New Zealand's 50,000 km2 dryland zone covers rain shadow areas east of the main axial ranges of both main islands, and accounts for 19% of New Zealand's land area.
Dryland environments contain some of the most transformed, least protected and most threatened native ecosystems and species in New Zealand. A significant proportion (>70%) of indigenous habitat has been lost, and only 1.9% of the zone is now legally protected. Consequently, drylands contain an exceptionally high proportion of New Zealand's most threatened species (e.g. 46% of acutely threatened and 53% of chronically threatened vascular plants; Rogers et al. 2004; Walker et al. 2005). Endemic dryland iconic species such as grand and Otago skinks face extinction within ten years under current environmental pressures. Many more indigenous species are regionally threatened, concentrated in small refuges, with reduced regeneration, compromised genetic structure, and limited resilience, and are progressively disappearing from regional gene pools. Although strongly modified from their original states, remaining dryland communities and species are of major significance, representing all that remains of a unique and diverse ecological zone and its potential for restoration.
Why do we want to restore woody communities?
Today's mixed native-exotic dryland communities are newly created (<800 years old), unstable, and derived from fire-sensitive shrubland and dry forest ecosystems (McGlone 2001; Walker et al. 2004). With reductions in fire and grazing, many will naturally succeed back to a variety of woody states, generally without passing back through tussock grassland. These novel woody communities will be mixtures of native and exotic species, with variable trajectories of change depending on local seed sources, dispersal agents, pests and weeds.
The recovery of structurally complex woody vegetation in drylands is likely to provide native species with increased food sources, shelter from climatic extremes, better refuge from predators, and lower rabbit numbers and therefore fewer large predators (Norbury 2001). Therefore, emerging woody dryland communities should support a greater diversity of fauna and flora, and the need for conservation intervention to maintain many threatened species should be reduced. We also expect woody communities to restore more natural ecosystem function (nutrient cycling, litter and soil organic matter accumulation, carbon sequestration, water storage and yield) and resist weed invasion better than open grasslands.
The research needed
Increased ecological research in drylands over the last 5-7 years has begun to address aspects of ecological history, conservation status and likely future trajectories. However, we still lack the basic ecological and practical knowledge and capacity to reverse dryland biodiversity decline (Walker et al. 2005). In this research programme, we will build understanding of dryland woody species ecology (present distributions, succession pathways and rates, traits, and factors that control and limit their spread). We will apply this knowledge to develop and test low input methods for facilitating native woody succession in the field. The bird, lizard, invertebrate, and plant biodiversity associated with woody communities across the dryland zone will be surveyed and quantified, so that we can better understand benefits and drawbacks of woody succession, and predict some of the changes that will occur in indigenous communities as succession proceeds. We will also work alongside an aligned Landcare Research project (Multiple Pests Dynamics), which seeks to understand the interactions among pests that impact indigenous biodiversity in dryland ecosystems.
Raising community and agency awareness
A significant barrier to achieving conservation gains in many dryland areas is low public awareness and appreciation of the indigenous biota, the threats they face, and the potential for their recovery. Unlike forests, dryland ecosystems have an image problem. They are traditionally viewed as agricultural production systems. Native shrublands are commonly referred to as ‘grey shrublands’ - hardly inspiring! Another barrier is lack of awareness and political will by some territorial authorities to protect native biodiversity on private land. With the Department of Conservation’s assistance, we are trying to help communities and agencies by encouraging them to develop biodiversity protection programmes, giving public lectures, public field tours, displays in museums, media statements, submissions to Long Term Council Community Plans, assisting with Conservation Management Strategies, and raising the profile of iconic fauna.