Saturday 30 January 2016

The fragility of life - are the aliens dead ?

Figure 1: Scenarios A) B) and C)
Despite the realisation that there are literally billions of stars, exoplanets, planets and other celestial bodies in the Universe, the perplexing reality is that proof of life on other planets has been impossible to obtain despite decades of effort. Programs such as SETI and observational work through telescopes (Hubble, Spitzer, Kepler and in the future TESS and James Webb) has done little to establish the existence of life on another planet. 

Chopra and Lineweaver, in a controversial paper, have proposed a Gaian bottleneck theory to explain the low or non-existence of life while making the telling observation that archaeological excavations have not unearthed alien spaceships and optical and radio searches for extraterresttrial intelligence have not been successful.

The Gaia hypothesis, (theory or principle), contends that organisms interact with their inorganic surroundings on Earth to form a self-regulating complex system that plays a critical role in maintaining the conditions for life on the planet. Within this paradigm are key components such as the way in which the biosphere and the evolution of life forms affect the stability of global climate, ocean salinity, oxygen in the atmosphere and other environmental variables that affect the habitability of the planet.

According to Chopra and Lineweaver, a Gaian bottleneck exists whereby if life emerges on a planet, it only rarely evolves quickly enough to provide activities which regulate greenhouse gases and albedo, thereby maintaining surface temperatures compatible with liquid water and habitability. This bottleneck theory therefore suggests that first, extinction is the cosmic default for most life on the surfaces of wet rocky planets and second, rocky planets need to be inhabited to remain habitable. Almost a Catch 22 situation.

The emergence of life's ability to modify its environment and regulate initially abiotic feedback mechanisms is termed 'Gaian regulation'. As far as Chopra and Linewear are concerned, without rapid  evolution of Gaian regulation, early extinction would be the most common outcome for planetary life. As continuing efforts are made to search the universe to locate and identify life, the Gaian bottleneck model suggests 'that the vast majority of fossils in the Universe will be from extinct microbial life.'

Three scenarious are shown in Fig 1 above - A) Emergence bottleneck, life rarely emerges even on rocky wet planets; B) No bottleneck, life emerges with high probability and lasts for billions of years; C) Gaian bottleneck, life emerges but goes extinct within a billion years.

So, the chances of finding any form of life, under this model is close to zero and what evidence may be found will have long been dead. 

Chopra and Lineweaver's paper can be accessed here:


Gas and dust form planetary disks - formation - image courtesy NASA

Wednesday 27 January 2016

The value of National Parks - a timeless heritage

Dove Lake, Cradle Mountain - Lake St Clair National Park, Australia (c) SO
National Parks, those precious territories of conservation, can be found world-wide across Africa, Asia, South America and Europe but they originated in just two countries - the United States and Australia. The first national park to be proclaimed was Yellowstone in the US in 1872, the second being the Royal National Park in Australia in 1879. Since then the concept has been introduced across the world but with vastly differing results and often severely challenged by land use conflict for human activity.

Australia now has over 500 national parks with over 28 million hectares of land designated as national parkland accounting for almost four per cent of Australia's land areas. A further six per cent of Australia is protected under various land categories such as state forests, nature parks and conservation reserves.

As at 2015, Australia has 19 World Heritage areas, a number of which also encompass national parks. Tthe United Nations Educational, Scientific and Cultural Organization (UNESCO) lists areas and structures as World Heritage when they are deemed worthy of special protection due to representing the best examples of the world's cultural and natural heritage. It's something of a mixed blessing for a number of World Heritage sites have also been lost due to war and religious conflict demonstrating that protection was little more than a theoretical concept

The key World Heritage sites in Australia with a nature significance are listed below:
  • Great Barrier Reef (inscribed 1981)
  • Kakadu National Park (inscribed 1981)
  • Willandra Lakes Region (inscribed 1981)
  • Lord How Island Group (inscribed 1982)
  • Tasmanian Wilderness (inscribed 1982)
  • Gondwana Rainforests of Australia (inscribed 1986)
  • Uluru-Kata Tjuta National Park (inscribed 1987)
  • Shark Bay (inscribed 1991)
  • Fraser Island (inscribed 1992)
  • Australian Folssil Mammal Sites (Riversleigh, Naracoote) (inscribed 1994)
  • Heard and McDonald Island (inscribed 1997)
  • Macquarie Island (inscribed 1997)
  • Greater Blue Mountains Area (inscribed 2000)
  • Purnululu National Park (inscribed 2003)
  • Ningaloo Coast (inscribed 2011)
The key challenge is matching conservation with public access for it's becoming more apparent that its possible for national parks to become too popular leading to large volumes of people traversing the fragile ecosystems and habitats with resultant degradation of the natural environment.
Freycinet National Park, Australia (c) Sentinel Owl