Written by RIEL Adjuncts Dr Don Franklin and Dr Noel Preece
Don Franklin and Noel Preece have just finished a report commissioned by ECNT on the conservation status of Australia's northern eucalypts. The executive summary is set out here, and the full report can be requested from Noel Preece by email at firstname.lastname@example.org
Yellowjacket (also known as Scarlet Gum) (Eucalyptus phoenicea)
We investigated the conservation status of the eucalypt taxa and communities of northern Australia including identification of regions of high species richness and biogeographic note. We did so using records from Australia's Virtual Herbarium (almost 52,000 records) covering the entire range of taxa recorded in our study area, shapefiles of Map Units from The Vegetation of the Australian Tropical Savannas and of the National Vegetation Information System, shapefiles of land clearing and of crown and private conservation reserves, the literature and a miscellany of other sources. We defined northern Australia as the tropical savanna region plus the embedded Wet Tropics and Central Queensland Coast bioregions.
The eucalypt flora of northern Australia comprises 188 species and 38 subspecies (includes one variety) (Chapter 3). All three eucalypt genera are represented, with Eucalyptus being most speciose and Angophora of marginal occurrence in the study area. Eucalyptus is predominant in eastern Queensland and Corymbia in the northern Top End of the Northern Territory. Of these, 105 species and 22 subspecies are strictly endemic to the study area and a further 24 species and 3 subspecies nearly so. Seven species are shared with New Guinea or the Islands of Wallacea to Australia's north. Species richness is greatest in the central and northern Kimberley, the northern Top End and eastern Queensland, with a peak richness of 46 species in the one degree cell covering the Atherton Tableland and adjacent western slopes of north Queensland. Species richness is markedly lower in inland areas but interpretation of the magnitude of this effect is somewhat confounded by reduced collection effort.
Biogeographic analysis showed strong regional patterning with a strong shift in species composition between Queensland east of the Gulf of Carpentaria and areas to the west that is consistent with biogeographic patterns identified among plants and animals in general (Chapter 4). We identified 12 regional groups of taxa with many groups exhibiting high levels of regional endemicity, an analysis that adds substantially to previous biogeographic interpretations of northern Australia.
We developed hierarchically-ranked metrics of restrictedness based on a combination of Extent of Occurrence, the number of degree cells, and the number of records of each taxon, with thresholds derived from IUCN criteria for Extent of Occurrence (Chapter 5). Sixteen species and seven subspecies were rated as extremely restricted (rank 1), while 125 species and 21 subspecies were rated as not at all restricted (rank 5). The greatest concentrations of extremely restricted taxa are in the central and north Kimberley and in the White Mountains area south-west of Charters Towers in Queensland. Restricted taxa (i.e. all except rank 5) are widespread in the central and north Kimberley, the Top End centred on the Arnhem Plateau, and in and around the Einasleigh Uplands of north Queensland.
Applying IUCN criteria, we assessed 19 north Australian eucalypt taxa as Threatened (three as Endangered, 16 as Vulnerable), and an additional nine as Near Threatened and two as Data Deficient (Chapter 5). Seventeen of these assessments were based solely on decline due to clearing (criterion A2b), four were rated on the basis of a combination of rarity and decline due to clearing (criteria B1a,b(ii,v) and B2a,b(ii,v)), and nine taxa were rated on the basis of extreme rarity alone (criteria D1 and/or D2). Taxa we rated as Threatened are strongly concentrated in eastern Queensland. Our ratings differ markedly from official listings of Threatened taxa, with the latter seriously under-representing the level of threat but also rating a number of taxa as Threatened which clearly are not.
Seventy-two of 125 Map Units (communities) in northern Australia are characterised as primarily dominated by eucalypts and a further 12 feature eucalypts as secondary dominants (Chapter 6). Combined, these units cover 69% of the tropical savanna portion of the study area (i.e. Wet Tropics and Central Queensland Coast bioregions excluded).
In the study area, reserves are strongly concentrated in the higher rainfall regions of the north-west and along sections of the Queensland coast especially on Cape York Peninsula and in the Wet Tropics (Chapter 5). There is considerable complementarity between crown and private reserves in their coverage of taxa and communities (Chapters 5 & 6). Eleven species and three subspecies endemic to the study area do not occur in either a crown or private nature reserve, and a further 52 endemic species and ten endemic subspecies have reservation indices of less than 30%. Twelve of 84 eucalypt Map Units are not represented in any crown or private conservation reserve, while a further 40 of these Map Units are poorly represented with less than 10% of their area (and often less than 1%) in conservation reserves.
Land-clearing is strongly concentrated in the south-east of the study area and also along the Queensland coast north to the Wet Tropics (Chapter 5). Targeted assessment of taxa demonstrated indices of clearing of >30% – sufficient to qualify as threatened under IUCN criteria independent of rarity – for eight taxa. A further nine taxa have indices of between 20 and 30%, sufficient to qualify as Near Threatened under IUCN criteria. Five eucalypt Map Units (communities) have been more than 50% cleared and a further three have been 30–50% cleared (Chapter 6). Map Units subjected to extensive clearing have not been adequately reserved by way of compensation.
Land clearing releases large volumes of greenhouse gases into the atmosphere, particularly carbon dioxide sequestered in trees (Chapter 6). The relationship between fire and greenhouse gases is complex; however reductions in the areal extent of fires and a shift to those with lower combustion efficiency (because the grass is still green) offers great potential to reduce emissions of the trace but very potent greenhouse gases methane and nitrous oxide.
