Glossary of Environmental Science - R

R

• radiative forcing - changes in the energy balance of the earth-atmosphere system in response to a change in factors such as greenhouse gases, land-use change, or solar radiation. Positive radiative forcing increases the temperature of the lower atmosphere, which in turn increases temperatures at the Earth's surface. Negative radiative forcing cools the lower atmosphere. Radiative forcing is most commonly measured in units of watts per square meter (W/m2).
• rain garden – an engineered area for the collection, infiltration and evapotranspiration of rainwater runoff, mostly from impervious surfaces; it reduces rain runoff by allowing stormwater to soak into the ground (as opposed to flowing into storm drains and surface waters which can cause erosion, water pollution, flooding, and diminished groundwater). They can also absorb water contaminants that would otherwise end up in water bodies. The terminology arose in Maryland, USA in 1990s as a more marketable expression for bioremediation.
• rainwater harvesting – collecting rainwater either in storages or the soil mostly close to where it falls; the attempt to increase rainwater productivity by storing it in pondages, wetlands etc., and helping to avoid the need for infrastructure to bring water from elsewhere. Practiced on a large scale upstream this reduces available water downstream.
• rangeland – a region where grasing or browsing livestock is the main land use.
• raw materials - materials that are extracted from the ground and processed e.g. bauxite is processed into aluminium.
• reclaimed water - water taken from a waste (effluent) stream and purified to a level suitable for further use.
• recovered material – (waste) material that would have otherwise been disposed of as waste or used for energy recovery, but has instead been collected and recovered (reclaimed) as a material input thus avoiding the use of new primary materials.
• recovery rate – (waste) the recovery rate is the percentage of materials consumed that is recovered for recycling.
• recyclables – strictly, all materials that may be recycled, but this may include the recyclable containers and paper/cardboard component of kerbside waste (excluding garden organics).
• recycled content - proportion, by mass, of recycled material in a product or packaging. Only pre-consumer and post-consumer materials are considered as recycled content.
• recycled material – see recovered material.
• recycled water – treated stormwater, greywater or blackwater suitable for uses like toilet flushing, irrigation, industry etc. It is non-drinking water and is indicated using a lilac non-drinking label.
• recycling - a wide range of activities, including collection, sorting, reprocessing and manufacture of products into new goods.
• reforestation – the direct human conversion of non-forested land to forested land through planting, seeding or promotion of natural seed sources, on land that was once forested but no longer so. According to the language of the Kyoto Protocol, for the first commitment period (2008–2012), reforestation activities are limited to reforestation occurring on lands that did not contain forest at the start of 1990; replanting of forests on lands that have recently been harvested.
• regulating services – (sustainability) the benefits obtained from the regulation of ecosystem processes including, for example, the regulation of climate, water or disease.
• renewable energy - any source of energy that can be used without depleting its reserves. These sources include sunlight (solar energy) and other sources such as, wind, wave, biomass, geothermal and hydro energy.
• renewable energy certificates - Market trading mechanisms created through the Renewable Energy (Electricity) Act 2000 in connection with the commonwealth government's mandatory renewable energy target. The certificates provide a 'premium' revenue stream for electricity generated from renewable sources.
• reprocessing – (waste) changing the physical structure and properties of a waste material that would otherwise have been sent to landfill, in order to add financial value to the processed material, this may involve a range of technologies including composting, anaerobic digestion and energy from waste technologies such as pyrolysis, gasification and incineration.
• residual waste – (waste) waste that remains after the separation of recyclable materials (including green waste).
• resource flow - the totality of changes in multiple resource stocks, or at least any pair of them, over a specified period of time
• resource intensity – ratio of resource consumption relative to its economic or physical output; for example, litres of water used per dollar spent, or litres of water used per tonne of aluminium produced. At the national level, energy intensity is the ratio of total primary energy consumption of the country to either the gross domestic product, or the physical output (total goods produced).
• resource productivity – the output obtained for a given resource input.
• resource recovery – (waste) the process of obtaining matter or energy from discarded materials.
• resource stock - the total amount of a resource often related to resource flow (the amount of resources harvested or used per unit of time). To harvest a resource stock sustainably, the harvest must not exceed the net production of the stock. Stocks are measured in mass, volume, or energy and flows in mass, volume, or energy per unit of time.
• respiration – (biology) uptake by a living organism of oxygen from the air (or water) which is then used to oxidise organic matter or food. The outputs of this oxidation are usually CO₂ and H₂O; the metabolic process by which organisms meet their internal energy needs and release CO₂.
• retail therapy – using shopping to obtain a ‘lift’ to make up for other things lacking in our lives.
• retrofit - to replace existing items with updated items.
• reuse - the second pillar of the waste hierarchy - recovering value from a discarded resource without reprocessing or remanufacture e.g.clothes sold though opportunity shops strictly represent a form of re-use, rather than recycling
• risk – the probability of a (negative) occurrence.