This depicts bootstrapped 95 % confidence intervals:
ggplot(meltdf,aes(x=Year,y=value,colour=variable,group=variable)) +
stat_summary(fun.data = "mean_cl_boot", geom = "smooth")
This depicts the mean of all values of all variables +-1SD:
ggplot(meltdf,aes(x=Year,y=value)) +
stat_summary(fun.data ="mean_sdl", mult=1, geom = "smooth")
You might want to calculate the year means before calculating the means and SD over the variables, but I leave that to you.
However, I believe a boostrap confidence interval would be more sensible, since the distribution is clearly not symmetric. It would also be narrower. ;)
And of course you could log-transform your values.
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