page_title: Dispersal of invasive species by ballast water
section_title: Ballast water
hierarchical_section_title: Dispersal of invasive species by ballast water / Ballast water
context_page_description: The dispersal of invasive species by ballast water refers to the unintentional introduction of invasive species to new habitats via the ballast water carried by commercial shipping vessels. Ballast water spreads an estimated 7000 living species to new habitats across the globe. These species can affect the ecological balance of their new regions by outcompeting native species or otherwise impacting native ecosystems.
context_section_description: The purpose of ballast water is to provide transverse stability, improve propulsion and maneuverability, and to compensate for weight loss due to fuel and water consumption. Approximately 10 billion tons of ballast water is transported each year, accounting for 90% of our world trade. Typically, ballast water discharge contains a variety of biological materials including non-native, invasive, and exotic species that can cause extensive ecological and economic damage to aquatic ecosystems. 
  Throughout this process, large ships withdraw up to 20 million gallons of water at their specific loading ports. Including native species; both plant and animal, before disposing them at their next destination.  However, when these invasive species are unloaded, specific conditions like temperature, salinity, lack of resources, and predator-to-prey competition affects how foreign species survive in non-native habitats. These factors cause stress within the ecosystems, throwing off ecological and environmental balance.
  As new species are introduced to non-native ecosystems, interspecific competition often becomes more intense. If native species are outcompeted by invasive species, it can affect the established predator-prey relationships within that region, possibly having disruptive effects on the wider food web.
caption: Diagram depicts invasive species being transported to and discharged into non-native habitats.