Predicting the future is a tricky business. As then United States Secretary of Defence Donald Rumsfeld famously said “There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know” . Then there is the interactions between all the variables that determine the outcome of a particular event. However, few things work in isolation and species decline often results from the accumulation of different stressors. If we want to put in place conservation management measures that are effective in the long term, then we need to be able to put our known (and measurable) stressors together and figure out what, cumulatively they mean for our potentially at risk species. The shy albatross (Thalassarche cauta) is an endemic to Australia, breeding on just three Tasmanian islands, including the aptly named Albatross Island.
The albatross of Albatross Island have a long history of human interest. In the early 19th century adult albatross were extensively hunted for their feathers and egg, taking their numbers down from an estimated 11,100 pairs to just 400. The population is now recovering, but still faces a number of possible threats. High on this list are two issues – changing climatic conditions, and the accidental capture of the albatross in longline and trawl fisheries. To understand just what the combined impact of these stressors could mean for this vulnerable bird, Robin Thomson and colleagues from CSIRO Marine and Atmospheric Research, together with the Tasmanian Government Department of Primary Industries, Parks, Water and the Environment (DPIPWE) put together a model that can hopefully direct management to ensure these birds survive in the long term.
Building a model Models need data, and fortunately the researchers were able to access some good sources. Fishing effort from longline and trawls was obtained from the Australian Fisheries Management Authority. There isn’t much in the way of specific data on actual bycatch levels of the albatross, so instead the researchers used the best available data they had to make a conservative estimate of the level of bycatch. Data on the albatross themselves came from two sources. In 1980, the DPIPWE started an annual monitoring program of the albatross, providing the researchers with 20 years-worth of data. DPIPWE also undertook some foraging studies which, alongside data from BirdLife Internationa, provided tracking data (e.g. where the birds went whilst at sea) which could be used to see where fisheries and the birds overlap. For environmental variables, they used a host of different sources to obtain historical information on rainfall, maximum daily temperatures, sea surface height anomaly, as well as climate projections. The researchers set about building a seabird population model, and placed it into an “integrated modelling framework”, which essentially involves using a variety of equations and statistical analysis to see what the population of albatross might look like in the future. If you are interested in how models are created, have a read of the methods section in the open access paper (see link below).
All models are wrong, (but some are useful) The thing about models is that they are a simplified version of what really happens in the real world. We put in the data we have, and try replicate something very similar to what we observe in the real world. For the stuff we know about but have no data on… well that can be exceedingly tricky if not impossible to put into a working model. As for the stuff we don’t know about… well no model can be perfect. The researchers highlight a number of things that they would have liked to be able to model better. This includes the level of shy albatross bycatch, but also other factors like disease, especially avian pox which has historically impacted the breeding colony. Despite these issues, the model does stand up to what we have seen in the real world, producing results that could be validated with actual observations (hindcasting).
(All models are wrong) , but some are useful. AKA What did we learn? The model was able to confirm that both the climate crisis and the estimated bycatch levels do impact the population of albatross. Crucially the model also showed that with our changing climate, the situation is likely to get worse for the shy albatross, primarily because increasing temperatures and increasing rainfall are likely to hamper breeding success. Even if we were to address all of the anthropogenic causes of the climate crisis overnight, climate change will still happen because there is a lag between our actions and how the climate reacts. Fortunately all is not lost, and with good fisheries management we can help the shy albatross of Albatross Island out. Reducing bycatch is a very good move for this population of ocean wanderers. How much we need to reduce the bycatch by is a good question, and one answered by the model – around 50%. Exactly how this could be achieved is another topic altogether.
Read the research for yourself The paper was published in the open access journal PLOS ONE. You can have a read of the research yourself by heading here http://dx.doi.org/10.1371/journal.pone.0127006.