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  • Rights: The University of Waikato
    Published 15 April 2009 Referencing Hub media

    In this video, 4 New Zealand scientists – Dave Campbell, Louis Schipper, David Hamilton and Keith Hunter – talk about how the water cycle is part of Earth’s system. They point out that Earth’s system consists of 4 subsystems – the geosphere, hydrosphere, atmosphere and biosphere – which all interact with each other.

    In the past, scientists used to think of Earth’s subsystems as working in isolation. In recent times, however, they have realise how important one system is to another.

    When you watch this video, note when the scientists draw attention to where systems overlap. (Dave Campbell is talking about the biosphere extending into the atmosphere and geosphere.)

    Jargon alert
    Paradigm – a set of concepts or models.


    I think the most important paradigm that we've… well, the most important new idea that we've come up with in the last 20 or 30 years, is that you can't look at things like the physics of the ocean, the chemistry of the ocean, the biology of the ocean, as separate things that happen. They are all really closely interlinked, so we think of the Earth as a system.

    Earth is a system that is broken into a number of subsystems – the geosphere, the biosphere, the hydrosphere and the atmosphere

    The atmosphere and the geosphere are fairly distinct, but I guess people think that the biosphere is very much just what we see on the surface of the land. And in actual fact, the biosphere extends a lot higher up into the atmosphere, and a lot deeper under the ground than what we think. Geologists and groundwater scientists find bacteria living in groundwater systems hundreds of metres underneath the Earth's surface, and a strange fact is that bacteria play a very active role in the precipitation process. So some sorts of bacteria are important for causing cloud droplets – that are microscopic little droplets of water that are in clouds – to freeze. Without bacteria, it’s very difficult for droplets in clouds to freeze. So the biosphere can extend quite high up into the atmosphere.

    The Earth's subsystems are interconnected by processes and cycles. Over time, they store, transform and transfer matter and energy throughout the whole Earth system, and react with each other. An example is when rains hits land.

    Water from rain comes down onto the land and the soil and the plants growing on it, and it is important that water can infiltrate it, and then be held by soil so that the plants can then access it. If that water just flows through down into groundwater, the plants are not going to be able to grow on it, and it’s not going to be able to support forest, or plants and animals – that sort of thing. So the soil has to be able to hold onto that water, and when it rains, the water predominantly ends up in smallest holes first. That is where it’s stored, and that is because those small pores can hold onto water really quite tightly.

    Well it could take up to 140 years for the water to actually seep through into the groundwater, through the soil and reach the lake, and it may enter directly into the lake or it may create a spring that then feeds into the lake.

    These interactions between the different subsystems, such as the hydrosphere and the geosphere, are a response of each system to maintain its stability. As a result, the Earth’s system is complex and dynamic.

    Dr David Campbell, Waikato University
    Prof. Keith Hunter, Otago University
    Prof. Louis Schipper, Waikato University
    Prof. David Hamilton, Waikato University
    Flyover NZ/Rotorua Lakes model by Mathew Allan
    Cirrus and cumulus cloud images, Edward Hyde
    Streaky sky image, Brenda Anderson
    Cumulonimbus image, Philip Norton
    Edward Hyde
    Mud puddle image, Dr Ravi Gooneratne, Lincoln University
    Cow footage, Dexcel and the New Zealand Biotechnology Hub

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