Last year, TOP researchers published new policy-based population projections for the European Union. In a new companion piece, we explore the impacts of alternative immigration policies on two important EU environmental goals: reduction of greenhouse gas emissions and improved biodiversity conservation. We find that in both cases, less immigration, leading to smaller populations, will make success more likely. Realizing the environmental benefits of smaller populations, however, will depend on putting in place the right policies and management strategies to maximize the gains made possible by fewer people.
by Phil Cafaro and Frank Götmark
Europeans suffer from demographic complacency. Despite living in some of the world’s most densely populated countries in a time of obvious global ecological overshoot, they are more likely to worry about low birthrates and falling national populations than overpopulation. Our previous article, “Policy-based Population Projections for the European Union: A Complementary Approach,” established that immigration levels will make a big difference to future EU population sizes (table 1). For example, at status quo immigration levels, the United Kingdom’s population will increase 24% by 2100, while if levels are doubled, it will instead increase 68%. For the EU as a whole, current immigration levels will lead to a 10% percent population decrease by 2100, reducing net immigration to zero will accelerate that decrease (to 38%), while doubling immigration levels will instead increase the population by 10%.
Table 1. Status quo annual net migration numbers (average from 1998-2017) and percentage change from current population by 2100 under different migration scenarios. Source: Cafaro and Dérer, “Policy-based Population Projections for the European Union: A Complementary Approach.”
Clearly, EU immigration levels will make a substantial difference to population numbers in the future. But how important are those differences in terms of environmental impacts and achieving EU environmental policy goals? Our new publication, “The Potential Environmental Impacts of EU Immigration Policy,” seeks to quantify these impacts specifically regarding greenhouse gas (GHG) emissions and biodiversity conservation.
Greenhouse gas emissions
Since we don’t know how successful the nations of the EU will be in decreasing their per capita carbon emissions, we considered how five plausible immigration scenarios (zero net migration, ½ status quo net migration, status quo net migration, 2X status quo net migration, and 4X status quo net migration) would influence the total reductions achieved this century under three plausible emissions reduction scenarios (50%, 70%, and 90% per capita GHG reductions). Table 2 shows the results for the EU’s five most populous countries and for the EU as a whole. In every case, higher immigration leads to substantially higher population numbers, which in turn lead to substantially greater cumulative GHG emissions.
Table 2. Cumulative GHG emissions in gigatons, 2016-2100, for the five most populous EU countries and the EU as a whole, under three per capita emissions reduction scenarios and five net migration scenarios. Immigration changes are phased in over 10 years, per capita emissions reductions are phased in linearly over the course of the century. Source: Cafaro and Götmark, “The Potential Environmental Impacts of EU Immigration Policy.”
|Zero net migration||½ status quo||Status quo||2X status quo||4X status quo|
|Per capita emissions decrease 50% by 2100|
|Per capita emissions decrease 70% by 2100|
|Per capita emissions decrease 90% by 2100|
For example: under the 70% per capita emissions reduction scenario, cumulative emissions would be 18% less for Germany if it halved net migration compared to doubling it. The impact of immigration numbers on cumulative emissions decreases with faster per capita emissions reductions. But even under the optimistic 90% per capita emissions reduction scenario, the impact of changing immigration levels remains substantial.
One important result is that possible changes in immigration levels appear to have about as powerful an impact on cumulative GHG emissions as possible changes in per capita emissions. For example, decreasing Germany’s per capita emissions 90% rather than 50%, while keeping immigration at current levels, leads to 15.7 gigatons fewer emissions by 2100; while the difference between reducing German net migration to ½ current levels and increasing it to 2X current levels spans 13.5 gigatons at 50% per capita reductions. For the EU as a whole, cumulative emissions under a 4X status quo migration/90% per capita emissions reduction scenario would be more than cumulative emissions under a zero net migration/50% per capita emissions reduction scenario: 259 versus 243 gigatonnes CO2e, respectively.
These results suggest that population size will play an important role in the efforts of individual EU nations and the EU as a whole to meet their GHG emissions reduction goals, and that immigration policy could play an important role in facilitating or undermining such efforts.
As with climate change, population growth has been identified as a main factor causing biodiversity loss in many nations. Conservation biologists agree that habitat loss and degradation is by far the leading cause of biodiversity loss, and a recent study found that population increases contributed significantly to urbanization and habitat loss in western Europe in recent years. Increased human numbers have also been shown to amplify other important factors driving biodiversity loss, including agricultural intensification and conversion of natural forests to production forests.
Conversion of boreal forest in Sweden over time
While quantifying loss of biodiversity and species populations in relation to human population changes cannot be done as easily as for GHG emissions, the evidence suggests that future EU population numbers could greatly influence the success of efforts to protect biodiversity in the EU. Our five alternative immigration scenarios lead to great variation in future population densities in Europe (table 3).
Table 3. Population density (inhabitants per km2) and percentage change in density: current (2016) and in 2100 under five migration scenarios. Source: Cafaro and Götmark, “The Potential Environmental Impacts of EU Immigration Policy.”
|Current inhabitants per km2||
|Zero net migration||½ status quo||Status quo||2X status quo||4X status quo|
Just as every extra individual, now and in the future, will generate some GHGs and thus help heat Earth’s climate, with more individuals generating greater climate change; so every extra individual, now and in the future, will take some habitat and resources away from other species, with more individuals generating greater loss of biodiversity. While the complexity of the phenomena prevents us from affirming a strict 1:1 inverse relationship, the overall trend is clear: greater human numbers reduce biodiversity. Based on evidence from many studies that we reviewed (see table 6 in Cafaro & Götmark 2019), we can sketch the broad impacts of different immigration levels, and changing human population densities, on biodiversity protection in the EU (table 4, below).
In the absence of convincing evidence to the contrary, what holds true for climate change and biodiversity loss can be presumed to hold true more generally. Population size will play an important role in the efforts of EU nations to meet their future environmental challenges. Reducing immigration, and thus overall population numbers, can help create ecologically sustainable societies that share the landscape generously with other species, while increasing immigration will raise population numbers and tend to move EU nations further away from these goals.