. Since the disenfranchisement of Indigenous people, ecosystems of northern Australia have suffered significant land degradation. A policy framework is required that acknowledges the value of ecosystem services and also incentivizes the cultural ecosystem services of Cape York.
Ferals and weedsNoel has worked for decades on feral animals and weeds, and was recently interviewed on ABC radio about the history, impacts and future of feral animals (and plants) across Australia. The interview is available as a podcast. Here’s the podcast:
http://www.abc.net.au/radio/programs/overnights/feral-animals/7916106Weeds also feature in an article published with colleagues - Strawberry Guava - lovely fruit - has become a serious problem in the wet tropics. We published an article about the impacts.
Tng, D.Y.P., Goosem, M.W., Paz, C.P., Preece, N.D., Goosem, S., Fensham, R.J., Laurance, S.G.W., 2016. Characteristics of the
Psidium
cattleianum
invasion of secondary rainforests.
Austral Ecology 41, 350-360.AbstractStrawberry guava (
Psidium cattleianum) is a shade-tolerant shrub or small tree invader in tropical and subtropical regions and is considered among the world's top 100 worst invasive species. Studies from affected regions report deleterious effects of strawberry guava invasion on native vegetation. Here we examine the life history demographics and environmental determinants of strawberry guava invasions to inform effective weed management in affected rainforest regions. We surveyed the vegetation of 8 mature rainforest and 33 successional sites at various stages of regeneration in the Australian Wet Tropics and found that strawberry guava invasion was largely restricted to successional forests. Strawberry guava exhibited high stem and seedling densities, represented approximately 8% of all individual stems recorded and 20% of all seedlings recorded. The species also had the highest basal area among all the non-native woody species measured. We compared environmental and community level effects between strawberry guava-invaded and non-invaded sites, and modelled how the species basal area and recruitment patterns respond to these effects. Invaded sites differed from non-invaded sites in several environmental features such as aspect, distance from intact forest blocks, as well as supported higher grass and herb stem densities. Our analysis showed that invasion is currently ongoing in secondary forests, and also that strawberry guava is able to establish and persist under closed canopies. If left unchecked, strawberry guava invasion will have deleterious consequences for native regenerating forest in the Australian Wet Tropics.
Carbon sequestration
has become an alternative farm income for some. But how do farmers optimize their carbon plantings with their other farm income? We investigated.
Paul, K.I., Cunningham, S.C., England, J.R., Roxburgh, S.H., Preece, N.D., Lewis, T., Brooksbank, K., Crawford, D.F., Polglase, P.J., 2016. Managing reforestation to sequester carbon, increase biodiversity potential and minimize loss of agricultural land.
Land Use Policy 51, 135-149.
AbstractReforestation will have important consequences for the global challenges of mitigating climate change, arresting habitat decline and ensuring food security. We examined field-scale trade-offs between carbon sequestration of tree plantings and biodiversity potential and loss of agricultural land. Extensive surveys of reforestation across temperate and tropical Australia (N = 1491 plantings) were used to determine how planting width and species mix affect carbon sequestration during early development (<15 years). Carbon accumulation per area increased significantly with decreasing planting width and with increasing proportion of eucalypts (the predominant over-storey genus). Highest biodiversity potential was achieved through block plantings (width ~ 40 m) with about 25% of planted individuals being eucalypts. Carbon and biodiversity goals were balanced in mixed-species plantings by establishing narrow belts (width~ 20 m) with a high proportion (>75%) of eucalypts, and in monocultures of mallee eucalypt plantings by using the widest belts (ca. 6–20 m). Impacts on agriculture were minimized by planting narrow belts (ca. 4 m) of mallee eucalypt monocultures, which had the highest carbon sequestering efficiency. A plausible scenario where only 5% of highly-cleared areas (~30% native vegetation cover remaining) of temperate Australia are reforested showed substantial mitigation potential. Total carbon sequestration after 15 years was up to 25 Mt CO2-e year−1 when carbon and biodiversity goals were balanced and 13 Mt CO2-e year−1 if block plantings of highest biodiversity potential were established. Even when reforestation was restricted to marginal agricultural land ($2000 ha−1 land value, 28% of the land under agriculture in Australia), total mitigation potential after 15 years was 17–26 Mt CO2-e year−1 using narrow belts of mallee plantings. This work provides guidance on land use to governments and planners. We show that the multiple benefits of young tree plantings can be balanced by manipulating planting width and species choice at establishment. In highly-cleared areas, such plantings can sequester substantial biomass carbon while improving biodiversity and causing negligible loss of agricultural land.
- A new allometric model for planted saplings in the wet tropical biome of Australia
- revised biomass expansion factors for young trees
- rare estimates of wood & bark density for young trees in the region
- rare estimates of root:shoot ratios for young trees in the region
- contribution to carbon accounting for wet tropics
Preece, N.D., Lawes, M.J., Rossman, A.K., Curran, T.J., van Oosterzee, P., 2015. Modelling the growth of young rainforest trees for biomass estimates and carbon sequestration accounting. Forest Ecology and Management.
Few measurements for carbon sequestration, ratio of above-ground to below-ground biomass and wood density exist for young trees. Current allometric models are mostly for mature trees, and few consider trees at the sapling stage. Over four years we monitored the growth rates, from seedling to the sapling stage, of 490 trees (five native species) in environmental plantings, in the Wet Tropics of north-eastern Australia.
Our biomass estimates were greater by several orders of magnitude in the first year (6 × 10−3 Mg ha−1 cf. 4 × 10−6 Mg ha−1), and two orders of magnitude less at four years than those derived from the national carbon accounting model (5 × 10−1 Mg ha−1 cf. 13 Mg ha−1). We destructively sampled 37 young trees to accurately estimate the variation in below-ground and above-ground biomass (AGB) with stem size, and to derive a best fit model for predicting sapling biomass: ln AGB = −5.092 + 0.786 ln (Diam.base)2Height.
Biomass expansion factors for young tree species ranged from 1.71 to 2.44, higher than average for tropical forests. Root:shoot ratios are consistent with mean estimates for mature rainforest. Stem wood densities ranged from 0.444 to 0.683 Mg m−3 for the five species measured, which was 6.5% lower than published estimates for three of the species, and 12% and 27% higher for two species. Relative growth rates were faster for species with lower wood density in the first four years, but these species also had the lowest survival over the same period. The findings are significant for a number of reasons.
Ecologically, they indicate that young rainforest trees invest more in leaves and branches than in stem growth. From a survival perspective, in the context of rainforest restoration, it is best to invest in species with higher wood densities.
From a carbon accounting point of view, refinements to the models used for national carbon accounting are required that include the contribution of the sapling stage. Sapling growth rates were significantly different from those assumed in the national model, requiring growth rates to be increased after four years (as opposed to after 2 years in the national model) before reaching an asymptote at some time in the future. This adjustment is essential to enable carbon farmers to judge the time it takes to receive returns from investment. Policies that encourage carbon plantings should take into account that young plantings grow slower than predicted by current national carbon accounting models.