Victoria Bonaparte bioregion Description Figure 2 WARMS (WA) and Tier 1 (NT) monitoring sites shown Area: 72 600 km2 on the pastoral tenure of The Victoria Bonaparte bioregion is found in Western both jurisdictions Australia (WA) and the Northern Territory (NT) and bioregion boundary includes dissected plateaus and alluvial plains and a NT pastoral tenure number of river basins. Eucalypt woodlands are the WARMS monitoring site dominant vegetation community. Tenure includes Tier 1 monitoring site pastoral leases, Aboriginal land and conservation Victoria reserves. The main industries are cattle grazing, Bonaparte 1 horticulture and tourism. Major population centres sub-IBRA are Wyndham and Kununurra in WA, and Timber Creek and Daly River in the NT. WA Location The Victoria Bonaparte bioregion crosses the NT–WA border south of the coast (74% of area is in the NT, 26% is in WA). Figure 1 shows the location of the WARMS (WA) and Tier 1 (NT) monitoring sites Victoria Bonaparte bioregion, while Figure 2 shows the Datashow nsources on the pasto raavailablel tenure of both jurisdictions location of Western Australian Rangeland Monitoring Data sources include: System (WARMS) and Tier 1 monitoring sites in WA and the NT, respectively. n WARMS, Victoria Bonaparte 1 (VB1) sub-Interim Biogeographic Regionalisation for Australia (IBRA) Figure 1 Location of the Victoria only, which provides moderate reliability for Bonaparte bioregion reporting change, with a small number of dispersed sites, quantitative data, and a focus on perennial species (which helps to filter short-term seasonal variability) n NT Tier 1, which provides low to moderate reliability, with a small number of sites with a patchy distribution, estimated data, and a focus on perennial herbage species n domestic stocking density, which provides moderate reliability n fire extent, intensity and frequency, which provides high reliability n dust Location of Victoria Bonaparte bioregion n distance from water Victoria Bonaparte bioregion 1 n distribution and relative abundance of invasive Number No animals and weeds of site- change: by-year Decline: 0.90 ≤ Increase: n land use Seasonal combi- frequency frequency frequency n conservation estate quality nations < 0.90 < 1.10 ≥ 1.10 Above n land values. average 12 17% 58% 25% Average 10 10% 60% 30% Climate Below average n/a n/a n/a n/a The climate of the Victoria Bonaparte bioregion is subtropical. Most of the annual rainfall occurs between Northern Territory November and March. Spatially averaged median (1890–2005) rainfall is 818 mm (April to March Tier 1, index based on composition (by biomass) rainfall year; see Figure 3). and cover of perennial herbage species Figure 3 Decile rainfall for the period Insufficient sites were assessed to report change 1991–1992 to 2004–2005 reliably following both above- and below-average seasonal quality. 10 9 8 Percentage of reassessed 7 Number sites showing: 6 median 5 of site- Decline: Increase: 4 by-year > 3 > 3 3 Seasonal combi- decrease No increase Rainfall decile 2 quality nations in index change in index 1 0 Above 1991-92 1993-94 1995-96 1997-98 1999-00 2001-02 2003-04 average 3 n/a n/a n/a Rainfall year Average 11 36% 36% 27% Annual rainfall is for the 12‑month period 1 April Below to 31 March. average 5 n/a n/a n/a Decile rainfall was above the median for most of the reporting period. The year 1991–1992 was very dry, Sustainable management as was 2002–2003. Critical stock forage Note that regional averaging of rainfall conceals spatial variability. Some parts of the Victoria Bonaparte WA, Victoria Bonaparte 1 sub‑IBRA bioregion may have experienced better seasonal quality and others worse during the 1992–2005 period. WARMS, frequency of decreaser perennial grass species Landscape function When seasonal quality was above average, 8% of sites showed a decline in the frequency of decreaser WA, Victoria Bonaparte 1 sub-IBRA perennial grass species. It is not possible to report change when seasonal quality was below average. WARMS, perennial grass frequency When seasonal quality was above average, 17% of sites showed a decline in perennial grass frequency. It is not possible to report change when seasonal quality was below average. 