While over-hunting was the primary cause for decline in walrus numbers over the 20th century, other human activities may also have an impact on walrus populations. Walruses are very sensitive to human caused environmental disturbances, such as the noise of boats and low-flying airplanes. Noise from increased industrial activity in the Arctic such as seismic surveys, exploration drilling, building of production facilities and other traffic related disturbances linked to oil exploration activities including helicopter transport and intensified shipping may potentially displace walruses from their wintering grounds or other important feeding grounds (Dietz et al. 2013). In the Canadian Arctic, walrus are likely to be exposed to greatly increased shipping associated with both reduced sea ice and increased exploration and extraction of minerals and hydrocarbons (DFO 2013b). Another concern is potential disturbance of walrus by scallop fishing off western Greenland, although the extent of the impact on walrus is not known (NAMMCO 2013). In Svalbard, increasing tourism is being monitored to ensure that it does not affect walrus distribution or behaviour.
Hauled out walruses disturbed by noise may panic and flee, which can sometimes lead to the death of animals, especially calves, by trampling. Repeated disturbance may cause walrus to abandon an uglit, or haul out site, forever.
Walruses are quite conservative in their choice of habitat and food, so any reduction in either of these may have detrimental effects on their numbers. Walrus numbers could be threatened by a loss of sea ice caused by global warming and accompanying environmental changes, with retreating sea ice reducing the availability of suitable habitat and food supply, and affecting walrus movement and behaviour (Dietz et al. 2013). Changes in sea ice extent and location could also affect human hunting patterns, providing hunters easier access to walrus.
Another potential threat to walrus populations is pollution from oil and gas exploration and extraction activities. Walruses are particularly at risk from oil spills as their staple diet items of benthic invertebrates are known to accumulate hydrocarbons (Born et al. 1995). Other pollutants of concern are heavy metals, such as cadmium, lead and mercury. Elevated levels of these metals have been found in Atlantic walrus tissues, though it is not clear what effect these might have on walrus health (Born et al. 1995). Relatively high levels of organochlorines such as DDT and PCBs have also been found in those walruses that eat seals, although in a fairly recent study in Svalbard, levels of these compounds were found to be substantially lower than those of animals sampled in the same area 10 year earlier (Wolkers et al. 2006). A surprising result from the same study was that individual variation in contaminant levels and patterns was very high, even though the walrus sampled were from a homogenous group which consisted solely of adult males from a restricted geographic area (Wolkers et al. 2006).