Reptiles in the regrowth

What’s the value of regrowth vegetation?

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Last year the Queensland Government introduced legislation that removed protection for several categories of regrowth vegetation. Previously, regrowth which had not been cleared since 1989, and occurred in ecosystems with less than 30% of their original extent remaining, was protected from most clearing activities (Queensland Government, 2011). This protection has now been removed. WWF has calculated that, as a result of these changes, 700,000 ha of previously protected high-value regrowth can now be cleared for ‘high-value agriculture’ in Queensland (Taylor, 2013). These changes suggest that production has absolute priority over biodiversity and ecosystem function. Many claim these changes represent a significant blow to biodiversity and ecosystem restoration in Queensland.

This begs the question, why were these regrowth protections set up in the first place? At the end of the 20th century, vegetation in Queensland and New South Wales was cleared at rates similar to the rainforests of Brazil. In fact, for most of the 20th Century it was a condition of holding a lease, that the lessor cleared a proportion of the leased land to ensure they retained the lease. This program was so effective that by the turn of the 21st century, 45% of Queensland’s regional ecosystems were reduced to less than 30% of their original extent; a level that puts those ecosystems at risk of losing biodiversity and function. In 2004, Queensland enacted new vegetation laws that significantly reduced the rates of clearing. The thinking at the time was that the only way to increase the extent of these threatened ecosystems was to protect regrowth and allow it to mature.

“When the goal is to increase biodiversity in a disturbed landscape, passive regrowth woodlands offer cost-effective and valuable complementary habitat to remnant woodlands.”

 Excellent restoration potential

The most heavily cleared areas of Queensland are the woodlands of the Brigalow Belt Bioregion. Australian woodlands possess a rich diversity of reptiles, and reptiles are an important component of these nutrient-poor ecosystems because they ensure energy and nutrient flow between invertebrates and higher order predators. Our research in the Brigalow Belt Bioregion has shown that there is no difference in the diversity, dominance and composition of reptile communities in regrowth and remnant woodland (Bruton et al., 2013).

The sand goanna uses fallen timber in regrowth woodlands for shelter and for thermoregulation (basking). (Photo by Melissa Bruton)

The sand goanna uses fallen timber in regrowth woodlands for shelter and for thermoregulation (basking). (Photo by Melissa Bruton)

In fact, reptile communities in regrowth woodlands were indistinguishable from their corresponding communities in remnant woodlands. The most interesting part is that the regrowthwoodlands in our study were relatively young – between 10 and 23 years old – with only half the canopy height of remnant areas. In other words, for the reptiles we studied, regrowth doesn’t have to be ‘old’ to possess equivalent habitat value to remnant vegetation.

Queensland’s woodlands are dominated by acacias (wattles). The Brigalow Belt, for example, is named after one of its common wattles, Acacia harpophylla, or Brigalow. Acacias naturally sucker (send up shoots from roots left in the ground). This means a cleared site can quickly regrow, offering cost-effective, large-scale opportunities to restore ecosystems and reduce the biodiversity declines that have been caused by the over-enthusiastic clearing of vegetation. By comparison, many of the restoration efforts in southern Australia, and other parts of the world, require planting and follow up management, which generally limits them to small-scale efforts.

Achieving global restoration targets

Developing cost-effective restoration programs for threatened ecosystems will become increasingly important if the world is to meet the United Nations target of restoring 150 million ha of disturbed and degraded land globally by 2020 (a target endorsed at the 2012 United Nations Rio+20 Conference on Sustainable Development, see Decision Point #68).

When the goal is to increase biodiversity in a disturbed landscape, passive regrowth woodlands offer cost-effective and valuable complementary habitat to remnant woodlands. Our finding that regrowth is a high value habitat for reptile communities provides valuable information that will assist in the cost-efficient recovery of highly modified and reptile-rich subtropical woodland regions. In addition to the Brigalow Belt of Australia, these regions include the Chaco and Cerrado of South America; regions that also have been identified as opportunity areas for landscape restoration as part of the United Nations restoration goal.

The former vegetation management laws in Queensland acknowledged the financial value of passive regrowth vegetation by protecting regrowth areas in threatened ecosystems from clearing, allowing them to regenerate naturally. Unfortunately, the recent reforms by the current Queensland Government removed this legal protection.

What’s the trade-off?

The protection of high-value regrowth in Queensland has been traded for the expansion of ‘high-value agriculture’. However, at no point in the Vegetation Act 1999, or subsequent amendments, is ‘high-value agriculture’ defined. So what are we really trading?

Some definitions in the scientific literature suggest ‘high-value agriculture’ relates to ‘non-traditional food crops which have a higher commercial value’. Our only traditional food crops in Australia are the macadamia nut and bush tucker. Does this mean that ‘high-value agriculture’ refers to all other agriculture? It’s hard to know without the state government providing a formal definition, but if it is referring to all non-traditional agriculture then these reforms have effectively removed all protection from high-value regrowth.

If we take a commercial approach and define ‘high value agriculture’ as the top five Australian agricultural exports (by value) for the last financial year (2011-2012), then we are looking at wheat, beef, cotton, wool and wine. If so, then once again, the changes have effectively removed protections for the vast majority of high-value regrowth in Queensland, particularly for the woodlands of the Brigalow Belt and Mulga Lands Bioregions.

A Woma python in mulga regrowth. (Photo by Melissa Bruton)

A Woma python in mulga regrowth. (Photo by Melissa Bruton)

In either case, it would seem that scientific consultation regarding the impacts of the proposed amendments to regrowth legislation on agricultural production, the environment and society, have not been considered evenly, or in any depth. Studies such as ours are suggesting there are strong arguments to protect high value regrowth in the interests of biodiversity conservation.

Reptiles and remnants

Whilst our findings demonstrate that passive regrowth areas can effectively contribute to the amount of high quality habitat available for reptile communities in disturbed subtropical woodlands, the conservation of existing woodlands must always be considered a priority.

The sites that we surveyed in disturbed areas (cleared and regrowth) during this study were all within 700 m of remnant woodlands. Therefore, the opportunity for recolonisation from remnant vegetation was high in both cleared and regrowth sites. However, cleared sites remained species poor, confirming that these areas are not suitable habitat for most woodland reptile species.

In contrast, regrowth woodlands were recolonised at the time of our surveys. These findings suggest that regrowth areas that are adjacent to remnant woodlands should be prioritised for protection. Currently, there is insufficient landscape-level information available about the dispersal of reptiles across different matrices to determine if isolated regrowth areas are able to support a functional assemblage of woodland reptiles.

However, from what is now known about reptiles in subtropical woodland regrowth, we believe there is a compelling case to reinstate the legislative protection that has recently been overturned.

More info: Melissa Bruton melissa.bruton@uqconnect.edu.au

References

Queensland Government (2011). Regrowth Vegetation Code – on Freehold and Indigenous Land and Leasehold Land for Agriculture and Grazing. Version 2. Department of Environment and Resource Management.

Taylor MFJ (2013). Bushland at risk of renewed clearing in Queensland. World Wildlife Fund – Australia, Sydney.

Bruton MJ, CA McAlpine & M Maron (2013). Regrowth woodlands are valuable habitat for reptile communities. Biological Conservation 165: 95-103.

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