2 Rangelands 2008 — Taking the Pulse No Number change: 1.10 1.10 0.90 of site- Decline: 0.80 ≤ Increase: by-year richness richness richness Seasonal combi- index index < index quality nations < 0.80 1.20 ≥ 1.20 Seasonal Species frequency < Above quality group Number of site-by- year combinations Decline: frequency < No change: 0.90 ≤ Increase: frequency ≥ average 12 58% 33% 8% Above Decreaser 12 8% 50% 42% Average 10 10% 30% 60% average Intermediate n/a n/a n/a n/a Below Increaser n/a n/a n/a n/a average 0 n/a n/a n/a Average Decreaser 10 10% 60% 30% Intermediate n/a n/a n/a n/a Increaser n/a n/a n/a n/a Change in woody cover Below Decreaser n/a n/a n/a n/a Western Australia average Intermediate n/a n/a n/a n/a Increaser n/a n/a n/a n/a Crown cover of woody species increased by 13% on average, and remained the same or increased on Northern Territory 82% of WARMS sites. On no sites did cover drop below 50% of the initially recorded value. Tier 1, composition (by biomass) of palatable perennial (2P) herbage species Northern Territory No sites showed decline when seasonal quality was Based on the Australian Greenhouse Office definition 1 above average. It is not possible to report change and mapping of forest extent , there is some forest following below-average seasonal quality. cover in the NT part of the Victoria Bonaparte bioregion (7.60% of NT bioregion area in 1991, Percentage of reassessed increasing by 1.90% to 9.50% in 2004). There is good sites showing: coverage of Landsat data for reporting this result. Number Decline: Increase: of site- > 20% > 20% by-year decrease increase Distance from stock water Seasonal combi- in 2P No in 2P The percentage of sub-IBRA area within three quality nations grasses change grasses kilometres of permanent and semipermanent sources Above of stock water is summarised in the following table. average 20 0% 90% 10% Note that for WA, the locations of stock waterpoints Average 27 4% 59% 37% were sourced from state mapping of lease infrastructure, Below average 5 n/a n/a n/a and watered area is reported as the percentage of pastoral tenure within each sub-IBRA. NT data were obtained from Geoscience Australia’s GEODATA Plant species richness TOPO 250K vector product (Series 3, June 2006), This section reports for the Victoria Bonaparte 1 and watered area is the percentage of sub-IBRA area. sub-IBRA in WA only. These differences mean that the percentage watered area reported by each data type is not directly When seasonal quality was above average, 58% of comparable. WARMS sites showed a decline in species richness of native perennial plants. No sites were assessed when seasonal quality was below average. 1 See http://www.greenhouse.gov.au/ncas/reports/tech09.html Victoria Bonaparte bioregion 3 Western Northern Components of total Australia Territory grazing pressure % sub- % sub- IBRA % sub- IBRA % sub- within IBRA within IBRA Domestic stocking density 3 km of area 3 km of area Domestic stocking density data apply to the pastoral Sub-IBRA water analysed water analysed tenure of both WA and the NT. The grazed area of Victoria Bona- parte P1 (VB1) 9.5 64.9 2.0 100 the Victoria Bonaparte bioregion decreased from Victoria Bona- 62% in 1992 to 45% in 2001. Based on data from parte P2 (VB2) 8.3 100 the Australian Bureau of Statistics and taking account Victoria Bona- of the reduced area grazed over time, domestic parte P3 (VB3) 7.7 100 stocking density increased substantially over the IBRA = Interim Biogeographic Regionalisation for Australia; 1992–2004 period and was much higher than the VB = Victoria Bonaparte 1983–1991 average from 1998 onwards. Stocking density in 2001 and 2002 was 65% above the 1983– Note that this analysis does not include the locations 1991 baseline. The extended period of above-average of natural waters, which in this bioregion can provide seasonal quality (see Figure 3 of decile rainfall, above) many additional sources of water for stock, particularly probably contributed to increased stocking, particularly in the early dry season. It is not possible to report from 1997 onwards. Note that spatial averaging change in watered area for the 1992–2005 period conceals likely variation in stocking density trends for either jurisdiction. across the bioregion. Weeds Kangaroos Weeds known to occur in the Victoria Bonaparte There are no suitable data for reporting change in bioregion include: kangaroo populations. Common name ubs Bellyache bush Jatropha gossypifolia Invasive animals Calotrope Calotropis procera Invasive animal species known to occur in the Chinee apple Ziziyphus mauritiana Victoria Bonaparte bioregion include: Chinese violet Asystasia gangetica subsp. micrantha Common name Scientific name Grader grass Themeda quadrivalvis Feral pig Sus scrofa Hymenachne Hymenachne amplexicaulis Wild dog Canis spp. Hyptis Hyptis suaveolens Feral cat Felis cattus Lantana Lantana camara Cane toad Bufo marinus Mimosa Mimosa pigra Water buffalo Bubalus bubalis Mission grass Pennisetum polystachion Camel Camelus dromedaries Noogoora burr Xanthium occidentale Donkey Equus asinus Parkinsonia Parkinsonia aculeata Horse Equus caballus Prickly acacia Acacia nilotica subsp. See www.anra.gov.au for distribution maps indica Salvinia molesta Salvinia molesta Sicklepod Senna obtusifolia and S. tora Sida spp. Sida spp. See www.anra.gov.au for distribution maps 4 Rangelands 2008 — Taking the Pulse Products that support reporting The WA portion of the bioregion has Ramsar-listed of landscape function and wetlands (Biodiversity Working Group indicator: Wetlands).