The major threat to the persistence of eucalypts in northern Australia is land clearing (Chapter 7). Climate change may pose a substantial threat to some populations in the future. Local reduction in populations may occur because of rainforest expansion, over-harvest for didgeridu production, and frequent intense fires driven by invasive Gamba Grass.
savanna on elevated sandstone near Timber Creek
The most important findings of the study are outlined below, with recommendations.
A. Priorities for reservation
Our analysis shows that the reserve system in northern Australia is selective and often severely inadequate in its coverage. We recommend that on-ground conservation efforts through reservation focus on the following priorities:
- eucalypt taxa threatened by past, present and impending land-clearing (IUCN criteria A and B) or whose rarity in itself poses a threat to their persistence (IUCN criteria B and D). See Table 12 for a list of currently-threatened taxa;
- eucalypt communities threatened by past, present and impending land-clearing. See Figs. 33B and 34B, and Worksheet communities in the Supplementary file, for communities already subject to extensive clearing; and
- eucalypt taxa and communities that are poorly reserved regardless of past or impending threats. Foci for attention include:
- the very low level of reservation in inland (mostly pastoral) districts in all states and territories (Fig. 34A), and of the species-rich Einasleigh Uplands in north Queensland.
- those extremely restricted taxa located in the central and north Kimberley and in the White Mountains area south-west of Charters Towers in Queensland that are poorly reserved;
- all restricted taxa (i.e. all except rank 5, Table 6) – see worksheet restricted range in the Supplementary file – that are poorly reserved;
- the 11 species and three subspecies endemic to the study area that not represented in any conservation reserve, and the further 52 endemic species and ten endemic subspecies that have reservation indices of less than 30% (Fig. 25); and
- the 12 of 84 eucalypt communities (Map Units) that are not represented in any conservation reserve, and the further 40 of these Map Units that that have reservation indices of less than 10% (and often less than 1%) (Fig. 33A).
Key responsibilities: conservation efforts could include protection via both crown and private reserves. State and territory governments and their agencies have prime responsibility, while the Australian Wildlife Conservancy, Bush Heritage Australia and Indigenous groups can also play a substantial role.
B. Land clearing
Land clearing is the single greatest threat to the eucalypts of northern Australia (Chapter 7). The threat is past, present and impending.
Recommendations A1 and A2 above are most pertinent. Strategically, if agricultural intensification cannot be avoided then it must be linked to land use planning in which the eucalypts and eucalypt communities proposed for clearing are strongly matched by taxon and community, and to the extent possible geographically, by substantial and secure reservation.
Recognition and pricing of the carbon emissions involved in clearing, and in particular the provision of incentives for landholders based on the costs of emissions, is a tool with huge potential to reduce rates of land clearing and, in particular, to ensure that clearing of agriculturally marginal country does not occur.
With respect to carbon emissions, the key responsibility is for the Commonwealth government to facilitate the pricing of emissions of greenhouse gases and to do it in a way that enhances retention of native vegetation. A well-designed scheme offers significant advantages for many landholders, and their representative organizations can play a key role in lobbying the Commonwealth government to this end.
C. Threatened taxa and communities
Up-to-date listing of threatened taxa and communities is a key element to the appraisal of threatening processes, particularly land clearing, and in particular the appraisal of development proposals. All relevant jurisdictions, including the IUCN, accept nominations from the public. It is evident that these jurisdictions have not evaluated threats and nominated taxa and communities adequately. Nevertheless, a substantial body of relevant information and skill lies with jurisdictional agencies such as state and territory herbaria.
Key responsibilities: We recommend that:
- relevant state and territory agencies make all pertinent information available and assist in reviewing these data in more detail; and
- funds be sought to review these data in more detail and to prepare nominations for listing and de-listing under state, territory and Commonwealth legislation and in the IUCN Red List of threatened species.
A much better understanding of the ecology of eucalypts and eucalypt communities in northern Australia is required for proper management of threats and especially for land use planning where agricultural intensification is unavoidable. These research topics are fundamental to assessment and management of risks. We particularly recommend the following research topics:
- the reproductive ecology of eucalypts. Key issues include identification of supra-annual patterns and drivers of flowering and how these might be influenced by climate change; and identification of pollinators capable of providing this service at the relevant spatial scales;
- the landscape ecology of those pollinators capable of responding to infrequent mass-flowering of eucalypts, most notably the Little Red Flying-fox (Pteropus scapulatus) and Varied Lorikeet (Psitteuteles versicolor). For example, what level of connectivity is necessary for full maintenance of the ecosystem services they provide, and are there thresholds of habitat fragmentation beyond which pollination declines;
- aspects of the demography of eucalypts that remain poorly understood, including seedling establishment, the longevity of the seedling bank and of mature trees and how this varies with species, environments and disturbance across northern Australia;
- the evolutionary relationships among species in order to better understand the historical factors which have shaped the current distribution of species;
- field surveys of potentially threatened taxa to determine their distribution and abundance;
- field surveys of remote areas, particularly in the Kimberley and any others with a poor collection record (e.g. many inland areas), to locate new taxa and fill in our knowledge of the distribution of known taxa;
- more accurate (i.e. locally applicable) estimates of the emission of greenhouse gases resulting from land-clearing to properly cost the consequences of that clearing;
- the consequences of climate change for eucalypts; and
- identification of Evolutionary Significant Units for the conservation of north Australian eucalypts with both general application and particular relevance to the ability of species to cope with and respond evolutionarily to climate change. ESUs may be identified on the basis of geographic isolation, genetic distinctness or locally-adaptive features.
Key responsibilities: re-prioritisation of research to address key elements of basic ecology is required by universities and research-funding agencies. Further funding is required particularly from state, territory and Commonwealth governments.